//! Proposal pages (hub spec §7): list, new, detail with conversation,
//! changes and files, comments anchored to atoms, reviews, landing.

use super::history::{render_files, FileRows};
use super::settings::{csrf, require};
use super::{filters, lookup, lookup_role, Error, Page, RepoShell, Shell};
use crate::auth::{Access, Role, Viewer};
use crate::db::{self, accounts, proposals as pdb};
use crate::render::{self, diff};
use crate::repos::proposals::{self as pl, Projection, Source};
use crate::repos::view::{self, ChangeView, ConflictView};
use crate::repos::RepoName;
use crate::Shared;
use askama::Template;
use axum::extract::{Form, Path, Query, State};
use axum::response::{IntoResponse, Redirect, Response};
use hub_api::{Approval, ProposalSource, ProposalState};
use oxy_core::hash::ChangeHash;
use serde::Deserialize;
use std::collections::{BTreeMap, HashMap};

// ------------------------------------------------------------------ list

#[derive(Template)]
#[template(path = "proposals.html")]
pub struct ProposalsPage {
    shell: Shell,
    repo: RepoShell,
    rows: Vec<pdb::ProposalRow>,
    filter: String,
    counts: (usize, usize, usize),
    bookmarks: Vec<String>,
    q: String,
    sort: String,
    pager: super::Pager,
    labels: std::collections::HashMap<i64, Vec<db::issues::Label>>,
}

impl ProposalsPage {
    fn labels_of(&self, id: &i64) -> &[db::issues::Label] {
        self.labels.get(id).map(Vec::as_slice).unwrap_or(&[])
    }
}

#[derive(Deserialize)]
pub struct ListQuery {
    state: Option<String>,
    q: Option<String>,
    sort: Option<String>,
    page: Option<usize>,
}

/// The list's sort orders.
pub const SORTS: &[(&str, &str)] = &[("updated", "recently updated"), ("newest", "newest"), ("oldest", "oldest")];

pub async fn list(
    State(app): State<Shared>,
    viewer: Viewer,
    Path((owner, name)): Path<(String, String)>,
    Query(q): Query<ListQuery>,
) -> Result<Page<ProposalsPage>, Error> {
    let shell = Shell::new(&app, &format!("/{owner}/{name}/proposals"), &viewer);
    let (repo, row, role) = lookup(&app, &shell, &viewer, &owner, &name).await?;
    let all = pdb::list(&app.db, row.id, &[]).await.map_err(|e| Error::from_db(shell.clone(), e))?;
    let counts = (
        all.iter().filter(|p| p.is_open()).count(),
        all.iter().filter(|p| p.state == "landed").count(),
        all.iter().filter(|p| p.state == "closed").count(),
    );
    let filter = q.state.unwrap_or_else(|| "open".into());
    let mut labels: std::collections::HashMap<i64, Vec<db::issues::Label>> = std::collections::HashMap::new();
    for (id, l) in db::issues::labels_by_proposal(&app.db, row.id).await.map_err(|e| Error::from_db(shell.clone(), e))? {
        labels.entry(id).or_default().push(l);
    }
    // `author:bob label:ui target:main words…`
    let qtext = q.q.clone().unwrap_or_default();
    let (mut authors, mut wanted, mut targets, mut words) = (vec![], vec![], vec![], vec![]);
    for tok in qtext.split_whitespace() {
        match tok.split_once(':') {
            Some(("author", v)) => authors.push(v.to_lowercase()),
            Some(("label", v)) => wanted.push(v.to_lowercase()),
            Some(("target", v)) => targets.push(v.to_string()),
            _ => words.push(tok.to_lowercase()),
        }
    }
    let mut rows: Vec<pdb::ProposalRow> = all
        .into_iter()
        .filter(|p| match filter.as_str() {
            "open" => p.is_open(),
            "landed" => p.state == "landed",
            "closed" => p.state == "closed",
            _ => true,
        })
        .filter(|p| authors.is_empty() || authors.contains(&p.author.to_lowercase()))
        .filter(|p| targets.is_empty() || targets.contains(&p.target))
        .filter(|p| wanted.iter().all(|w| labels.get(&p.id).is_some_and(|ls| ls.iter().any(|l| l.name.to_lowercase() == *w))))
        .filter(|p| words.iter().all(|w| p.title.to_lowercase().contains(w) || p.body.to_lowercase().contains(w)))
        .collect();
    let sort = q.sort.filter(|s| SORTS.iter().any(|(k, _)| k == s)).unwrap_or_else(|| "updated".into());
    match sort.as_str() {
        "newest" => rows.sort_by_key(|p| std::cmp::Reverse(p.number)),
        "oldest" => rows.sort_by_key(|p| p.number),
        _ => rows.sort_by_key(|p| std::cmp::Reverse(p.updated_ms)),
    }
    let pager = super::Pager::new(rows.len(), q.page, &[("state", &filter), ("q", &qtext), ("sort", &sort)]);
    let rows = pager.slice(rows);
    let bookmarks = app
        .repos
        .read(&repo, |r, _| Ok(r.bookmarks()?.into_iter().map(|b| b.name).collect::<Vec<_>>()))
        .await
        .map_err(|e| Error::from_repo(shell.clone(), e))?;
    Ok(Page(ProposalsPage {
        shell,
        repo: RepoShell::new(&app, &row, "proposals").with_role(role),
        rows,
        filter,
        counts,
        bookmarks,
        q: qtext,
        sort,
        pager,
        labels,
    }))
}

// ------------------------------------------------------------------- new

#[derive(Template)]
#[template(path = "proposal_new.html")]
pub struct NewProposalPage {
    shell: Shell,
    repo: RepoShell,
    bookmarks: Vec<String>,
    source: String,
    target: String,
    error: Option<String>,
    /// Preview: the changes the proposal would add.
    preview: Vec<ChangeView>,
    conflicted: bool,
}

#[derive(Deserialize)]
pub struct NewQuery {
    source: Option<String>,
    target: Option<String>,
}

/// `owner/name:bookmark` for a fork, else a bookmark of this repository.
fn parse_source(app: &Shared, repo: &RepoName, source: &str) -> Option<(Option<RepoName>, String)> {
    if let Some((slug, bookmark)) = source.split_once(':') {
        let fork = RepoName::parse(slug)?;
        if !app.repos.exists(&fork) || fork == *repo {
            return None;
        }
        return Some((Some(fork), bookmark.to_string()));
    }
    crate::repos::names::valid_segment(source).then(|| (None, source.to_string()))
}

async fn preview_for(
    app: &Shared,
    repo: &RepoName,
    target: &str,
    source: &str,
) -> Result<(Vec<ChangeView>, bool), crate::repos::RepoError> {
    let Some((fork, bookmark)) = parse_source(app, repo, source) else { return Ok((vec![], false)) };
    let target = target.to_string();
    let fork_dir = fork.as_ref().map(|f| app.repos.dir(f));
    app.repos
        .read(repo, move |r, cache| {
            let projection = match &fork_dir {
                Some(dir) => {
                    let fork_repo = oxy_core::repo::Repo::open(dir)?;
                    let heads = fork_repo.bookmarks()?.into_iter().find(|b| b.name == bookmark).map(|b| b.heads).unwrap_or_default();
                    pl::project(r, cache, &target, Source::Fork { fork: &fork_repo, heads })?
                }
                None => {
                    let heads = r.bookmarks()?.into_iter().find(|b| b.name == bookmark).map(|b| b.heads).unwrap_or_default();
                    pl::project(r, cache, &target, Source::Bookmark(heads))?
                }
            };
            Ok((projection.changes, projection.conflicted))
        })
        .await
}

pub async fn new_form(
    State(app): State<Shared>,
    viewer: Viewer,
    Path((owner, name)): Path<(String, String)>,
    Query(q): Query<NewQuery>,
) -> Result<Page<NewProposalPage>, Error> {
    let shell = Shell::new(&app, &format!("/{owner}/{name}/proposals/new"), &viewer);
    require(&viewer, &shell)?;
    let (repo, row, role) = lookup(&app, &shell, &viewer, &owner, &name).await?;
    let bookmarks = app
        .repos
        .read(&repo, |r, _| Ok(r.bookmarks()?.into_iter().map(|b| b.name).collect::<Vec<_>>()))
        .await
        .map_err(|e| Error::from_repo(shell.clone(), e))?;
    let target = q.target.unwrap_or_else(|| row.default_bookmark.clone());
    let source = q.source.unwrap_or_default();
    let (preview, conflicted) =
        if source.is_empty() { (vec![], false) } else { preview_for(&app, &repo, &target, &source).await.unwrap_or((vec![], false)) };
    Ok(Page(NewProposalPage {
        shell,
        repo: RepoShell::new(&app, &row, "proposals").with_role(role),
        bookmarks,
        source,
        target,
        error: None,
        preview,
        conflicted,
    }))
}

#[derive(Deserialize)]
pub struct NewForm {
    #[serde(rename = "_csrf")]
    csrf_token: String,
    title: String,
    #[serde(default)]
    body: String,
    target: String,
    source: String,
    #[serde(default)]
    draft: Option<String>,
}

/// Open a proposal from a form or the API: validate, create, index, notify.
#[allow(clippy::too_many_arguments)]
pub async fn open_proposal(
    app: &Shared,
    repo: &RepoName,
    row: &db::repos::RepoRow,
    me: &accounts::Account,
    title: &str,
    body: &str,
    target: &str,
    source: &str,
    draft: bool,
) -> Result<pdb::ProposalRow, String> {
    if title.trim().is_empty() {
        return Err("Give the proposal a title.".into());
    }
    let bookmarks =
        app.repos.read(repo, |r, _| Ok(r.bookmarks()?.into_iter().map(|b| b.name).collect::<Vec<_>>())).await.map_err(|e| e.to_string())?;
    if !bookmarks.iter().any(|b| b == target) {
        return Err("Pick a target bookmark of this repository.".into());
    }
    let Some((fork, bookmark)) = parse_source(app, repo, source.trim()) else {
        return Err("The source is a bookmark of this repository, or owner/name:bookmark of a fork.".into());
    };
    if fork.is_none() && bookmark == target {
        return Err("The source and the target are the same bookmark.".into());
    }
    let (preview, _) = preview_for(app, repo, target, source.trim()).await.map_err(|e| e.to_string())?;
    if preview.is_empty() {
        return Err("The source adds nothing to the target.".into());
    }
    let source_repo_id = match &fork {
        Some(fk) => db::repos::get(&app.db, &fk.owner, &fk.name).await.map_err(|e| e.to_string())?.map(|r| r.id),
        None => None,
    };
    let created = pdb::create(
        &app.db,
        pdb::NewProposal {
            repo_id: row.id,
            title: title.trim(),
            body: body.trim(),
            author_id: Some(me.id),
            author: &me.username,
            draft,
            target,
            source_kind: if fork.is_some() { "fork" } else { "bookmark" },
            source_repo_id,
            source_bookmark: &bookmark,
            source_changes: "",
        },
    )
    .await
    .map_err(|e| e.to_string())?;
    pdb::add_event(&app.db, created.id, &me.username, "opened", "").await.ok();
    accounts::audit(&app.db, Some(me), "proposal.opened", &format!("{}#{}", row.slug(), created.number), title).await.ok();
    db::notify::index(&app.db, "proposal", row.id, created.id, created.number, &created.title, &created.body).await.ok();
    let url = format!("/{}/proposal/{}", row.slug(), created.number);
    crate::notify::deliver(
        app,
        crate::notify::Event {
            kind: "proposal.opened",
            title: format!("{}#{}: {}", row.slug(), created.number, created.title),
            url,
            actor: me,
            repo_id: row.id,
            thread: Some(("proposal", created.id)),
            mention_text: body,
            direct: vec![],
        },
    )
    .await;
    crate::hooks::emit(
        app,
        row,
        "proposal.opened",
        &me.username,
        serde_json::json!({ "number": created.number, "title": created.title, "target": target, "source": source }),
    )
    .await;
    Ok(created)
}

pub async fn create(
    State(app): State<Shared>,
    viewer: Viewer,
    Path((owner, name)): Path<(String, String)>,
    Form(f): Form<NewForm>,
) -> Result<Response, Error> {
    let shell = Shell::new(&app, &format!("/{owner}/{name}/proposals/new"), &viewer);
    let me = require(&viewer, &shell)?;
    csrf(&viewer, &f.csrf_token, &shell)?;
    let (repo, row, role) = lookup(&app, &shell, &viewer, &owner, &name).await?;
    match open_proposal(&app, &repo, &row, &me.account, &f.title, &f.body, &f.target, &f.source, f.draft.is_some()).await {
        Ok(created) => Ok(Redirect::to(&format!("/{owner}/{name}/proposal/{}", created.number)).into_response()),
        Err(msg) => {
            let bookmarks =
                app.repos.read(&repo, |r, _| Ok(r.bookmarks()?.into_iter().map(|b| b.name).collect::<Vec<_>>())).await.unwrap_or_default();
            Ok(Page(NewProposalPage {
                shell,
                repo: RepoShell::new(&app, &row, "proposals").with_role(role),
                bookmarks,
                source: f.source.clone(),
                target: f.target.clone(),
                error: Some(msg),
                preview: vec![],
                conflicted: false,
            })
            .into_response())
        }
    }
}

// ---------------------------------------------------------------- detail

/// A comment placed on a diff row, or general.
pub struct CommentView {
    pub row: pdb::CommentRow,
    pub body_html: String,
    pub line: Option<usize>,
}

pub struct ReviewView {
    pub row: pdb::ReviewRow,
    pub body_html: String,
    pub sealed: bool,
}

/// Everything the detail page and the API need, computed once under the lock.
pub struct Loaded {
    pub row: pdb::ProposalRow,
    pub changes: Vec<ChangeView>,
    pub hashes: Vec<ChangeHash>,
    pub heads: Vec<ChangeHash>,
    pub state: String,
    pub target_state: String,
    pub conflicted: bool,
    pub conflicts: Vec<ConflictView>,
    pub files: Vec<FileRows>,
    /// The per-file hunks and bases behind `files`, to render again with other options.
    pub diffs: Vec<oxy_core::repo::FileDiff>,
    pub bases: std::collections::BTreeMap<String, Vec<u8>>,
    /// Atom per (path, new line number) of the projected state.
    pub atoms: HashMap<(String, usize), (String, u32)>,
    pub sealing_keys: Vec<String>,
    pub touched: Vec<String>,
    pub owners: Vec<String>,
    pub landed_already: bool,
}

/// Compute the projection and everything derived from it.
pub async fn load(app: &Shared, repo: &RepoName, row: pdb::ProposalRow) -> Result<Loaded, crate::repos::RepoError> {
    let fork_dir = match (row.source_kind.as_str(), row.source_repo_id) {
        ("fork", Some(id)) => {
            db::repos::get_by_id(&app.db, id).await.ok().flatten().and_then(|r| RepoName::new(&r.owner, &r.name)).map(|n| app.repos.dir(&n))
        }
        _ => None,
    };
    let r2 = row.clone();
    let loaded = app
        .repos
        .read(repo, move |r, cache| {
            let source = match (r2.source_kind.as_str(), &fork_dir) {
                ("changes", _) => Source::Changes(r2.source_changes().iter().filter_map(|h| ChangeHash::from_hex(h)).collect()),
                ("fork", Some(dir)) => {
                    let fork_repo = oxy_core::repo::Repo::open(dir)?;
                    let heads =
                        fork_repo.bookmarks()?.into_iter().find(|b| b.name == r2.source_bookmark).map(|b| b.heads).unwrap_or_default();
                    // Bring the fork's changes over now, so the projection below can read them.
                    let fork_state = fork_repo.load_state(&heads)?;
                    let missing: Vec<ChangeHash> = fork_state.changes().map(|(h, _)| *h).filter(|h| !r.store().has(h)).collect();
                    if !missing.is_empty() {
                        r.import_bundle(&fork_repo.bundle_for(&missing)?, r.current_policy()?.is_some())?;
                    }
                    Source::Changes(heads)
                }
                _ => {
                    let heads = r.bookmarks()?.into_iter().find(|b| b.name == r2.source_bookmark).map(|b| b.heads).unwrap_or_default();
                    Source::Bookmark(heads)
                }
            };
            let p: Projection = pl::project(r, cache, &r2.target, source)?;
            let target_loaded = cache.load(r, &p.target_heads)?;
            let files = render_files(&p.files, &p.bases);
            let mut atoms = HashMap::new();
            for f in &files {
                for l in &f.lines {
                    if let Some(n) = l.new_no {
                        if let Some((h, i)) = pl::atom_at(&p.loaded, &f.path, n as usize) {
                            atoms.insert((f.path.clone(), n as usize), (h.to_hex(), i));
                        }
                    }
                }
            }
            let touched: Vec<String> = p.files.iter().map(|f| f.path.clone()).collect();
            let owners = pl::owners_for(&target_loaded, &touched);
            let sealing = pl::sealing_keys(r, &p.hashes)?.into_iter().map(|k| k.to_hex()).collect();
            let landed_already = !p.hashes.is_empty() && p.hashes.iter().all(|h| target_loaded.state.contains(h));
            Ok(Loaded {
                row: r2,
                changes: p.changes,
                hashes: p.hashes,
                heads: p.heads,
                state: p.state.to_hex(),
                target_state: p.target_state.to_hex(),
                conflicted: p.conflicted,
                conflicts: p.conflicts,
                files,
                diffs: p.files.clone(),
                bases: p.bases.clone(),
                atoms,
                sealing_keys: sealing,
                touched,
                owners,
                landed_already,
            })
        })
        .await?;
    // Remember the projection for the list, the API and other proposals' stacking checks.
    let heads_csv = loaded.heads.iter().map(|h| h.to_hex()).collect::<Vec<_>>().join(",");
    let changes_csv = loaded.hashes.iter().map(|h| h.to_hex()).collect::<Vec<_>>().join(",");
    pdb::set_projection(&app.db, loaded.row.id, &loaded.state, &heads_csv, &loaded.target_state, &changes_csv, loaded.conflicted)
        .await
        .ok();
    Ok(loaded)
}

/// Reviews, approvals and blockers.
pub struct Verdict {
    pub reviews: Vec<ReviewView>,
    pub approvals: Vec<Approval>,
    pub blockers: Vec<String>,
    pub depends_on: Vec<i64>,
    pub requirements: pdb::Requirements,
}

pub async fn verdict(app: &Shared, loaded: &Loaded, repo_id: i64) -> Result<Verdict, sqlx::Error> {
    let rows = pdb::reviews(&app.db, loaded.row.id).await?;
    let links = accounts::identity_accounts(&app.db).await?;
    let sealed_accounts: Vec<String> = links.iter().filter(|(k, _)| loaded.sealing_keys.contains(k)).map(|(_, u)| u.clone()).collect();
    // Latest verdict per reviewer.
    let mut latest: BTreeMap<String, &pdb::ReviewRow> = BTreeMap::new();
    for r in &rows {
        latest.insert(r.author.clone(), r);
    }
    let mut approvals = Vec::new();
    for (who, r) in &latest {
        if r.verdict == "approve" {
            let sealed = sealed_accounts.contains(who);
            let key = links.iter().find(|(k, u)| u == who && loaded.sealing_keys.contains(k)).map(|(k, _)| k.clone());
            approvals.push(Approval { account: who.clone(), sealed, key });
        }
    }
    let reviews = rows
        .iter()
        .map(|r| ReviewView {
            row: r.clone(),
            body_html: render::markdown::render(&r.body, "/", "/"),
            sealed: r.verdict == "approve" && sealed_accounts.contains(&r.author),
        })
        .collect();
    let requirements = pdb::requirements(&app.db, repo_id).await?;
    let mut blockers = Vec::new();
    if loaded.row.state == "draft" {
        blockers.push("the proposal is a draft".into());
    }
    if loaded.hashes.is_empty() {
        blockers.push("the proposal adds no changes".into());
    }
    let sealed_count = approvals.iter().filter(|a| a.sealed).count() as i64;
    if sealed_count < requirements.required_approvals {
        blockers.push(format!("{sealed_count} of {} required sealed approvals", requirements.required_approvals));
    }
    if requirements.require_owners {
        let missing: Vec<&String> = loaded.owners.iter().filter(|o| !approvals.iter().any(|a| a.sealed && &a.account == *o)).collect();
        if !missing.is_empty() {
            blockers.push(format!("code owners still to approve: {}", missing.iter().map(|s| s.as_str()).collect::<Vec<_>>().join(", ")));
        }
    }
    if loaded.conflicted && !requirements.allow_conflicts {
        blockers.push("landing would carry conflicts, which this repository refuses".into());
    }
    let required = db::hooks::required_checks(&app.db, repo_id).await?;
    if !required.is_empty() {
        let checks = db::hooks::checks_for_state(&app.db, repo_id, &loaded.state).await?;
        let missing: Vec<String> =
            required.iter().filter(|n| !checks.iter().any(|c| &c.name == *n && c.status == "passed")).cloned().collect();
        if !missing.is_empty() {
            blockers.push(format!("required checks not passed on the projected state: {}", missing.join(", ")));
        }
    }
    let requesting: Vec<&String> = latest.iter().filter(|(_, r)| r.verdict == "changes").map(|(who, _)| who).collect();
    if !requesting.is_empty() {
        blockers.push(format!("changes requested by {}", requesting.iter().map(|s| s.as_str()).collect::<Vec<_>>().join(", ")));
    }
    // Stacking: another open, earlier proposal whose changes this one includes.
    let mut depends_on = Vec::new();
    for other in pdb::list(&app.db, repo_id, &["open", "draft"]).await? {
        if other.id == loaded.row.id || other.number > loaded.row.number {
            continue;
        }
        let theirs = other.projected_changes();
        if !theirs.is_empty() && theirs.iter().all(|h| loaded.hashes.iter().any(|m| m.to_hex() == *h)) {
            depends_on.push(other.number);
        }
    }
    if !depends_on.is_empty() {
        blockers.push(format!("depends on {}", depends_on.iter().map(|n| format!("#{n}")).collect::<Vec<_>>().join(", ")));
    }
    Ok(Verdict { reviews, approvals, blockers, depends_on, requirements })
}

#[derive(Template)]
#[template(path = "proposal.html")]
pub struct ProposalPage {
    shell: Shell,
    repo: RepoShell,
    p: pdb::ProposalRow,
    body_html: String,
    tab: String,
    changes: Vec<ChangeView>,
    files: Vec<FileRows>,
    diffs: Vec<oxy_core::repo::FileDiff>,
    bases: std::collections::BTreeMap<String, Vec<u8>>,
    /// Whitespace-only changes are hidden (`?w=1`).
    ignore_ws: bool,
    conflicts: Vec<ConflictView>,
    conflicted: bool,
    comments: Vec<CommentView>,
    /// Anchored comments by (path, current line).
    placed: HashMap<(String, usize), Vec<usize>>,
    outdated: Vec<usize>,
    reviews: Vec<ReviewView>,
    approvals: Vec<Approval>,
    blockers: Vec<String>,
    depends_on: Vec<i64>,
    events: Vec<pdb::EventRow>,
    owners: Vec<String>,
    requirements: pdb::Requirements,
    landed_already: bool,
    can_edit: bool,
    can_land: bool,
    hub_can_land: bool,
    notice: Option<String>,
    error: Option<String>,
    heads: Vec<String>,
    state_hash: String,
    source_label: String,
    api_url: String,
    labels: Vec<db::issues::Label>,
    all_labels: Vec<db::issues::Label>,
    checks: Vec<db::hooks::Check>,
    required_checks: Vec<String>,
}

#[derive(Deserialize)]
pub struct DetailQuery {
    tab: Option<String>,
    #[serde(default)]
    w: Option<String>,
}

/// The page assembler every action ends in; its arguments are the route
/// plus what to say, and a struct would only rename them.
#[allow(clippy::too_many_arguments)]
async fn detail(
    app: &Shared,
    shell: Shell,
    viewer: &Viewer,
    owner: &str,
    name: &str,
    number: i64,
    tab: String,
    notice: Option<String>,
    error: Option<String>,
) -> Result<Page<ProposalPage>, Error> {
    let (repo, row, role) = lookup(app, &shell, viewer, owner, name).await?;
    let p = pdb::get(&app.db, row.id, number)
        .await
        .map_err(|e| Error::from_db(shell.clone(), e))?
        .ok_or_else(|| Error::not_found(shell.clone()))?;
    let loaded = load(app, &repo, p).await.map_err(|e| Error::from_repo(shell.clone(), e))?;
    // A proposal whose changes all reached the target landed by another route.
    if loaded.landed_already && loaded.row.is_open() {
        pdb::set_state(&app.db, loaded.row.id, "landed", &loaded.target_state).await.ok();
        pdb::add_event(&app.db, loaded.row.id, "", "landed", "every change reached the target").await.ok();
    }
    let p = pdb::get(&app.db, row.id, number).await.map_err(|e| Error::from_db(shell.clone(), e))?.unwrap_or(loaded.row.clone());
    let v = verdict(app, &loaded, row.id).await.map_err(|e| Error::from_db(shell.clone(), e))?;
    let comment_rows = pdb::comments(&app.db, loaded.row.id).await.map_err(|e| Error::from_db(shell.clone(), e))?;
    let events = pdb::events(&app.db, loaded.row.id).await.map_err(|e| Error::from_db(shell.clone(), e))?;
    // Place anchored comments at their atom's current line.
    let mut by_atom: HashMap<(String, String, u32), usize> = HashMap::new();
    for ((path, line), (h, i)) in &loaded.atoms {
        by_atom.insert((path.clone(), h.clone(), *i), *line);
    }
    let mut comments = Vec::new();
    let mut placed: HashMap<(String, usize), Vec<usize>> = HashMap::new();
    let mut outdated = Vec::new();
    for (idx, c) in comment_rows.into_iter().enumerate() {
        let line = if c.anchor_change.is_empty() {
            None
        } else {
            by_atom.get(&(c.path.clone(), c.anchor_change.clone(), c.anchor_index as u32)).copied()
        };
        if !c.anchor_change.is_empty() {
            match line {
                Some(l) => placed.entry((c.path.clone(), l)).or_default().push(idx),
                None => outdated.push(idx),
            }
        }
        comments.push(CommentView { body_html: render::markdown::render(&c.body, "/", "/"), row: c, line });
    }
    let mut changes = loaded.changes.clone();
    super::attribute(app, &mut changes.iter_mut().collect::<Vec<_>>()).await;
    let me = viewer.account();
    let can_edit = me.is_some_and(|a| Some(a.id) == p.author_id || role >= Role::Maintain);
    let can_land = role >= Role::Write && p.is_open() && v.blockers.is_empty();
    let delegated = match viewer.account() {
        Some(a) => super::edit::delegated_identity(app, a.id).await.is_some(),
        None => false,
    };
    let hub_can_land = delegated || app.repos.read(&repo, |r, _| Ok(r.current_policy()?.is_none())).await.unwrap_or(false);
    let source_label = match p.source_kind.as_str() {
        "fork" => format!(
            "fork {}",
            db::repos::get_by_id(&app.db, p.source_repo_id.unwrap_or(0))
                .await
                .ok()
                .flatten()
                .map(|r| format!("{}:{}", r.slug(), p.source_bookmark))
                .unwrap_or_default()
        ),
        "changes" => format!("{} changes", p.source_changes().len()),
        _ => p.source_bookmark.clone(),
    };
    Ok(Page(ProposalPage {
        shell,
        repo: RepoShell::new(app, &row, "proposals").with_role(role),
        body_html: super::issues::markdown(app, row.id, &format!("/{owner}/{name}"), &p.body).await,
        p,
        tab,
        changes,
        files: loaded.files,
        diffs: loaded.diffs,
        bases: loaded.bases,
        ignore_ws: false,
        conflicts: loaded.conflicts,
        conflicted: loaded.conflicted,
        comments,
        placed,
        outdated,
        reviews: v.reviews,
        approvals: v.approvals,
        blockers: v.blockers,
        depends_on: v.depends_on,
        events,
        owners: loaded.owners,
        requirements: v.requirements,
        landed_already: loaded.landed_already,
        can_edit,
        can_land,
        hub_can_land,
        notice,
        error,
        heads: loaded.heads.iter().map(|h| h.to_hex()).collect(),
        state_hash: loaded.state.clone(),
        source_label,
        api_url: format!("{}/api/v1/repos/{owner}/{name}/proposals/{number}", app.config.base_url()),
        labels: db::issues::proposal_labels(&app.db, loaded.row.id).await.unwrap_or_default(),
        all_labels: db::issues::labels(&app.db, row.id).await.unwrap_or_default(),
        checks: db::hooks::checks_for_state(&app.db, row.id, &loaded.state).await.unwrap_or_default(),
        required_checks: db::hooks::required_checks(&app.db, row.id).await.unwrap_or_default(),
    }))
}

pub async fn show(
    State(app): State<Shared>,
    viewer: Viewer,
    Path((owner, name, number)): Path<(String, String, i64)>,
    Query(q): Query<DetailQuery>,
) -> Result<Page<ProposalPage>, Error> {
    let shell = Shell::new(&app, &format!("/{owner}/{name}/proposal/{number}"), &viewer);
    let mut page = detail(&app, shell, &viewer, &owner, &name, number, q.tab.unwrap_or_else(|| "conversation".into()), None, None).await?;
    if q.w.as_deref() == Some("1") {
        // Hide whitespace-only changes: the same hunks, rendered again.
        page.0.files =
            super::history::render_files_with(&page.0.diffs, &page.0.bases, crate::render::diff::Options { ignore_whitespace: true });
        page.0.ignore_ws = true;
    }
    Ok(page)
}

// ---------------------------------------------------------------- actions

#[derive(Deserialize)]
pub struct CommentForm {
    #[serde(rename = "_csrf")]
    csrf_token: String,
    body: String,
    #[serde(default)]
    path: String,
    #[serde(default)]
    line: Option<usize>,
}

pub async fn comment(
    State(app): State<Shared>,
    viewer: Viewer,
    Path((owner, name, number)): Path<(String, String, i64)>,
    Form(f): Form<CommentForm>,
) -> Result<Page<ProposalPage>, Error> {
    let shell = Shell::new(&app, &format!("/{owner}/{name}/proposal/{number}"), &viewer);
    let me = require(&viewer, &shell)?;
    csrf(&viewer, &f.csrf_token, &shell)?;
    let (repo, row, _) = lookup(&app, &shell, &viewer, &owner, &name).await?;
    let p = pdb::get(&app.db, row.id, number)
        .await
        .map_err(|e| Error::from_db(shell.clone(), e))?
        .ok_or_else(|| Error::not_found(shell.clone()))?;
    if f.body.trim().is_empty() {
        return detail(
            &app,
            shell,
            &viewer,
            &owner,
            &name,
            number,
            "conversation".into(),
            None,
            Some("An empty comment says nothing.".into()),
        )
        .await;
    }
    let anchor = match (f.path.trim(), f.line) {
        ("", _) | (_, None) => None,
        (path, Some(line)) => {
            let loaded = load(&app, &repo, p.clone()).await.map_err(|e| Error::from_repo(shell.clone(), e))?;
            loaded.atoms.get(&(path.to_string(), line)).cloned()
        }
    };
    let tab = if anchor.is_some() { "files" } else { "conversation" };
    pdb::add_comment(
        &app.db,
        p.id,
        Some(me.account.id),
        &me.account.username,
        f.body.trim(),
        f.path.trim(),
        anchor.as_ref().map(|(h, i)| (h.as_str(), *i as i64)),
    )
    .await
    .map_err(|e| Error::from_db(shell.clone(), e))?;
    detail(&app, shell, &viewer, &owner, &name, number, tab.into(), None, None).await
}

#[derive(Deserialize)]
pub struct ReviewForm {
    #[serde(rename = "_csrf")]
    csrf_token: String,
    verdict: String,
    #[serde(default)]
    body: String,
}

pub async fn review(
    State(app): State<Shared>,
    viewer: Viewer,
    Path((owner, name, number)): Path<(String, String, i64)>,
    Form(f): Form<ReviewForm>,
) -> Result<Page<ProposalPage>, Error> {
    let shell = Shell::new(&app, &format!("/{owner}/{name}/proposal/{number}"), &viewer);
    let me = require(&viewer, &shell)?;
    csrf(&viewer, &f.csrf_token, &shell)?;
    let (_, row, _) = lookup(&app, &shell, &viewer, &owner, &name).await?;
    let p = pdb::get(&app.db, row.id, number)
        .await
        .map_err(|e| Error::from_db(shell.clone(), e))?
        .ok_or_else(|| Error::not_found(shell.clone()))?;
    if !matches!(f.verdict.as_str(), "comment" | "changes" | "approve") {
        return Err(Error::bad(shell, "a review is comment, changes or approve"));
    }
    if f.verdict == "approve" && Some(me.account.id) == p.author_id {
        return detail(
            &app,
            shell,
            &viewer,
            &owner,
            &name,
            number,
            "conversation".into(),
            None,
            Some("You cannot approve your own proposal.".into()),
        )
        .await;
    }
    pdb::add_review(&app.db, p.id, me.account.id, &me.account.username, &f.verdict, f.body.trim())
        .await
        .map_err(|e| Error::from_db(shell.clone(), e))?;
    pdb::add_event(&app.db, p.id, &me.account.username, &format!("review.{}", f.verdict), "").await.ok();
    crate::hooks::emit(&app, &row, "review", &me.account.username, serde_json::json!({ "number": number, "verdict": f.verdict })).await;
    let notice = if f.verdict == "approve" {
        Some(format!(
            "Approval recorded. It counts once you seal the changes: oxy seal --proposal {}/{owner}/{name}/proposal/{number}",
            app.config.base_url()
        ))
    } else {
        None
    };
    detail(&app, shell, &viewer, &owner, &name, number, "conversation".into(), notice, None).await
}

#[derive(Deserialize)]
pub struct EditForm {
    #[serde(rename = "_csrf")]
    csrf_token: String,
    title: String,
    #[serde(default)]
    body: String,
    target: String,
}

pub async fn edit(
    State(app): State<Shared>,
    viewer: Viewer,
    Path((owner, name, number)): Path<(String, String, i64)>,
    Form(f): Form<EditForm>,
) -> Result<Page<ProposalPage>, Error> {
    let shell = Shell::new(&app, &format!("/{owner}/{name}/proposal/{number}"), &viewer);
    let me = require(&viewer, &shell)?;
    csrf(&viewer, &f.csrf_token, &shell)?;
    let (_, row, role) = lookup(&app, &shell, &viewer, &owner, &name).await?;
    let p = pdb::get(&app.db, row.id, number)
        .await
        .map_err(|e| Error::from_db(shell.clone(), e))?
        .ok_or_else(|| Error::not_found(shell.clone()))?;
    if Some(me.account.id) != p.author_id && role < Role::Maintain {
        return Err(Error::not_found(shell));
    }
    let target = if crate::repos::names::valid_segment(f.target.trim()) { f.target.trim() } else { &p.target };
    pdb::edit(&app.db, p.id, f.title.trim(), f.body.trim(), target).await.map_err(|e| Error::from_db(shell.clone(), e))?;
    pdb::add_event(&app.db, p.id, &me.account.username, "edited", "").await.ok();
    detail(&app, shell, &viewer, &owner, &name, number, "conversation".into(), Some("Saved.".into()), None).await
}

#[derive(Deserialize)]
pub struct StateForm {
    #[serde(rename = "_csrf")]
    csrf_token: String,
    action: String,
}

pub async fn state(
    State(app): State<Shared>,
    viewer: Viewer,
    Path((owner, name, number)): Path<(String, String, i64)>,
    Form(f): Form<StateForm>,
) -> Result<Page<ProposalPage>, Error> {
    let shell = Shell::new(&app, &format!("/{owner}/{name}/proposal/{number}"), &viewer);
    let me = require(&viewer, &shell)?;
    csrf(&viewer, &f.csrf_token, &shell)?;
    let (_, row, role) = lookup(&app, &shell, &viewer, &owner, &name).await?;
    let p = pdb::get(&app.db, row.id, number)
        .await
        .map_err(|e| Error::from_db(shell.clone(), e))?
        .ok_or_else(|| Error::not_found(shell.clone()))?;
    if Some(me.account.id) != p.author_id && role < Role::Triage {
        return Err(Error::not_found(shell));
    }
    let new_state = match (f.action.as_str(), p.state.as_str()) {
        ("close", "open" | "draft") => "closed",
        ("reopen", "closed") => "open",
        ("ready", "draft") => "open",
        ("draft", "open") => "draft",
        _ => return Err(Error::bad(shell, "that transition is not possible")),
    };
    pdb::set_state(&app.db, p.id, new_state, "").await.map_err(|e| Error::from_db(shell.clone(), e))?;
    pdb::add_event(&app.db, p.id, &me.account.username, new_state, "").await.ok();
    crate::hooks::emit(&app, &row, &format!("proposal.{new_state}"), &me.account.username, serde_json::json!({ "number": number })).await;
    detail(&app, shell, &viewer, &owner, &name, number, "conversation".into(), None, None).await
}

pub async fn resolve_comment(
    State(app): State<Shared>,
    viewer: Viewer,
    Path((owner, name, number, id)): Path<(String, String, i64, i64)>,
    Form(f): Form<super::session::CsrfForm>,
) -> Result<Page<ProposalPage>, Error> {
    let shell = Shell::new(&app, &format!("/{owner}/{name}/proposal/{number}"), &viewer);
    require(&viewer, &shell)?;
    csrf(&viewer, &f.csrf, &shell)?;
    let (_, row, _) = lookup(&app, &shell, &viewer, &owner, &name).await?;
    let p = pdb::get(&app.db, row.id, number)
        .await
        .map_err(|e| Error::from_db(shell.clone(), e))?
        .ok_or_else(|| Error::not_found(shell.clone()))?;
    let current: Option<bool> = sqlx::query_scalar("SELECT resolved FROM proposal_comments WHERE id = ? AND proposal_id = ?")
        .bind(id)
        .bind(p.id)
        .fetch_optional(&app.db)
        .await
        .map_err(|e| Error::from_db(shell.clone(), e))?;
    if let Some(r) = current {
        pdb::set_comment_resolved(&app.db, id, !r).await.map_err(|e| Error::from_db(shell.clone(), e))?;
    }
    detail(&app, shell, &viewer, &owner, &name, number, "files".into(), None, None).await
}

/// Land from the hub: only when the repository has no trust policy (the
/// hub never signs a reference update the policy would have to admit).
pub async fn land(
    State(app): State<Shared>,
    viewer: Viewer,
    Path((owner, name, number)): Path<(String, String, i64)>,
    Form(f): Form<super::session::CsrfForm>,
) -> Result<Page<ProposalPage>, Error> {
    let shell = Shell::new(&app, &format!("/{owner}/{name}/proposal/{number}"), &viewer);
    let me = require(&viewer, &shell)?;
    csrf(&viewer, &f.csrf, &shell)?;
    let (repo, row, _) = lookup_role(&app, &shell, &viewer, &owner, &name, Access::Write).await?;
    let p = pdb::get(&app.db, row.id, number)
        .await
        .map_err(|e| Error::from_db(shell.clone(), e))?
        .ok_or_else(|| Error::not_found(shell.clone()))?;
    let loaded = load(&app, &repo, p.clone()).await.map_err(|e| Error::from_repo(shell.clone(), e))?;
    let v = verdict(&app, &loaded, row.id).await.map_err(|e| Error::from_db(shell.clone(), e))?;
    if !p.is_open() || !v.blockers.is_empty() {
        return detail(
            &app,
            shell,
            &viewer,
            &owner,
            &name,
            number,
            "conversation".into(),
            None,
            Some(format!("Cannot land: {}", v.blockers.join("; "))),
        )
        .await;
    }
    let target = p.target.clone();
    let heads = loaded.heads.clone();
    // With a delegation the landing is attested by the hub key on the
    // user's behalf, which a policy accepts when it lets the user update
    // the target (spec §14.5); without one, only a policy-free repository
    // can be landed here.
    let result = match super::edit::signer_for(&app, me.account.id).await {
        Ok(signer) => crate::repos::edits::move_bookmark(&app.repos, &repo, target.clone(), heads.clone(), signer).await.map(|_| pl::state_ref(&heads).to_hex()),
        Err(why) => {
            app.repos
                .write(&repo, move |r, _| {
                    if r.current_policy()?.is_some() {
                        return Err(crate::repos::RepoError::Oxy(oxy_core::repo::RepoError::Msg(format!(
                            "this repository has a trust policy, so the landing must be signed by a key it authorises. Land from a client with oxy proposal land, or delegate to the hub. {why}"
                        ))));
                    }
                    r.bookmark_set(&target, &heads)?;
                    Ok(pl::state_ref(&heads).to_hex())
                })
                .await
        }
    };
    match result {
        Ok(state) => {
            pdb::set_state(&app.db, p.id, "landed", &state).await.map_err(|e| Error::from_db(shell.clone(), e))?;
            pdb::add_event(&app.db, p.id, &me.account.username, "landed", "from the hub").await.ok();
            crate::hooks::emit(
                &app,
                &row,
                "proposal.landed",
                &me.account.username,
                serde_json::json!({ "number": number, "target": p.target, "state": state }),
            )
            .await;
            crate::notify::deliver(
                &app,
                crate::notify::Event {
                    kind: "proposal.landed",
                    title: format!("{owner}/{name}#{number}: {} landed", p.title),
                    url: format!("/{owner}/{name}/proposal/{number}"),
                    actor: &me.account,
                    repo_id: row.id,
                    thread: Some(("proposal", p.id)),
                    mention_text: "",
                    direct: p.author_id.into_iter().collect(),
                },
            )
            .await;
            if p.target == row.default_bookmark {
                let messages: Vec<(String, String)> =
                    loaded.changes.iter().map(|c| (c.hash.clone(), format!("{}\n{}", c.title, c.body))).collect();
                super::issues::close_from_messages(&app, &row, &messages).await;
            }
            accounts::audit(&app.db, Some(&me.account), "proposal.landed", &format!("{owner}/{name}#{number}"), "").await.ok();
            db::repos::record_push(
                &app.db,
                row.id,
                Some((me.account.id, me.account.username.as_str())),
                &[db::repos::PushOutcome {
                    reference: p.target.clone(),
                    ok: true,
                    reason: format!("landed #{number}"),
                    old_state: loaded.target_state.clone(),
                    new_state: state,
                    heads: loaded.heads.len() as i64,
                    changes: loaded.hashes.len() as i64,
                }],
            )
            .await
            .ok();
            detail(&app, shell, &viewer, &owner, &name, number, "conversation".into(), Some("Landed.".into()), None).await
        }
        Err(e) => detail(&app, shell, &viewer, &owner, &name, number, "conversation".into(), None, Some(e.to_string())).await,
    }
}

#[derive(Deserialize)]
pub struct LabelsForm {
    #[serde(rename = "_csrf")]
    csrf_token: String,
    #[serde(default)]
    label: Vec<i64>,
}

pub async fn set_labels(
    State(app): State<Shared>,
    viewer: Viewer,
    Path((owner, name, number)): Path<(String, String, i64)>,
    axum_extra::extract::Form(f): axum_extra::extract::Form<LabelsForm>,
) -> Result<Page<ProposalPage>, Error> {
    let shell = Shell::new(&app, &format!("/{owner}/{name}/proposal/{number}"), &viewer);
    require(&viewer, &shell)?;
    csrf(&viewer, &f.csrf_token, &shell)?;
    let (_, row, role) = lookup(&app, &shell, &viewer, &owner, &name).await?;
    if role < Role::Triage {
        return Err(Error::not_found(shell));
    }
    let p = pdb::get(&app.db, row.id, number)
        .await
        .map_err(|e| Error::from_db(shell.clone(), e))?
        .ok_or_else(|| Error::not_found(shell.clone()))?;
    for l in db::issues::labels(&app.db, row.id).await.map_err(|e| Error::from_db(shell.clone(), e))? {
        db::issues::set_proposal_label(&app.db, p.id, l.id, f.label.contains(&l.id)).await.map_err(|e| Error::from_db(shell.clone(), e))?;
    }
    detail(&app, shell, &viewer, &owner, &name, number, "conversation".into(), None, None).await
}

/// `GET /{owner}/{name}/proposal/{number}/events`: server-sent events for
/// checks on the projected state (hub spec §13.1).
pub async fn events(
    State(app): State<Shared>,
    viewer: Viewer,
    Path((owner, name, number)): Path<(String, String, i64)>,
) -> Result<axum::response::Sse<impl futures::Stream<Item = Result<axum::response::sse::Event, std::convert::Infallible>>>, Error> {
    use futures::StreamExt;
    let shell = Shell::new(&app, &format!("/{owner}/{name}/proposal/{number}"), &viewer);
    let (_, row, _) = lookup(&app, &shell, &viewer, &owner, &name).await?;
    let rx = app.events.proposals.subscribe();
    let repo_id = row.id;
    let stream = tokio_stream::wrappers::BroadcastStream::new(rx).filter_map(move |item| async move {
        match item {
            Ok((id, ev)) if id == repo_id => {
                Some(Ok(axum::response::sse::Event::default().event(ev.kind.clone()).data(serde_json::to_string(&ev).unwrap_or_default())))
            }
            _ => None,
        }
    });
    Ok(axum::response::Sse::new(stream).keep_alive(axum::response::sse::KeepAlive::default()))
}

// -------------------------------------------------------------------- API

pub async fn to_api(app: &Shared, owner: &str, name: &str, loaded: &Loaded, v: &Verdict, source_url: Option<String>) -> hub_api::Proposal {
    let p = &loaded.row;
    hub_api::Proposal {
        number: p.number,
        title: p.title.clone(),
        body: p.body.clone(),
        author: p.author.clone(),
        state: ProposalState::parse(&p.state).unwrap_or(ProposalState::Open),
        target: p.target.clone(),
        source: match p.source_kind.as_str() {
            "fork" => {
                let (o, n) = source_url
                    .as_deref()
                    .and_then(|u| u.rsplit_once('/'))
                    .and_then(|(b, n)| b.rsplit_once('/').map(|(_, o)| (o.to_string(), n.to_string())))
                    .unwrap_or_default();
                ProposalSource::Fork { owner: o, name: n, bookmark: p.source_bookmark.clone() }
            }
            "changes" => ProposalSource::Changes { hashes: p.source_changes() },
            _ => ProposalSource::Bookmark { bookmark: p.source_bookmark.clone() },
        },
        changes: loaded
            .changes
            .iter()
            .map(|c| hub_api::ChangeSummary {
                hash: c.hash.clone(),
                message: if c.body.is_empty() { c.title.clone() } else { format!("{}\n\n{}", c.title, c.body) },
                author: hub_api::Author {
                    name: c.author.name.clone(),
                    email: c.author.email.clone(),
                    key: c.author.key.clone(),
                    account: c.author.account.clone(),
                },
                when_ms: c.when_ms,
                deps: c.deps.clone(),
                head: c.head,
                signature: match &c.signature {
                    view::SigView::Unsigned => hub_api::Signature::Unsigned,
                    view::SigView::Valid { key, sealed, revoked, .. } => {
                        hub_api::Signature::Valid { key: key.clone(), sealed: *sealed, revoked: *revoked }
                    }
                    view::SigView::Invalid(why) => hub_api::Signature::Invalid { reason: why.clone() },
                },
            })
            .collect(),
        projected_heads: loaded.heads.iter().map(|h| h.to_hex()).collect(),
        projected_state: Some(loaded.state.clone()),
        conflicted: loaded.conflicted,
        approvals: v.approvals.clone(),
        landable: p.is_open() && v.blockers.is_empty(),
        blockers: v.blockers.clone(),
        created_ms: p.created_ms,
        updated_ms: p.updated_ms,
        url: format!("{}/{owner}/{name}/proposal/{}", app.config.base_url(), p.number),
        repository_url: format!("{}/{owner}/{name}", app.config.base_url()),
        source_url,
    }
}

/// The line comment form's placement key, for templates.
pub fn key(path: &str, line: impl filters::Num) -> (String, usize) {
    (path.to_string(), line.as_u64() as usize)
}

#[allow(dead_code)]
fn _unused(_: &diff::Line, _: &ConflictView, _: &Role) {}