//! History, change and compare pages.

use super::{filters, lookup, Error, Page, RepoShell, Shell};
use crate::auth::Viewer;
use crate::render::{self, diff, graph};
use crate::repos::view;
use crate::Shared;
use askama::Template;
use axum::extract::{Path, Query, State};
use oxy_core::repo::FileDiff;
use serde::Deserialize;
use std::collections::BTreeMap;

const PAGE: usize = 50;

#[derive(Deserialize)]
pub struct HistoryQuery {
    path: Option<String>,
    offset: Option<usize>,
}

#[derive(Template)]
#[template(path = "history.html")]
pub struct HistoryPage {
    shell: Shell,
    repo: RepoShell,
    h: view::History,
    rows: Vec<graph::Row>,
    lanes: usize,
}

pub async fn history(
    State(app): State<Shared>,
    viewer: Viewer,
    Path((owner, name, r)): Path<(String, String, String)>,
    Query(q): Query<HistoryQuery>,
) -> Result<Page<HistoryPage>, Error> {
    let shell = Shell::new(&app, &format!("/{owner}/{name}/changes/{r}"), &viewer);
    let (repo, row, role) = lookup(&app, &shell, &viewer, &owner, &name).await?;
    let spec = r.clone();
    let path = q.path.clone().filter(|p| !p.is_empty());
    let offset = q.offset.unwrap_or(0);
    let h = app
        .repos
        .read(&repo, move |repo, cache| {
            let target = view::resolve(repo, cache, &spec)?;
            view::history(repo, cache, target, path.as_deref(), offset, PAGE)
        })
        .await
        .map_err(|e| Error::from_repo(shell.clone(), e))?;
    let mut h = h;
    super::attribute(&app, &mut h.entries.iter_mut().collect::<Vec<_>>()).await;
    let graph_input: Vec<(String, Vec<String>)> = h.entries.iter().map(|c| (c.hash.clone(), c.deps.clone())).collect();
    let rows = graph::layout(&graph_input);
    let lanes = graph::width(&rows);
    Ok(Page(HistoryPage { shell, repo: RepoShell::new(&app, &row, "changes").with_role(role), h, rows, lanes }))
}

/// A file's diff, rendered.
pub struct FileRows {
    pub path: String,
    pub from: Option<String>,
    pub kind: String,
    pub lines: Vec<diff::Line>,
    pub added: usize,
    pub removed: usize,
    pub anchor: String,
}

pub fn render_files(files: &[FileDiff], bases: &BTreeMap<String, Vec<u8>>) -> Vec<FileRows> {
    render_files_with(files, bases, diff::Options::default())
}

/// `render_files` with diff options (hub spec §6.4: `?w=1` hides whitespace changes).
pub fn render_files_with(files: &[FileDiff], bases: &BTreeMap<String, Vec<u8>>, opts: diff::Options) -> Vec<FileRows> {
    files
        .iter()
        .enumerate()
        .map(|(i, f)| {
            let base = bases.get(&f.path).map(Vec::as_slice).unwrap_or(b"");
            let lines = diff::unified_with(base, &f.hunks, 3, opts);
            FileRows {
                path: f.path.clone(),
                from: f.from.clone(),
                kind: f.kind.clone(),
                added: lines.iter().filter(|l| l.kind == diff::Kind::Add).count(),
                removed: lines.iter().filter(|l| l.kind == diff::Kind::Del).count(),
                lines,
                anchor: format!("diff-{i}"),
            }
        })
        .collect()
}

#[derive(Template)]
#[template(path = "change.html")]
pub struct ChangePage {
    shell: Shell,
    repo: RepoShell,
    c: view::ChangeDetail,
    files: Vec<FileRows>,
    body_html: String,
    ignore_ws: bool,
}

/// `?w=1` on a diff page hides whitespace-only changes.
#[derive(Deserialize, Default)]
pub struct DiffQuery {
    #[serde(default)]
    w: Option<String>,
}

impl DiffQuery {
    pub fn options(&self) -> diff::Options {
        diff::Options { ignore_whitespace: self.w.as_deref() == Some("1") }
    }
}

pub async fn change(
    State(app): State<Shared>,
    viewer: Viewer,
    Path((owner, name, hash)): Path<(String, String, String)>,
    Query(q): Query<DiffQuery>,
) -> Result<Page<ChangePage>, Error> {
    let shell = Shell::new(&app, &format!("/{owner}/{name}/change/{hash}"), &viewer);
    let (repo, row, role) = lookup(&app, &shell, &viewer, &owner, &name).await?;
    let spec = hash.clone();
    let c = app
        .repos
        .read(&repo, move |repo, cache| {
            let h = view::resolve_change(repo, cache, &spec)?;
            view::change(repo, cache, &h)
        })
        .await
        .map_err(|e| Error::from_repo(shell.clone(), e))?;
    let mut c = c;
    {
        let mut all: Vec<&mut view::ChangeView> = vec![&mut c.view];
        all.extend(c.deps.iter_mut());
        all.extend(c.dependents.iter_mut());
        super::attribute(&app, &mut all).await;
    }
    let files = render_files_with(&c.files, &c.bases, q.options());
    let ignore_ws = q.options().ignore_whitespace;
    let body_html =
        if c.view.body.is_empty() { String::new() } else { format!("<pre class=\"msg\">{}</pre>", render::escape(&c.view.body)) };
    Ok(Page(ChangePage { shell, repo: RepoShell::new(&app, &row, "changes").with_role(role), c, files, body_html, ignore_ws }))
}

#[derive(Template)]
#[template(path = "compare.html")]
pub struct ComparePage {
    shell: Shell,
    repo: RepoShell,
    cmp: view::Compare,
    files: Vec<FileRows>,
    ignore_ws: bool,
}

/// `/compare/{base}...{head}`.
pub async fn compare(
    State(app): State<Shared>,
    viewer: Viewer,
    Path((owner, name, spec)): Path<(String, String, String)>,
    Query(q): Query<DiffQuery>,
) -> Result<Page<ComparePage>, Error> {
    let shell = Shell::new(&app, &format!("/{owner}/{name}/compare/{spec}"), &viewer);
    let (repo, row, role) = lookup(&app, &shell, &viewer, &owner, &name).await?;
    let Some((a, b)) = spec.split_once("...") else {
        return Err(Error::bad(shell, "compare takes base...head"));
    };
    let (a, b) = (a.to_string(), b.to_string());
    let cmp = app
        .repos
        .read(&repo, move |repo, cache| {
            let base = view::resolve(repo, cache, &a)?;
            let head = view::resolve(repo, cache, &b)?;
            view::compare(repo, cache, base, head)
        })
        .await
        .map_err(|e| Error::from_repo(shell.clone(), e))?;
    let mut cmp = cmp;
    super::attribute(&app, &mut cmp.added.iter_mut().collect::<Vec<_>>()).await;
    let files = render_files_with(&cmp.files, &cmp.bases, q.options());
    let ignore_ws = q.options().ignore_whitespace;
    Ok(Page(ComparePage { shell, repo: RepoShell::new(&app, &row, "changes").with_role(role), cmp, files, ignore_ws }))
}