//! Subrepositories in the working copy (spec §7.8): reading pins from
//! nested repositories, moving them to pins, and the `oxy submodule`
//! commands.

use super::*;
use crate::subrepo::{Module, Modules, Pin};
use std::process::Command;

/// What syncing a nested repository to its pin did.
#[derive(Clone, Debug, PartialEq, Eq)]
pub enum SubrepoSync {
    Updated,
    UpToDate,
    Missing,
    Dirty,
    /// The working copy was brought to the pin, but the nested repository's
    /// bookmark has changes the pin lacks, so it was left where it is: a
    /// bookmark is never moved backwards (spec §7.8).
    KeptBookmark {
        bookmark: String,
        newer: usize,
    },
    Failed(String),
}

impl SubrepoSync {
    /// A note for a checkout report, when there is something to say.
    pub fn note(&self, path: &str) -> Option<String> {
        match self {
            SubrepoSync::Updated | SubrepoSync::UpToDate => None,
            SubrepoSync::Missing => Some(format!(
                "{path}: nested repository not present; run oxy submodule update --init"
            )),
            SubrepoSync::Dirty => Some(format!(
                "{path}: nested repository has uncommitted changes; left as is"
            )),
            SubrepoSync::KeptBookmark { bookmark, newer } => Some(format!(
                "{path}: checked out at the pin; its bookmark {bookmark} keeps {newer} newer change{} (oxy bookmark switch {bookmark} there to return to them)",
                if *newer == 1 { "" } else { "s" }
            )),
            SubrepoSync::Failed(e) => Some(format!("{path}: {e}")),
        }
    }
}

/// One subrepo as `oxy submodule status` shows it.
#[derive(Clone, Debug)]
pub struct SubrepoInfo {
    pub path: String,
    pub pin: Pin,
    pub url: Option<String>,
    /// The nested repository's own pin now, if present.
    pub actual: Option<Pin>,
    pub dirty: bool,
    /// Whether the working copy's base records it. An added subrepo
    /// (registered in `.oxymodules`, not committed yet) has `pin` set to
    /// what the next commit records.
    pub committed: bool,
}

fn git_out(dir: &Path, args: &[&str]) -> Result<String> {
    let out = Command::new("git")
        .arg("-C")
        .arg(dir)
        .args(args)
        .output()
        .map_err(|e| RepoError::Msg(format!("running git: {e}")))?;
    if !out.status.success() {
        return fail(format!(
            "git {} in {}: {}",
            args.join(" "),
            dir.display(),
            String::from_utf8_lossy(&out.stderr).trim()
        ));
    }
    Ok(String::from_utf8_lossy(&out.stdout).trim().to_string())
}

/// The pin a nested repository at `dir` is at: the base of its working
/// copy for an Oxygen repository (which is its bookmark's heads unless a
/// parent checked out an older pin), `HEAD` for a Git one.
pub(crate) fn read_pin(dir: &Path, bookmark_hint: Option<&str>) -> Result<Pin> {
    if dir.join(OXY_DIR).exists() {
        let nested = Repo::open(dir)?;
        return Ok(Pin::Oxy {
            repo: nested.id()?,
            heads: nested.working_copy()?.1.deps,
            bookmark: nested.config.bookmark.clone(),
        });
    }
    if dir.join(".git").exists() {
        let sha = git_out(dir, &["rev-parse", "HEAD"])?;
        return Ok(Pin::Git {
            sha,
            branch: bookmark_hint.unwrap_or("HEAD").to_string(),
        });
    }
    fail(format!("{} is not a repository", dir.display()))
}

/// Whether a nested repository has uncommitted work.
fn nested_dirty(dir: &Path) -> Result<bool> {
    if dir.join(OXY_DIR).exists() {
        let nested = Repo::open(dir)?;
        let snap = nested.snapshot("oxy submodule")?;
        return Ok(!snap.wc.tree_ops.is_empty() || !snap.wc.edits.is_empty());
    }
    Ok(!git_out(dir, &["status", "--porcelain"])?.is_empty())
}

/// Whether `url` is an Oxygen repository (else it is taken to be Git),
/// probed with `options`, the credentials a clone of it would use; with
/// the probe's error when it is not, to report if Git cannot clone it
/// either.
fn probe_oxy_url(url: &str, options: &RemoteOptions) -> std::result::Result<(), String> {
    if url.starts_with("http://") || url.starts_with("https://") {
        return crate::protocol::open_remote(url, options)
            .and_then(|r| r.repo_id())
            .map(|_| ())
            .map_err(|e| e.to_string());
    }
    let p = Path::new(url.strip_prefix("file://").unwrap_or(url));
    if p.join(OXY_DIR).exists() {
        Ok(())
    } else {
        Err(format!("{} has no {OXY_DIR} directory", p.display()))
    }
}

impl Repo {
    pub(crate) fn modules_on_disk(&self) -> Modules {
        fs::read_to_string(self.root.join(".oxymodules"))
            .map(|t| Modules::parse(&t))
            .unwrap_or_default()
    }

    fn write_modules(&self, m: &Modules) -> Result<()> {
        if m.entries.is_empty() {
            let _ = fs::remove_file(self.root.join(".oxymodules"));
            return Ok(());
        }
        write_atomic(&self.root.join(".oxymodules"), m.to_text().as_bytes())
    }

    /// Bring the nested repository at `path` to `pin`, cloning it first when
    /// `init` and it is absent.
    pub(crate) fn sync_subrepo(&self, path: &str, pin: &Pin, init: bool) -> Result<SubrepoSync> {
        let dir = self.root.join(path);
        let module = self.modules_on_disk().entries.get(path).cloned();
        let present = dir.join(OXY_DIR).exists() || dir.join(".git").exists();
        let cloned = !present;
        if !present {
            if !init {
                return Ok(SubrepoSync::Missing);
            }
            let Some(m) = &module else {
                return Ok(SubrepoSync::Failed(
                    "no .oxymodules entry to clone from".into(),
                ));
            };
            if let Some(parent) = dir.parent() {
                fs::create_dir_all(parent)?;
            }
            let _ = fs::remove_dir(&dir);
            let r = match pin {
                Pin::Oxy { .. } => self.clone_as_subrepo(&m.url, &dir).map(|_| ()),
                Pin::Git { .. } => Command::new("git")
                    .args(["clone", "-q", &m.url])
                    .arg(&dir)
                    .status()
                    .map_err(|e| RepoError::Msg(e.to_string()))
                    .and_then(|s| {
                        if s.success() {
                            Ok(())
                        } else {
                            fail(format!("git clone {} failed", m.url))
                        }
                    }),
            };
            if let Err(e) = r {
                return Ok(SubrepoSync::Failed(format!("cloning {}: {e}", m.url)));
            }
        }
        let actual = read_pin(&dir, module.as_ref().and_then(|m| m.bookmark.as_deref()))?;
        let same = match (pin, &actual) {
            (Pin::Oxy { heads: a, .. }, Pin::Oxy { heads: b, .. }) => {
                let (mut a, mut b) = (a.clone(), b.clone());
                a.sort();
                b.sort();
                a == b
            }
            (Pin::Git { sha: a, .. }, Pin::Git { sha: b, .. }) => a == b,
            _ => false,
        };
        if same {
            return Ok(if cloned {
                SubrepoSync::Updated
            } else {
                SubrepoSync::UpToDate
            });
        }
        if nested_dirty(&dir)? {
            return Ok(SubrepoSync::Dirty);
        }
        match pin {
            Pin::Oxy { heads, .. } => {
                let nested = Repo::open(&dir)?;
                if nested.load_state(heads).is_err() {
                    // The pinned changes are not here yet: fetch from origin.
                    if let Err(e) = nested.fetch("origin") {
                        return Ok(SubrepoSync::Failed(format!(
                            "fetching the pinned changes: {e}"
                        )));
                    }
                }
                match nested.checkout(heads, false, "oxy submodule update") {
                    Ok(_) => {
                        // Its bookmark follows only forward: work it has
                        // beyond the pin stays on it (metalgear, oxygen#38).
                        let bookmark = nested.config.bookmark.clone();
                        let at = nested.bookmark_heads().unwrap_or_default();
                        let newer = nested.state_gap(&at, heads).map(|g| g.lacks).unwrap_or(0);
                        if newer == 0 {
                            let _ = nested.bookmark_set(&bookmark, heads);
                            Ok(SubrepoSync::Updated)
                        } else {
                            Ok(SubrepoSync::KeptBookmark { bookmark, newer })
                        }
                    }
                    Err(e) => Ok(SubrepoSync::Failed(e.to_string())),
                }
            }
            Pin::Git { sha, .. } => {
                if git_out(&dir, &["cat-file", "-e", &format!("{sha}^{{commit}}")]).is_err() {
                    if let Err(e) = git_out(&dir, &["fetch", "-q", "origin"]) {
                        return Ok(SubrepoSync::Failed(e.to_string()));
                    }
                }
                match git_out(&dir, &["checkout", "-q", "--detach", sha]) {
                    Ok(_) => Ok(SubrepoSync::Updated),
                    Err(e) => Ok(SubrepoSync::Failed(e.to_string())),
                }
            }
        }
    }

    /// Every subrepo of the working copy's base state.
    pub fn subrepos(&self) -> Result<Vec<SubrepoInfo>> {
        let (_, wc) = self.working_copy()?;
        let snap = self.load_state(&wc.deps)?.materialize();
        let modules = self.modules_on_disk();
        let mut out = Vec::new();
        for (path, f) in &snap.files {
            if f.kind != NodeKind::Subrepo {
                continue;
            }
            let FileContent::Opaque { blobs } = &f.content else {
                continue;
            };
            let Some(b) = blobs.first() else { continue };
            let pin = Pin::decode(&self.read_blob(b)?)?;
            let dir = self.root.join(path);
            let present = dir.join(OXY_DIR).exists() || dir.join(".git").exists();
            let actual = if present {
                read_pin(
                    &dir,
                    modules
                        .entries
                        .get(path)
                        .and_then(|m| m.bookmark.as_deref()),
                )
                .ok()
            } else {
                None
            };
            let dirty = present && nested_dirty(&dir).unwrap_or(false);
            out.push(SubrepoInfo {
                path: path.clone(),
                pin,
                url: modules.entries.get(path).map(|m| m.url.clone()),
                actual,
                dirty,
                committed: true,
            });
        }
        // Registered but not committed yet: pinned at what they are now.
        for (path, m) in &modules.entries {
            if snap.files.contains_key(path) {
                continue;
            }
            let dir = self.root.join(path);
            let Ok(pin) = read_pin(&dir, m.bookmark.as_deref()) else {
                continue;
            };
            out.push(SubrepoInfo {
                path: path.clone(),
                pin: pin.clone(),
                url: Some(m.url.clone()),
                actual: Some(pin),
                dirty: nested_dirty(&dir).unwrap_or(false),
                committed: false,
            });
        }
        out.sort_by(|a, b| a.path.cmp(&b.path));
        Ok(out)
    }

    /// `.oxymodules` entries with no subrepo behind them: never added, so
    /// there is no pin to clone or check out (oxygen#72).
    pub fn unpinned_modules(&self) -> Result<Vec<(String, Module)>> {
        let pinned: Vec<String> = self.subrepos()?.into_iter().map(|s| s.path).collect();
        Ok(self
            .modules_on_disk()
            .entries
            .into_iter()
            .filter(|(path, _)| !pinned.contains(path))
            .collect())
    }

    /// Clone `url` at `path`, register it in `.oxymodules`, and return the
    /// pin the next snapshot will record.
    pub fn submodule_add(&self, url: &str, path: &str, bookmark: Option<&str>) -> Result<Pin> {
        let path = path.trim_end_matches('/').to_string();
        if path.is_empty()
            || path.starts_with('/')
            || path.split('/').any(|c| c == ".." || c == ".")
        {
            return fail(format!("{path:?} is not a valid subrepo path"));
        }
        let dir = self.root.join(&path);
        if dir.exists() && fs::read_dir(&dir)?.next().is_some() {
            return fail(format!("{path} exists and is not empty"));
        }
        if let Some(parent) = dir.parent() {
            fs::create_dir_all(parent)?;
        }
        let probe = probe_oxy_url(url, &self.credentials_for(url));
        let git = probe.is_err();
        if git {
            let mut cmd = Command::new("git");
            cmd.args(["clone", "-q"]);
            if let Some(b) = bookmark {
                cmd.args(["--branch", b]);
            }
            let status = cmd
                .arg(url)
                .arg(&dir)
                .status()
                .map_err(|e| RepoError::Msg(format!("running git: {e}")))?;
            if !status.success() {
                let oxy_error = probe.err().unwrap_or_default();
                return fail(format!(
                    "git clone {url} failed; as an Oxygen repository: {oxy_error}"
                ));
            }
        } else {
            let _ = fs::remove_dir(&dir);
            let mut nested = self.clone_as_subrepo(url, &dir)?;
            if let Some(b) = bookmark {
                nested.bookmark_switch(b, true)?;
            }
        }
        let mut modules = self.modules_on_disk();
        modules.entries.insert(
            path.clone(),
            Module {
                url: url.to_string(),
                bookmark: bookmark.map(str::to_string),
                git,
            },
        );
        self.write_modules(&modules)?;
        read_pin(&dir, bookmark)
    }

    /// Bring nested repositories to their pins (`paths` empty = all).
    pub fn submodule_update(
        &self,
        init: bool,
        paths: &[String],
    ) -> Result<Vec<(String, SubrepoSync)>> {
        let mut out = Vec::new();
        for s in self.subrepos()? {
            if !paths.is_empty() && !paths.iter().any(|p| p.trim_end_matches('/') == s.path) {
                continue;
            }
            let r = self.sync_subrepo(&s.path, &s.pin, init)?;
            out.push((s.path, r));
        }
        Ok(out)
    }

    /// Drop the `.oxymodules` entry; the node goes with the next snapshot
    /// only if the directory is removed, since a registered or tracked
    /// nested repository keeps contributing its pin. Here the directory is
    /// left in place and the node is removed explicitly from the working
    /// copy's next change by unregistering and moving the directory aside.
    pub fn submodule_remove(&self, path: &str) -> Result<()> {
        let path = path.trim_end_matches('/').to_string();
        let mut modules = self.modules_on_disk();
        let known = modules.entries.remove(&path).is_some()
            || self.subrepos()?.iter().any(|s| s.path == path);
        if !known {
            return fail(format!("{path} is not a subrepo"));
        }
        self.write_modules(&modules)?;
        // The directory stays; the walker ignores an unregistered nested
        // repository unless tracked, so mark it as removed for the next
        // snapshot by recording an explicit removal.
        let dir = self.oxy.join("subrepos-removed");
        fs::create_dir_all(&dir)?;
        write_atomic(&dir.join(path.replace('/', "%2F")), b"")?;
        Ok(())
    }

    /// Paths whose subrepo node was removed with `oxy submodule remove` and
    /// whose directory is still on disk.
    pub(crate) fn removed_subrepos(&self) -> BTreeSet<String> {
        let mut out = BTreeSet::new();
        if let Ok(rd) = fs::read_dir(self.oxy.join("subrepos-removed")) {
            for e in rd.flatten() {
                out.insert(e.file_name().to_string_lossy().replace("%2F", "/"));
            }
        }
        out
    }

    pub(crate) fn clear_removed_subrepo(&self, path: &str) {
        let _ = fs::remove_file(
            self.oxy
                .join("subrepos-removed")
                .join(path.replace('/', "%2F")),
        );
    }
}