//! Moving the working copy to another state (spec §12.3, §7.7).

use super::*;

#[derive(Debug, Default, Clone, PartialEq, Eq)]
pub struct CheckoutReport {
    pub written: usize,
    pub removed: usize,
    pub conflicted: bool,
    /// Nested repositories that could not be moved, and other remarks.
    pub notes: Vec<String>,
}

impl Repo {
    /// Move the working copy to the state whose heads are `heads` (spec §12.3):
    /// the working directory is rewritten to that state and a fresh
    /// working-copy change is started on it. The bookmark does not move.
    pub fn checkout(
        &self,
        heads: &[ChangeHash],
        discard: bool,
        command: &str,
    ) -> Result<CheckoutReport> {
        let _wc = self.lock_working_copy()?;
        let snap = self.snapshot(command)?;
        if !discard && (!snap.wc.tree_ops.is_empty() || !snap.wc.edits.is_empty()) {
            let list: Vec<String> = snap
                .statuses
                .iter()
                .take(8)
                .map(|s| format!("{} {}", status_word(s.status), s.path))
                .collect();
            return fail(format!(
                "the working copy has changes ({}{}); commit them, take them along with --carry, or drop them with --discard",
                list.join(", "),
                if snap.statuses.len() > 8 { ", …" } else { "" }
            ));
        }
        let target_state = self.load_state(heads)?;
        let heads = target_state.maximal(heads);
        let target = target_state.materialize();
        let attrs = Repo::state_attributes(&target);
        let current = self.walk_working_copy()?;
        let mut report = CheckoutReport::default();
        // Paths this file system cannot hold side by side (spec §7.7).
        report.notes.extend(
            self.platform
                .problems(target.files.keys().map(String::as_str)),
        );

        // Remove tracked paths that the target does not have. A nested
        // repository is never deleted (spec §7.8); it is left in place.
        let mut dirs_to_prune: BTreeSet<PathBuf> = BTreeSet::new();
        for (path, entry) in &current {
            if !target.files.contains_key(path) {
                if entry.kind == NodeKind::Subrepo {
                    report
                        .notes
                        .push(format!("{path}: nested repository left in place"));
                    continue;
                }
                let full = self.safe_path(path)?;
                fs::remove_file(&full)?;
                report.removed += 1;
                if let Some(parent) = full.parent() {
                    dirs_to_prune.insert(parent.to_path_buf());
                }
            }
        }
        // Write target files that differ (only inside the sparse filter).
        for (path, f) in &target.files {
            if !self.in_scope(path) {
                continue;
            }
            match &f.content {
                FileContent::Dir => continue,
                FileContent::Text { bytes, .. } => {
                    let a = attrs.lookup(path);
                    let on_disk: std::borrow::Cow<[u8]> =
                        if a.eol == Some(crate::attributes::Eol::Crlf) {
                            crate::attributes::to_crlf(bytes).into()
                        } else {
                            bytes.as_slice().into()
                        };
                    let same = current.get(path).is_some_and(|c| {
                        c.kind == NodeKind::File
                            && c.content == *on_disk
                            && (!self.platform.exec_bits || c.exec == f.mode.exec)
                    });
                    if !same {
                        self.write_file(path, &on_disk, f.mode.exec)?;
                        report.written += 1;
                    }
                    if a.lockable && !self.is_locked(path) {
                        let _ = set_readonly(&self.root.join(path), true);
                    }
                }
                FileContent::Opaque { blobs } => {
                    let Some(blob) = blobs.first() else { continue };
                    let bytes = self.read_blob(blob)?;
                    if f.kind == NodeKind::Subrepo {
                        let pin = crate::subrepo::Pin::decode(&bytes)?;
                        match self.sync_subrepo(path, &pin, false)? {
                            SubrepoSync::Updated => report.written += 1,
                            SubrepoSync::UpToDate => {}
                            SubrepoSync::Missing => report.notes.push(format!("{path}: nested repository not present; run oxy submodule update --init")),
                            SubrepoSync::Dirty => report.notes.push(format!("{path}: nested repository has uncommitted changes; left as is")),
                            SubrepoSync::Failed(e) => report.notes.push(format!("{path}: {e}")),
                        }
                        continue;
                    }
                    if f.kind == NodeKind::Symlink {
                        let same = current
                            .get(path)
                            .is_some_and(|c| c.kind == NodeKind::Symlink && c.content == bytes);
                        if !same {
                            self.write_symlink(path, &bytes)?;
                            report.written += 1;
                        }
                    } else {
                        let same = current.get(path).is_some_and(|c| {
                            c.kind == NodeKind::File
                                && c.content == bytes
                                && (!self.platform.exec_bits || c.exec == f.mode.exec)
                        });
                        if !same {
                            self.write_file(path, &bytes, f.mode.exec)?;
                            report.written += 1;
                        }
                        if attrs.lookup(path).lockable && !self.is_locked(path) {
                            let _ = set_readonly(&self.root.join(path), true);
                        }
                    }
                    if blobs.len() > 1 {
                        for (i, b) in blobs.iter().enumerate().skip(1) {
                            self.write_file(
                                &format!("{path}.oxy-conflict-{}", i + 1),
                                &self.read_blob(b)?,
                                f.mode.exec,
                            )?;
                        }
                    }
                }
            }
        }
        // Prune directories left empty, deepest first.
        for d in dirs_to_prune.iter().rev() {
            let mut d = d.clone();
            while d != self.root
                && fs::read_dir(&d)
                    .map(|mut i| i.next().is_none())
                    .unwrap_or(false)
            {
                fs::remove_dir(&d)?;
                let Some(p) = d.parent() else { break };
                d = p.to_path_buf();
            }
        }

        let (op_ref, op) = self.head_op()?;
        let wc = self.new_working_copy(heads.clone(), "");
        let wc_hash = self.store.put_change(&wc)?;
        let mut view = op.view.clone();
        view.workspaces.insert(self.workspace, wc_hash);
        self.record_op(&[op_ref], command, view)?;
        report.conflicted = target.is_conflicted();
        let blobs: HashMap<String, ObjectRef> = target
            .files
            .iter()
            .filter_map(|(p, f)| match &f.content {
                FileContent::Opaque { blobs } if f.kind == NodeKind::File && blobs.len() == 1 => {
                    Some((p.clone(), blobs[0]))
                }
                _ => None,
            })
            .collect();
        let entries = self.walk_working_copy_with(None, &Self::tracked_kinds(&target), None)?;
        self.write_manifest_entries(report.conflicted, false, &entries, &blobs)?;
        let _ = self.run_hook(
            "post-checkout",
            &format!(
                "{{\"event\":\"post-checkout\",\"heads\":{},\"written\":{},\"removed\":{}}}",
                json_array(heads.iter().map(|h| json_str(&h.to_hex()))),
                report.written,
                report.removed
            ),
        );
        Ok(report)
    }

    /// The absolute path for a repository path, refusing anything that would
    /// escape the workspace or write through a symlink (spec §7.7).
    fn safe_path(&self, rel: &str) -> Result<PathBuf> {
        let mut full = self.root.clone();
        let comps: Vec<&str> = rel.split('/').collect();
        for (i, comp) in comps.iter().enumerate() {
            if comp.is_empty() || *comp == "." || *comp == ".." || comp.contains('\\') {
                return fail(format!("refusing unsafe path {rel:?}"));
            }
            if i == 0 && *comp == OXY_DIR {
                return fail(format!("refusing to write inside {OXY_DIR}: {rel:?}"));
            }
            if i + 1 < comps.len() {
                full.push(comp);
                if let Ok(m) = fs::symlink_metadata(&full) {
                    if m.file_type().is_symlink() {
                        return fail(format!(
                            "refusing to write through symlink {}",
                            full.display()
                        ));
                    }
                }
            } else {
                full.push(comp);
            }
        }
        Ok(full)
    }

    pub(crate) fn write_file(&self, rel: &str, bytes: &[u8], exec: bool) -> Result<()> {
        let full = self.safe_path(rel)?;
        if let Some(parent) = full.parent() {
            fs::create_dir_all(parent)?;
        }
        if fs::symlink_metadata(&full).is_ok_and(|m| m.file_type().is_symlink() || m.is_dir()) {
            remove_any(&full)?;
        }
        if fs::metadata(&full).is_ok_and(|m| m.permissions().readonly()) {
            set_readonly(&full, false)?;
        }
        fs::write(&full, bytes)?;
        set_executable(&full, exec)?;
        Ok(())
    }

    pub(crate) fn write_symlink(&self, rel: &str, target: &[u8]) -> Result<()> {
        let full = self.safe_path(rel)?;
        if let Some(parent) = full.parent() {
            fs::create_dir_all(parent)?;
        }
        if fs::symlink_metadata(&full).is_ok() {
            remove_any(&full)?;
        }
        #[cfg(unix)]
        {
            std::os::unix::fs::symlink(String::from_utf8_lossy(target).as_ref(), &full)?;
            Ok(())
        }
        #[cfg(not(unix))]
        {
            // Spec §7.7: without symlink support, write the target as a plain file.
            fs::write(&full, target)?;
            Ok(())
        }
    }
}

/// How a refusal names a path's change: "removed" is a file of the working
/// copy's base that is missing on disk.
fn status_word(s: ChangeStatus) -> &'static str {
    match s {
        ChangeStatus::Added => "added",
        ChangeStatus::Modified => "modified",
        ChangeStatus::Removed => "removed",
        ChangeStatus::Renamed => "renamed",
        ChangeStatus::ModeChanged => "mode changed",
        ChangeStatus::ConflictEdited => "conflict edited",
        ChangeStatus::Resolved => "resolved",
    }
}