//! 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,

}

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 snap = self.snapshot(command)?;

        if !discard && (!snap.wc.tree_ops.is_empty() || !snap.wc.edits.is_empty()) {

            return fail("the working copy has changes; commit them first or pass --discard");

        }

        let target_state = self.load_state(heads)?;

        let heads = target_state.maximal(heads);

        let target = target_state.materialize();

        let current = self.walk_working_copy()?;

        let mut report = CheckoutReport::default();

        // Remove tracked paths that the target does not have.

        let mut dirs_to_prune: BTreeSet<PathBuf> = BTreeSet::new();

        for path in current.keys() {

            if !target.files.contains_key(path) {

                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.

        for (path, f) in &target.files {

            match &f.content {

                FileContent::Dir => continue,

                FileContent::Text { bytes, .. } => {

                    let same = current.get(path).is_some_and(|c| c.kind == NodeKind::File && &c.content == bytes && c.exec == f.mode.exec);

                    if !same {

                        self.write_file(path, bytes, f.mode.exec)?;

                        report.written += 1;

                    }

                }

                FileContent::Opaque { blobs } => {

                    let Some(blob) = blobs.first() else { continue };

                    let bytes = self.read_blob(blob)?;

                    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 && c.exec == f.mode.exec);

                        if !same {

                            self.write_file(path, &bytes, f.mode.exec)?;

                            report.written += 1;

                        }

                    }

                    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, "");

        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();

        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)

    }

    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)?;

        }

        fs::write(&full, bytes)?;

        set_executable(&full, exec)?;

        Ok(())

    }

    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(())

        }

    }

}