//! Writing a tree back onto disk.
//!
//! A restore writes exactly the target's files and deletes the tracked files
//! the target does not have. Ignored paths are never touched, and every file
//! lands through a temp file and a rename, so an interrupted restore leaves a
//! readable tree rather than half-written files.

module snapshot

import os
import src.storage

pub struct RestoreReport {
pub:
	written int
	removed int
}

// restore_files writes exactly `target` into the working tree and deletes the
// paths in `remove` (tracked files the target does not have). Ignored paths are
// never touched — not written, not deleted — even if a caller asks. Every file
// lands through a temp file and a rename, so an interrupted restore leaves a
// readable tree rather than half-written files.
pub fn restore_files(store &storage.Store, root string, ig Ignore, target []FileEntry, remove []string) !RestoreReport {
	mut wanted := map[string]bool{}
	for entry in target {
		wanted[entry.path] = true
	}
	mut removed := 0
	for path in remove {
		full := os.join_path(root, path)
		if !os.is_file(full) || ig.matches(path, false) || path in wanted {
			continue
		}
		os.rm(full)!
		removed++
		prune_empty_dirs(root, os.dir(full))
	}
	for entry in target {
		data := store.get_object(entry.hash)!
		write_file(os.join_path(root, entry.path), data, entry.executable)!
	}
	return RestoreReport{
		written: target.len
		removed: removed
	}
}

fn write_file(path string, data []u8, executable bool) ! {
	os.mkdir_all(os.dir(path), os.MkdirParams{})!
	tmp := '${path}.koh-tmp-${os.getpid()}'
	os.write_file_array(tmp, data)!
	mode := if executable { 0o755 } else { 0o644 }
	os.chmod(tmp, mode)!
	os.mv(tmp, path, os.MvParams{})!
}

// prune_empty_dirs clears directories a restore emptied, never the repo root.
fn prune_empty_dirs(root string, dir string) {
	mut current := dir
	for current.len > root.len && current.starts_with(root) {
		if (os.ls(current) or { return }).len > 0 {
			return
		}
		os.rmdir(current) or { return }
		current = os.dir(current)
	}
}