//! LOG.md: the one-screen history Koh keeps at the repo root for people (and
//! agents) who want the last few saves without running a command.

module history

import os
import time
import src.storage

const log_marker = '<!-- Koh maintains this file. Do not edit. Read before starting work. -->'
const log_shown = 20

// refresh_log_md rewrites LOG.md after a change to history has landed.
// The history is what matters, so a LOG.md that cannot be written is a warning
// on stderr, never a failed command: a save that exits 1 after landing would
// send an agent to save again.
pub fn refresh_log_md(store &storage.Store) {
	write_log_md(store) or { eprintln('  ! LOG.md was not updated: ${err.msg()}') }
}

// write_log_md refreshes LOG.md from the line. It runs after every save,
// whatever made it — save, checkpoint, undo, load, revert, pluck or a steal.
fn write_log_md(store &storage.Store) ! {
	path := os.join_path(store.root, 'LOG.md')
	if os.is_file(path) {
		existing := os.read_file(path)!
		if !existing.starts_with(log_marker) {
			// Someone else's log file; leave it alone.
			return
		}
	}
	saves := line(store)!
	shown := if saves.len < log_shown { saves.len } else { log_shown }
	mut text := '${log_marker}\n\n# Koh Log\n\n'
	for save in saves[..shown] {
		text += '✦ [${save.id}]  ${save.message} · ${clock(save.created_at)}\n'
	}
	if saves.len > shown {
		text += '\n… ${saves.len - shown} older saves\n'
	}
	text += '\n*full history: koh view*\n'
	os.write_file(path, text)!
}

fn clock(unix_seconds i64) string {
	return time.unix(unix_seconds).local().format_ss()
}