//! `koh log` — the line, newest first.
//!
//! On a terminal this opens the history view; piped or with `--json` it prints
//! plain text, so an agent always gets something it can parse.

module cli

import json
import time
import src.history

pub fn cmd_log(raw []string) int {
	args := parse('log', raw, Options{
		values: ['since', 'session']
		flags:  ['json']
	}) or { return usage_error(err.msg()) }
	store := open_store() or { return refuse(args.json(), err.msg()) }
	defer {
		store.close()
	}
	mut cutoff := i64(0)
	if expr := args.value_or_none('since') {
		cutoff = parse_since(expr) or { return refuse(args.json(), err.msg()) }
	}
	session := args.value('session')
	head_id := history.head_id(store)
	mut shown := []history.Save{}
	for save in history.line(store) or { return refuse(args.json(), err.msg()) } {
		if cutoff > 0 && save.created_at < cutoff {
			continue
		}
		if session != '' && save.session != session {
			continue
		}
		shown << save
	}
	if args.json() {
		emit_json(json.encode(LogJson{
			head_id: head_id
			saves:   shown.map(to_json(it))
		}))
		return 0
	}
	if shown.len == 0 {
		ok('no saves in that range')
		return 0
	}
	for save in shown {
		println(log_line(save, save.id == head_id))
	}
	return 0
}

struct SaveJson {
	id            string
	parent        ?string
	message       string
	timestamp     i64
	machine       string
	agent         ?string
	session       ?string
	is_checkpoint bool
	restores      ?string
	replayed_from ?string
}

struct LogJson {
	head_id string
	saves   []SaveJson
}

fn to_json(save history.Save) SaveJson {
	return SaveJson{
		id:            save.id
		parent:        optional(save.parent)
		message:       save.message
		timestamp:     save.created_at
		machine:       save.machine
		agent:         optional(save.agent)
		session:       optional(save.session)
		is_checkpoint: save.is_checkpoint
		restores:      optional(save.restores)
		replayed_from: optional(save.replayed_from)
	}
}

fn optional(value string) ?string {
	if value == '' {
		return none
	}
	return value
}

fn log_line(save history.Save, is_head bool) string {
	marker := if is_head { amber('▸') } else { ' ' }
	mut line := '  ${marker} ${dim('[' + save.id + ']')} ${stamp(save.created_at)}  ${save.message}'
	mut tags := []string{}
	if save.agent != '' || save.session != '' {
		mut inner := []string{}
		if save.agent != '' {
			inner << save.agent
		}
		if save.session != '' {
			inner << save.session
		}
		tags << '[${inner.join(' · ')}]'
	}
	if save.is_checkpoint {
		tags << '◐'
	}
	if save.restores != '' {
		tags << '↩ ${save.restores}'
	}
	if save.replayed_from != '' {
		tags << 'replayed'
	}
	if tags.len > 0 {
		line += '  ${dim(tags.join('  '))}'
	}
	return line
}

// parse_since turns the natural-language expressions Koh has always accepted
// into a unix timestamp.
pub fn parse_since(expr string) !i64 {
	now := time.now().unix()
	text := expr.trim_space().to_lower()
	match text {
		'today' { return start_of_day(now) }
		'yesterday' { return start_of_day(now) - 86400 }
		'last week' { return now - 7 * 86400 }
		'last month' { return now - 30 * 86400 }
		'last year' { return now - 365 * 86400 }
		else {}
	}

	if date := parse_date(text) {
		return date
	}
	parts := text.split(' ')
	if parts.len >= 2 {
		amount := parts[0].int()
		if amount > 0 {
			if unit := unit_seconds(parts[1]) {
				return now - i64(amount) * unit
			}
		}
		return error('cannot understand "--since ${expr}"')
	}
	days := text.int()
	if days > 0 {
		return now - i64(days) * 86400
	}
	return error('cannot understand "--since ${expr}"')
}

fn unit_seconds(unit string) ?i64 {
	return match unit {
		'm', 'min', 'mins', 'minute', 'minutes' { i64(60) }
		'h', 'hr', 'hrs', 'hour', 'hours' { i64(3600) }
		'd', 'day', 'days' { i64(86400) }
		'w', 'week', 'weeks' { i64(7 * 86400) }
		'month', 'months' { i64(30 * 86400) }
		'y', 'year', 'years' { i64(365 * 86400) }
		else { none }
	}
}

fn parse_date(text string) ?i64 {
	parts := text.split('-')
	if parts.len != 3 || parts[0].len != 4 {
		return none
	}
	if parts[0].int() == 0 || parts[1].int() == 0 || parts[2].int() == 0 {
		return none
	}
	return midnight(parts[0].int(), parts[1].int(), parts[2].int())
}

fn start_of_day(unix_seconds i64) i64 {
	moment := time.unix(unix_seconds).local()
	return midnight(moment.year, moment.month, moment.day)
}

// midnight builds a local-time timestamp for a calendar day.
fn midnight(year int, month int, day int) i64 {
	return time.Time{
		year:     year
		month:    month
		day:      day
		is_local: true
	}.unix()
}