import { spinnerFrame } from "./spinner.ts";
import type { LocaleStrings } from "./locale.ts";
import type { ScheduleSnapshot, ScheduleState } from "./types.ts";

const CURRENT_SCOPE_ICON = "◉";
const SHARED_SCOPE_ICON = "◇";
const SCHEDULE_ICON = "⏱";
const PAUSED_ICON = "⏸";
const OVERDUE_ICON = "⚠";

export type StatusTone = "accent" | "success" | "warning" | "muted";
export type StatusStyler = (tone: StatusTone, text: string) => string;

function styled(styler: StatusStyler | undefined, tone: StatusTone, text: string): string {
	return styler ? styler(tone, text) : text;
}

function styledScope(scope: ScheduleSnapshot["scope"], styler: StatusStyler | undefined): string {
	return styled(styler, scope === "current" ? "accent" : "muted", scopeIcon(scope));
}

/**
 * 根据作用域返回状态栏图标.
 *
 * @param scope Schedule 作用域
 * @returns 作用域图标
 */
export function scopeIcon(scope: ScheduleSnapshot["scope"]): string {
	return scope === "current" ? CURRENT_SCOPE_ICON : SHARED_SCOPE_ICON;
}

/**
 * 将毫秒时长格式化为 HH:mm:ss 或 mm:ss.
 *
 * @param milliseconds 时长毫秒数
 * @returns 格式化后的时长
 */
export function formatDuration(milliseconds: number): string {
	const totalSeconds = Math.max(0, Math.floor(milliseconds / 1_000));
	const hours = Math.floor(totalSeconds / 3_600);
	const minutes = Math.floor((totalSeconds % 3_600) / 60);
	const seconds = totalSeconds % 60;
	if (hours > 0) return `${String(hours).padStart(2, "0")}:${String(minutes).padStart(2, "0")}:${String(seconds).padStart(2, "0")}`;
	return `${String(minutes).padStart(2, "0")}:${String(seconds).padStart(2, "0")}`;
}

/**
 * 将计划时间格式化为本地时间.
 *
 * 一小时内显示到秒, 更远时间显示日期和分钟, 过期时间仍保留计划时刻.
 *
 * @param timestamp 时间戳
 * @param now 当前时间
 * @param strings 当前语言文案
 * @returns 本地时间文本
 */
export function formatScheduleTime(timestamp: number, now: Date, strings: LocaleStrings): string {
	const difference = Math.abs(timestamp - now.getTime());
	const options: Intl.DateTimeFormatOptions = difference <= 3_600_000
		? { hour: "2-digit", minute: "2-digit", second: "2-digit", hour12: false }
		: { month: "2-digit", day: "2-digit", hour: "2-digit", minute: "2-digit", hour12: false };
	return new Intl.DateTimeFormat(strings.locale, options).format(new Date(timestamp));
}

/**
 * 将 Schedule 的固定间隔格式化为当前语言.
 *
 * @param schedule Schedule 快照
 * @param strings 当前语言文案
 * @returns 间隔文本
 */
export function formatCadence(schedule: ScheduleSnapshot, strings: LocaleStrings): string {
	return schedule.triggerKind === "interval" && schedule.every ? strings.every(schedule.every) : strings.once;
}

function effectiveState(schedule: ScheduleSnapshot, now: Date): ScheduleState {
	if (schedule.state === "paused") return "paused";
	if (schedule.state === "running") return "running";
	if (schedule.nextRunAt !== undefined && schedule.nextRunAt <= now.getTime()) return "overdue";
	return "scheduled";
}

function formatSingle(schedule: ScheduleSnapshot, strings: LocaleStrings, now: Date, frame: number, styler?: StatusStyler): string {
	const state = effectiveState(schedule, now);
	const scope = styledScope(schedule.scope, styler);
	if (state === "running") {
		const duration = schedule.startedAt === undefined ? "" : ` ${formatDuration(now.getTime() - schedule.startedAt)}`;
		const planned = schedule.nextRunAt === undefined ? "" : ` · ${strings.planned} ${formatScheduleTime(schedule.nextRunAt, now, strings)}`;
		return `${styled(styler, "accent", spinnerFrame(frame))} ${scope} ${schedule.name} · ${styled(styler, "accent", strings.running)}${duration}${planned}`;
	}
	if (state === "paused") return `${styled(styler, "warning", PAUSED_ICON)} ${scope} ${schedule.name} · ${styled(styler, "warning", strings.off)} · ${formatCadence(schedule, strings)}`;
	if (state === "overdue") {
		const delay = schedule.nextRunAt === undefined ? "" : ` ${formatDuration(now.getTime() - schedule.nextRunAt)}`;
		const planned = schedule.nextRunAt === undefined ? "" : ` · ${strings.planned} ${formatScheduleTime(schedule.nextRunAt, now, strings)}`;
		return `${styled(styler, "warning", OVERDUE_ICON)} ${scope} ${schedule.name} · ${styled(styler, "warning", strings.overdue)}${delay}${planned}`;
	}
	const next = schedule.nextRunAt === undefined ? "" : ` · ${strings.next} ${formatScheduleTime(schedule.nextRunAt, now, strings)}`;
	return `${styled(styler, "success", SCHEDULE_ICON)} ${scope} ${schedule.name} · ${styled(styler, "success", strings.on)} · ${formatCadence(schedule, strings)}${next}`;
}

/**
 * 将当前会话可见的 Schedule 渲染为 Footer 状态栏文本.
 *
 * @param schedules 可见 Schedule 快照
 * @param strings 当前语言文案
 * @param now 当前时间
 * @param frame spinner 帧索引
 * @param styler 可选的主题着色器
 * @returns 状态栏文本, 没有可见任务时返回 undefined
 */
export function formatStatus(
	schedules: readonly ScheduleSnapshot[],
	strings: LocaleStrings,
	now = new Date(),
	frame = 0,
	styler?: StatusStyler,
): string | undefined {
	if (schedules.length === 0) return undefined;
	if (schedules.length === 1) return formatSingle(schedules[0]!, strings, now, frame, styler);

	const states = schedules.map((schedule) => effectiveState(schedule, now));
	const running = states.filter((state) => state === "running").length;
	const overdue = states.filter((state) => state === "overdue").length;
	const paused = states.filter((state) => state === "paused").length;
	const current = schedules.filter((schedule) => schedule.scope === "current").length;
	const shared = schedules.length - current;
	const scopeParts = [
		current > 0 ? styled(styler, "accent", `${CURRENT_SCOPE_ICON} ${current}`) : undefined,
		shared > 0 ? styled(styler, "muted", `${SHARED_SCOPE_ICON} ${shared}`) : undefined,
	].filter((part): part is string => part !== undefined);
	const stateTone: StatusTone = running > 0 ? "accent" : overdue > 0 || paused === schedules.length ? "warning" : "success";
	const stateText = running > 0
		? strings.runningCount(running)
		: overdue > 0
			? strings.overdueCount(overdue)
			: paused === schedules.length
				? strings.pausedCount(paused)
				: strings.on;
	const nextRunAt = schedules.map((schedule) => schedule.nextRunAt).filter((value): value is number => value !== undefined).sort((left, right) => left - right)[0];
	const overdueRunAt = schedules
		.filter((schedule, index) => states[index] === "overdue")
		.map((schedule) => schedule.nextRunAt)
		.filter((value): value is number => value !== undefined)
		.sort((left, right) => left - right)[0];
	const timeText = overdueRunAt !== undefined
		? ` · ${strings.planned} ${formatScheduleTime(overdueRunAt, now, strings)}`
		: nextRunAt === undefined
			? ""
			: ` · ${strings.next} ${formatScheduleTime(nextRunAt, now, strings)}`;
	const rawIcon = running > 0 ? spinnerFrame(frame) : overdue > 0 ? OVERDUE_ICON : paused === schedules.length ? PAUSED_ICON : SCHEDULE_ICON;
	return `${styled(styler, stateTone, rawIcon)} ${strings.tasks(schedules.length)} · ${scopeParts.join(" · ")} · ${styled(styler, stateTone, stateText)}${timeText}`;
}