import type { CalcHistoryCreate, CalcHistoryEntry } from "@/lib/history/types";

async function parseApiError(res: Response): Promise<string> {
  try {
    const data = (await res.json()) as { error?: string };
    return data.error ?? `请求失败 (${res.status})`;
  } catch {
    return `请求失败 (${res.status})`;
  }
}

export async function loadHistory(): Promise<CalcHistoryEntry[]> {
  const res = await fetch("/api/history", { cache: "no-store" });
  if (!res.ok) {
    throw new Error(await parseApiError(res));
  }
  const data = (await res.json()) as { items: CalcHistoryEntry[] };
  return data.items ?? [];
}

export async function saveHistoryEntry(
  entry: CalcHistoryCreate,
): Promise<CalcHistoryEntry> {
  const res = await fetch("/api/history", {
    method: "POST",
    cache: "no-store",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify(entry),
  });
  if (!res.ok) {
    throw new Error(await parseApiError(res));
  }
  const data = (await res.json()) as { entry: CalcHistoryEntry };
  return data.entry;
}

export async function saveHistoryEntrySafe(
  entry: CalcHistoryCreate,
): Promise<
  { ok: true; entry: CalcHistoryEntry } | { ok: false; error: string }
> {
  try {
    const saved = await saveHistoryEntry(entry);
    return { ok: true, entry: saved };
  } catch (err) {
    return {
      ok: false,
      error: err instanceof Error ? err.message : String(err),
    };
  }
}

export async function deleteHistoryEntry(id: string): Promise<void> {
  const res = await fetch(`/api/history/${encodeURIComponent(id)}`, {
    method: "DELETE",
    cache: "no-store",
  });
  if (!res.ok) {
    throw new Error(await parseApiError(res));
  }
}

export function downloadMarkdown(content: string, filename: string) {
  const blob = new Blob([content], { type: "text/markdown;charset=utf-8" });
  const url = URL.createObjectURL(blob);
  const a = document.createElement("a");
  a.href = url;
  a.download = filename.endsWith(".md") ? filename : `${filename}.md`;
  a.click();
  URL.revokeObjectURL(url);
}

function formatBaziInputLines(entry: CalcHistoryEntry): string[] {
  if (!entry.baziInput) {
    return [];
  }
  const { baziInput } = entry;
  const gender = baziInput.gender === "male" ? "男" : "女";
  const hour = baziInput.unknownHour ? "时辰不详" : baziInput.time;
  return [
    `- 出生地域：${baziInput.birthPlaceName}`,
    `- 阳历生日：${baziInput.date} ${hour}`,
    `- 性别：${gender}`,
  ];
}

function formatBaziChartLines(entry: CalcHistoryEntry): string[] {
  if (!entry.baziChart) {
    return [];
  }
  const { baziChart } = entry;
  const { pillars } = baziChart;
  return [
    `- 农历：${baziChart.lunarDate}`,
    `- 四柱：${pillars.year.ganZhi} ${pillars.month.ganZhi} ${pillars.day.ganZhi} ${pillars.time.ganZhi}`,
    `- 真太阳时：${baziChart.trueSolarTime}`,
  ];
}

export function buildHistoryMarkdown(entry: CalcHistoryEntry): string {
  const lines = [
    `# ${entry.title}`,
    "",
    `- 类型：${entry.mode}`,
    `- 时间：${new Date(entry.createdAt).toLocaleString("zh-CN")}`,
    `- 问事：${entry.question}`,
    "",
    ...formatBaziInputLines(entry),
    ...formatBaziChartLines(entry),
    ...Object.entries(entry.meta)
      .filter(([key]) => !["出生地域", "阳历生日", "农历", "性别"].includes(key))
      .map(([k, v]) => `- ${k}：${v}`),
  ];

  if (entry.hexagram) {
    lines.push(
      `- 卦象：${entry.hexagram.guaTitle}`,
      `- 卦辞：${entry.hexagram.guaResult}`,
    );
  }

  lines.push("", "---", "", entry.completion);
  return lines.join("\n");
}