import { existsSync } from "node:fs";
import { readFile } from "node:fs/promises";
import { join } from "node:path";
import type { RuneConfig } from "../types.ts";
import { CommandError } from "../cli/errors.ts";
import { getChangeDir } from "./config.ts";
import { parseTasks } from "./task-parser.ts";

export function assembleDiscussPrompt(config: RuneConfig): string {
  const discuss = config.stages.discuss;
  if (!discuss) throw new CommandError("讨论阶段未配置", {
      hint: "请在 .rune/config.yaml 中配置 stages.discuss",
    });
  return discuss.prompt;
}

export async function assemblePlanPrompt(
  config: RuneConfig,
  projectRoot: string,
  changeName: string,
  documentName: string,
): Promise<string> {
  const plan = config.stages.plan;
  if (!plan) throw new CommandError("规划阶段未配置", {
      hint: "请在 .rune/config.yaml 中配置 stages.plan",
    });

  const doc = plan.documents.find((d) => d.name === documentName);
  if (!doc) {
    throw new CommandError(`文档 "${documentName}" 不在配置的 plan.documents 中`, {
      hint: `可用文档：${plan.documents.map((d) => d.name).join(", ")}`,
    });
  }

  const changeDir = getChangeDir(projectRoot, changeName);
  const parts: string[] = [];

  parts.push(`# 规划阶段：${changeName}`);
  parts.push("");
  parts.push(`## 文档：${doc.name}.md`);
  parts.push(doc.prompt);

  const docPath = join(changeDir, `${doc.name}.md`);
  if (existsSync(docPath)) {
    const existing = await readFile(docPath, "utf-8");
    parts.push(`\n### 已有内容（请在此基础上修订）：\n${existing}`);
  }

  if (doc.template) {
    const rendered = doc.template.replace(/\{\{change-name\}\}/g, changeName);
    parts.push(`\n### 格式模板：\n${rendered}`);
  }

  if (doc.depend && doc.depend.length > 0) {
    parts.push("\n---\n");
    parts.push("## 依赖说明\n");
    parts.push("本文档依赖以下前置文档：");

    for (const dep of doc.depend) {
      const depPath = join(changeDir, `${dep}.md`);
      const depCompleted = existsSync(depPath);
      const status = depCompleted ? "已完成" : "未完成";
      parts.push(`- ${dep}.md（${status}）`);
    }

    parts.push("\n请先阅读已完成的前置文档，确保内容一致。");
  }

  parts.push(`\n请将文档写入目录：${changeDir}`);
  return parts.join("\n");
}

export async function assembleBuildPrompt(
  config: RuneConfig,
  projectRoot: string,
  changeName: string,
): Promise<string> {
  const build = config.stages.build;
  if (!build) {
    throw new CommandError("构建阶段未配置", {
      hint: "请在 .rune/config.yaml 中配置 stages.build",
    });
  }

  const changeDir = getChangeDir(projectRoot, changeName);
  const taskPath = join(changeDir, "task.md");

  let taskContent: string;
  try {
    taskContent = await readFile(taskPath, "utf-8");
  } catch {
    throw new CommandError(`变更 "${changeName}" 尚未完成规划，task.md 不存在`, {
      hint: `请先完成规划阶段：rune plan ${changeName} 生成所有规划文档`,
    });
  }

  const tasks = parseTasks(taskContent);
  const pendingTasks = tasks.filter((t) => !t.checked);

  if (pendingTasks.length === 0) {
    return `所有任务已完成。变更 "${changeName}" 可以归档。`;
  }

  const parts: string[] = [];
  parts.push(`# 构建阶段：${changeName}\n`);
  parts.push(build.prompt);
  parts.push(`\n## 任务列表\n`);
  parts.push(taskContent);
  parts.push(`\n## 待执行任务（共 ${pendingTasks.length} 项）`);
  for (const task of pendingTasks) {
    parts.push(`- [ ] ${task.text}`);
  }
  parts.push(
    `\n请从第一个待执行任务开始。完成后更新 ${taskPath} 中的 checkbox。`,
  );

  return parts.join("\n");
}

export async function assembleArchivePrompt(
  config: RuneConfig,
  projectRoot: string,
  changeName: string,
): Promise<string> {
  const archive = config.stages.archive;
  if (!archive) throw new CommandError("归档阶段未配置", {
      hint: "请在 .rune/config.yaml 中配置 stages.archive",
    });

  const changeDir = getChangeDir(projectRoot, changeName);
  const taskPath = join(changeDir, "task.md");

  const parts: string[] = [];
  parts.push(`# 归档阶段：${changeName}\n`);

  try {
    const taskContent = await readFile(taskPath, "utf-8");
    const tasks = parseTasks(taskContent);
    const incompleteTasks = tasks.filter((t) => !t.checked);
    if (incompleteTasks.length > 0) {
      parts.push("## ⚠️ 警告：存在未完成的任务\n");
      parts.push(`以下 ${incompleteTasks.length} 个任务尚未完成：`);
      for (const t of incompleteTasks) {
        parts.push(`- [ ] ${t.text}`);
      }
      parts.push("");
      parts.push("请询问用户是否确认在任务未全部完成的情况下归档。");
      parts.push("如用户确认，则继续归档；否则中止并返回构建阶段。");
      parts.push("");
    }
  } catch {
    // task.md 不存在时不追加警告
  }

  parts.push(archive.prompt);
  return parts.join("\n");
}