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, validateTaskFormat } from "./task-parser.ts";
import { applyCommandPrefix, getPmPrefix } from "./pm.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 applyCommandPrefix(discuss.prompt, config);
}

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)) {
    parts.push(`\n文档已存在，请先读取 ${docPath} 查看已有内容，在此基础上修订。`);
  }

  if (doc.template) {
    parts.push(`\n### 格式模板：\n${doc.template}`);
  }

  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 applyCommandPrefix(parts.join("\n"), config);
}

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",
    });
  }

  if (!config.metadata?.tracked) {
    return applyCommandPrefix(build.prompt, config);
  }

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

  let taskContent: string;
  try {
    taskContent = await readFile(taskPath, "utf-8");
  } catch {
    const prefix = getPmPrefix(config);
    throw new CommandError(`变更 "${changeName}" 尚未完成规划，task.md 不存在`, {
      hint: `请先完成规划阶段：${prefix} plan ${changeName} task 生成任务文档`,
    });
  }

  validateTaskFormat(taskContent);

  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请先读取 ${taskPath} 查看任务列表。`);
  parts.push(`当前有 ${pendingTasks.length} 个待执行任务，从第一个未完成的任务开始。`);
  parts.push(`完成后更新 ${taskPath} 中的 checkbox。`);

  return applyCommandPrefix(parts.join("\n"), config);
}

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

  if (config.metadata?.tracked) {
    const changeDir = getChangeDir(projectRoot, changeName);
    const taskPath = join(changeDir, "task.md");
    if (existsSync(taskPath)) {
      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(`请先读取 ${taskPath} 检查是否有未完成的任务。`);
          parts.push("如有未完成任务，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 读取失败时不追加警告
      }
    }
  }

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