import { existsSync } from "node:fs";
import { readFile } from "node:fs/promises";
import { join } from "node:path";
import type { RuneConfig } from "../types.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 Error("discuss 阶段未配置");
  return discuss.prompt;
}

export async function assemblePlanPrompt(
  config: RuneConfig,
  projectRoot: string,
  changeName: string,
): Promise<string> {
  const plan = config.stages.plan;
  if (!plan) throw new Error("plan 阶段未配置");

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

  parts.push(`# 规划阶段：${changeName}\n`);
  parts.push("请为当前变更生成以下文档：\n");

  for (const doc of plan.documents) {
    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}`);
    }

    parts.push("");
  }

  parts.push(`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 Error("build 阶段未配置");

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

  let taskContent: string;
  try {
    taskContent = await readFile(taskPath, "utf-8");
  } catch {
    throw new Error(`task.md not found in ${changeDir}`);
  }

  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 function assembleArchivePrompt(
  config: RuneConfig,
  changeName: string,
): string {
  const archive = config.stages.archive;
  if (!archive) throw new Error("archive 阶段未配置");

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