import { existsSync, lstatSync, readlinkSync, renameSync, unlinkSync } from "node:fs";
import { resolve } from "node:path";
import { paths, platform } from "../hooks/lib/paths";
import { readJson, writeJson } from "../targets/lib";

/** Something an older PAL wrote that the current one neither writes nor reads. */
export interface Leftover {
  id: string;
  description: string;
  find(): string[];
  remove(): void;
}

type Json = Record<string, unknown>;

const claudeSettings = () => resolve(platform.claudeDir(), "settings.json");
const palSettings = () => resolve(paths.memory(), "pal-settings.json");

function isPathScopedFileToolRule(rule: string): boolean {
  return /^(?:Grep|Glob)\(/.test(rule);
}

function claudeAllowRules(): string[] {
  const settings = readJson<Json>(claudeSettings(), {});
  const allow = (settings.permissions as { allow?: unknown } | undefined)?.allow;
  return Array.isArray(allow)
    ? allow.filter((r): r is string => typeof r === "string")
    : [];
}

const claudeFileToolRules: Leftover = {
  id: "claude-file-tool-rules",
  description:
    "Remove Grep()/Glob() allow rules older templates wrote — Claude Code ignores them and warns on every prompt",
  find: () => claudeAllowRules().filter(isPathScopedFileToolRule),
  remove() {
    const settings = readJson<Json>(claudeSettings(), {});
    const permissions = settings.permissions as { allow: string[] };
    permissions.allow = permissions.allow.filter(
      (rule) => !isPathScopedFileToolRule(rule)
    );
    writeJson(claudeSettings(), settings);
  },
};

function startupFiles(): string[] {
  const settings = readJson<Json>(palSettings(), {});
  const files = (settings.loadAtStartup as { files?: unknown } | undefined)?.files;
  return Array.isArray(files)
    ? files.filter((f): f is string => typeof f === "string")
    : [];
}

const isProjectsFile = (file: string) => file.endsWith("PROJECTS.md");

const startupProjectsFile: Leftover = {
  id: "startup-projects-md",
  description:
    "Stop loading PROJECTS.md at startup — projects moved to the project store",
  find: () => startupFiles().filter(isProjectsFile),
  remove() {
    const settings = readJson<Json>(palSettings(), {});
    const startup = settings.loadAtStartup as { files: string[] };
    startup.files = startup.files.filter((file) => !isProjectsFile(file));
    writeJson(palSettings(), settings);
  },
};

const oldOpencodePlugin = () =>
  resolve(platform.opencodeDir(), "plugins", "pai-plugin.ts");

const opencodePluginOldName: Leftover = {
  id: "opencode-pai-plugin",
  description: "Remove the opencode plugin under its old name, pai-plugin.ts",
  find: () => (existsSync(oldOpencodePlugin()) ? [oldOpencodePlugin()] : []),
  remove: () => unlinkSync(oldOpencodePlugin()),
};

const oldCopilotInstructions = () =>
  resolve(platform.copilotDir(), "copilot-instructions.md");

function linksToAgentsMd(path: string): boolean {
  try {
    return lstatSync(path).isSymbolicLink() && readlinkSync(path).includes("AGENTS.md");
  } catch {
    return false;
  }
}

const copilotInstructionsLink: Leftover = {
  id: "copilot-instructions-link",
  description:
    "Remove the copilot-instructions.md link to AGENTS.md — Copilot now reads PAL's own instruction files",
  find: () =>
    linksToAgentsMd(oldCopilotInstructions()) ? [oldCopilotInstructions()] : [],
  remove: () => unlinkSync(oldCopilotInstructions()),
};

const debugLog = () => resolve(paths.debug(), "debug.log");

const debugLogPrev: Leftover = {
  id: "debug-log-prev",
  description: "Rename the old single rotated debug log, debug.log.prev, to debug.log.1",
  find: () => (existsSync(`${debugLog()}.prev`) ? [`${debugLog()}.prev`] : []),
  remove() {
    const prev = `${debugLog()}.prev`;
    if (existsSync(`${debugLog()}.1`)) unlinkSync(prev);
    else renameSync(prev, `${debugLog()}.1`);
  },
};

export const LEFTOVERS: Leftover[] = [
  claudeFileToolRules,
  startupProjectsFile,
  opencodePluginOldName,
  copilotInstructionsLink,
  debugLogPrev,
];