import { existsSync } from "node:fs";
import { homedir } from "node:os";
import path from "node:path";
import { parseArgs } from "node:util";
import { $, Glob } from "bun";
import chalk from "chalk";
import pkg from "../package.json" assert { type: "json" };

interface ScriptData {
  name: string;
  description: string;
  absolutePath: string;
}

class CLIError extends Error {
  name = "CLIError";

  constructor(message: string) {
    super(`rundir error: ${message}`);
  }
}

const TEMPLATE_FILE_PATH = process.env["RUNDIR_TEMPLATE"] ?? null;
const DEFAULT_TEMPLATE = `
#!/usr/bin/env bash
# Description...
`.trim();
const VERSION = pkg.version;
const RUNDIR_PATH = path.join(process.cwd(), ".run");
const COMMENT_STARTERS = ["#", "//", "--"];
const COMMANDS = ["ls", "help", "new", "create", "which", "x", "run"] as const;
type Command = (typeof COMMANDS)[number];

/**
 * Given an unknown string, parse a valid command or throw
 *
 * @param command The command to parse
 * @returns The parsed command
 */
function parseCommand(command: string): Command {
  if (COMMANDS.includes(command as Command)) {
    return command as Command;
  }

  throw new CLIError(`Unknown command: ${command}`);
}

/**
 * Fund a rundir, checking the current or provided directory
 * path and walking up the tree if no dir is found
 *
 * @param fromPath The path to start searching from
 * @returns The path to the rundir, or null if not found
 */
function findNearestRundir(fromPath?: string): string | null {
  const currentDir = fromPath ?? process.cwd();
  const potentialPath = path.join(currentDir, ".run");

  if (currentDir === path.dirname(currentDir)) {
    return null;
  }

  if (existsSync(potentialPath)) {
    return potentialPath;
  }

  return findNearestRundir(path.dirname(currentDir));
}

/**
 * Given the name of a script, return the absolute path to the script
 *
 * @param name The name of the script
 * @returns The absolute path to the script
 */
function makeScriptPath(name: string): string {
  const rundir = findNearestRundir();

  if (!rundir) {
    throw new CLIError("No rundir found in the current directory tree.");
  }

  return path.join(rundir, name);
}

/**
 * Given the name of a script, search for the script in the rundir and
 * return the absolute path to the script.
 * Searches the current directory's `.run` directory first, then works
 * up the directory tree until it reaches the home directory.
 *
 * If the script is not found, returns `null`.
 *
 * @param name The name of the script to find the path of
 */
async function findScriptPath(name: string): Promise<string | null> {
  let currentDir = process.cwd();

  while (currentDir !== path.dirname(currentDir)) {
    const potentialPath = path.join(currentDir, ".run", name);
    if (await Bun.file(potentialPath).exists()) {
      return potentialPath;
    }
    currentDir = path.dirname(currentDir);
  }

  const homeDirPath = path.join(homedir(), ".run", name);
  if (await Bun.file(homeDirPath).exists()) {
    return homeDirPath;
  }

  return null;
}

/**
 * Parses a line of text and returns the comment line or null
 * if the line does not start with a comment starter
 *
 * @param line The line of text to parse
 * @returns The comment line or null
 */
function getCommentLine(line: string): string | null {
  for (const starter of COMMENT_STARTERS) {
    if (line.startsWith(starter)) {
      return line.replace(starter, "").trim();
    }
  }

  return null;
}

/**
 * Given a script name, read the script file and return
 *
 * @param scriptName The name of the script to read
 * @returns The script data
 */
async function readScriptData(scriptName: string): Promise<ScriptData> {
  const scriptPath = await findScriptPath(scriptName);

  if (!scriptPath) {
    throw new CLIError(
      `Script "${scriptName}" not found in any rundir in the directory tree.`,
    );
  }

  const scriptFile = Bun.file(scriptPath);
  const scriptContent = await scriptFile.text();
  const [_, ...lines] = scriptContent.split("\n");

  const descriptionLines: string[] = [];

  for (const line of lines) {
    const commentLine = getCommentLine(line);
    if (!commentLine) {
      break;
    }

    descriptionLines.push(commentLine);
  }

  const description =
    descriptionLines.length > 0
      ? descriptionLines.join(" ")
      : "No description provided";

  return {
    absolutePath: scriptPath,
    name: path.basename(scriptPath),
    description: description.trim(),
  };
}

/**
 * List the scripts in the rundir or the path to a script if provided
 * @command
 */
async function ls(scriptName?: string) {
  if (scriptName) {
    const pathname = await findScriptPath(scriptName);
    if (pathname === null) {
      throw new CLIError(`Script "${scriptName}" not found.`);
    }

    console.log(pathname);
    return;
  }

  const currentRundir = findNearestRundir();
  const filesInDir = new Glob(`${currentRundir}/*`).scan();
  const scriptLines: string[] = [];

  for await (const file of filesInDir) {
    const scriptName = path.basename(file);
    const scriptData = await readScriptData(scriptName);
    scriptLines.push(
      `${chalk.dim("$")} ${scriptName} ${chalk.dim(`- ${scriptData.description}`)}`,
    );
  }

  const sorted = scriptLines.sort((a, b) => a.localeCompare(b));

  console.log(chalk.dim(currentRundir));
  console.log(sorted.join("\n"));
}

/**
 * Prints the absolute path of the rundir
 * @command
 */
async function which() {
  const nearest = findNearestRundir();

  if (!nearest) {
    console.error("No rundir found in the current directory tree.");
    process.exit(1);
  }

  console.log(path.resolve(nearest));
}

/**
 * Create a new script in the rundir
 * @command
 */
async function newScript(name: string) {
  const scriptPath = makeScriptPath(name);
  const scriptFile = Bun.file(scriptPath);
  let template = DEFAULT_TEMPLATE;

  if (await scriptFile.exists()) {
    throw new CLIError(`Script "${name}" already exists.`);
  }

  if (TEMPLATE_FILE_PATH) {
    const templateFile = Bun.file(TEMPLATE_FILE_PATH);
    if (await templateFile.exists()) {
      template = await templateFile.text();
    } else {
      console.warn(
        chalk.yellow(`Warn: Template "${TEMPLATE_FILE_PATH}" not found`),
      );
    }
  }

  await Bun.write(scriptFile, template);
  await $`chmod +x ${scriptPath}`;
  console.log(name);
}

/**
 * Executes a script from the rundir
 * @command
 */
async function runScript(name: string) {
  const scriptPath = await findScriptPath(name);

  if (!scriptPath) {
    console.error(`Script "${name}" not found.`);
    process.exit(1);
  }

  await $`${scriptPath}`;
}

/**
 * Prints the help message
 * @command
 */
async function help() {
  console.log(
    `
rundir ${VERSION}
Usage: rundir [command]

Commands:
  x <name>    Run a script from the nearest rundir (alias: run)
  new <name>  Create a new script in the rundir (alias: create)
  ls          List all scripts in the rundir
  ls <name>   Print the absolute path to a specific script
  which       Print the absolute path of the rundir
  help        Show this help message
`.trim(),
  );
}

/**
 * Parses the command line arguments and returns the positionals
 * @returns The positional arguments for the command
 */
function readArgs(): string[] {
  const { positionals } = parseArgs({
    args: Bun.argv,
    allowPositionals: true,
    strict: true,
  });

  return positionals.slice(2);
}

type Handler = (...args: string[]) => void | Promise<void>;
type HandlerDescriptor = [number, Handler];
const COMMAND_HANDLERS: Record<Command, HandlerDescriptor> = {
  ls: [0, ls],
  help: [0, help],
  which: [0, which],
  new: [1, newScript],
  create: [1, newScript],
  x: [1, runScript],
  run: [1, runScript],
};

async function main() {
  const [rawCommand, ...params] = readArgs();

  // No arguments provided - list scripts
  if (rawCommand === undefined) {
    return ls();
  }

  const command = parseCommand(rawCommand);
  const [requiredArgs, handler] = COMMAND_HANDLERS[command];

  if (params.length < requiredArgs) {
    throw new CLIError(`Missing required arguments for command "${command}"`);
  }

  return handler(...params);
}

try {
  await main();
} catch (e) {
  if (e instanceof CLIError) {
    console.error(chalk.red(e.message));
    process.exit(0);
  }

  console.error(chalk.red("An unexpected error occurred:"));
  console.error(e);
  process.exit(0);
}