import { accessSync, constants, statSync } from "node:fs";
import { extname, join, resolve } from "node:path";

export interface CommandLookupOptions {
  platform?: NodeJS.Platform;
  path?: string;
  pathExt?: string;
  cwd?: string;
}

/** Absolute path of `cmd` on PATH, or null when it is not installed. */
export function findCommand(cmd: string, options: CommandLookupOptions = {}): string | null {
  const platform = options.platform ?? process.platform;
  const pathValue = options.path ?? process.env.PATH ?? "";
  const pathEntries = pathValue.split(platform === "win32" ? ";" : ":");
  const searchDirectories = platform === "win32"
    ? [options.cwd ?? process.cwd(), ...pathEntries]
    : pathEntries;
  const extensions = platform === "win32" && !extname(cmd)
    ? (options.pathExt ?? process.env.PATHEXT ?? ".COM;.EXE;.BAT;.CMD").split(";").filter(Boolean)
    : [""];
  const accessMode = platform === "win32" ? constants.F_OK : constants.X_OK;

  for (const rawDirectory of searchDirectories) {
    const directory = platform === "win32" && rawDirectory.startsWith('"') && rawDirectory.endsWith('"')
      ? rawDirectory.slice(1, -1)
      : rawDirectory;
    for (const extension of extensions) {
      try {
        const candidate = resolve(options.cwd ?? process.cwd(), directory || ".", `${cmd}${extension}`);
        accessSync(candidate, accessMode);
        if (statSync(candidate).isFile()) return candidate;
      } catch {
        // Continue searching PATH.
      }
    }
  }

  return null;
}

export function hasCommand(cmd: string, options: CommandLookupOptions = {}): boolean {
  return findCommand(cmd, options) !== null;
}

export const REQUIRED_COMMANDS = ["bat", "delta", "glow"] as const;
export type RequiredCommand = (typeof REQUIRED_COMMANDS)[number];

const HOMEBREW_PACKAGES: Record<RequiredCommand, string> = { bat: "bat", delta: "git-delta", glow: "glow" };
const INSTALL_DOCS_URL = "https://github.com/tmustier/pi-extensions/tree/main/files-widget#install";

export function missingCommandsMessage(missing: readonly RequiredCommand[], platform: NodeJS.Platform = process.platform): string {
  const install = platform === "darwin"
    ? `Install: brew install ${missing.map((command) => HOMEBREW_PACKAGES[command]).join(" ")}`
    : `Install with your package manager: ${INSTALL_DOCS_URL}`;
  return `files-widget requires ${missing.join(", ")}. ${install}`;
}

export function isUntrackedStatus(status?: string): boolean {
  return status === "?" || status === "??";
}

export function isMarkdownPath(path: string): boolean {
  return path.toLowerCase().endsWith(".md");
}

export function stripLeadingEmptyLines(lines: string[]): string[] {
  let startIdx = 0;
  while (startIdx < lines.length && !lines[startIdx].trim()) {
    startIdx++;
  }
  return lines.slice(startIdx);
}