import { Buffer } from "node:buffer";
import { BACKGROUND_CONTEXT } from "@earendil-works/chord/context";
import type { Environment } from "@berry/api";

function variable(env: Environment, name: string): string | undefined {
  // windows spells its variables in any case
  return Object.entries(env.variables).find(([key]) =>
    env.platform === "win32" ? key.toUpperCase() === name : key === name
  )?.[1];
}

async function findCommand(env: Environment, command: string): Promise<string | undefined> {
  const windows = env.platform === "win32";
  const names = windows
    ? (variable(env, "PATHEXT") ?? ".EXE").split(";").filter(Boolean).map((ext) => command + ext)
    : [command];
  for (const dir of (variable(env, "PATH") ?? "").split(windows ? ";" : ":").filter(Boolean)) {
    for (const name of names) {
      const file = await env.joinPath([dir.replace(/^"(.*)"$/, "$1"), name], BACKGROUND_CONTEXT);
      if (!file.ok) continue;
      const info = await env.fileInfo(file.value, BACKGROUND_CONTEXT);
      if (info.ok && info.value.kind !== "directory") return file.value;
    }
  }
}

const commands = new Map<string, Promise<boolean>>();

/** Whether `command` is on the environment's PATH: asked once of each machine and PATH. */
export function hasCommand(env: Environment, command: string): Promise<boolean> {
  const key = JSON.stringify([
    env.id,
    env.cwd,
    env.platform,
    variable(env, "PATH"),
    variable(env, "PATHEXT"),
    command,
  ]);
  let found = commands.get(key);
  if (found === undefined) {
    found = findCommand(env, command).then((path) => path !== undefined);
    commands.set(key, found);
  }
  return found;
}

/** PowerShell on this machine, favoring PS7 even when only PS5 is on PATH. */
export async function powershellCommand(env: Environment, command: string): Promise<string[]> {
  let shell = await findCommand(env, "pwsh");
  for (
    const [root, parts] of [
      ["PROGRAMFILES", ["PowerShell", "7", "pwsh.exe"]],
      ["PROGRAMW6432", ["PowerShell", "7", "pwsh.exe"]],
    ] as const
  ) {
    if (shell !== undefined) break;
    const dir = variable(env, root);
    if (!dir) continue;
    const file = await env.joinPath([dir, ...parts], BACKGROUND_CONTEXT);
    if (!file.ok) continue;
    const info = await env.fileInfo(file.value, BACKGROUND_CONTEXT);
    if (info.ok && info.value.kind !== "directory") shell = file.value;
  }
  shell ??= await findCommand(env, "powershell");
  if (shell === undefined) {
    const root = variable(env, "SYSTEMROOT");
    if (root) {
      const file = await env.joinPath([
        root,
        "System32",
        "WindowsPowerShell",
        "v1.0",
        "powershell.exe",
      ], BACKGROUND_CONTEXT);
      if (file.ok) {
        const info = await env.fileInfo(file.value, BACKGROUND_CONTEXT);
        if (info.ok && info.value.kind !== "directory") shell = file.value;
      }
    }
  }
  if (shell === undefined) {
    throw new Error("PowerShell not found. Install PowerShell 7 or add it to PATH.");
  }
  // encoded commands survive windows argument quoting and PS5's legacy input encoding
  const script = [
    "[Console]::OutputEncoding = [System.Text.UTF8Encoding]::new($false)",
    "$OutputEncoding = [Console]::OutputEncoding",
    "$ProgressPreference = 'SilentlyContinue'",
    command,
    "if ($?) { exit 0 }; if ($LASTEXITCODE) { exit $LASTEXITCODE }; exit 1",
  ].join("\n");
  return [
    shell,
    "-NoLogo",
    "-NoProfile",
    "-NonInteractive",
    "-OutputFormat",
    "Text",
    "-EncodedCommand",
    Buffer.from(script, "utf16le").toString("base64"),
  ];
}