import * as readline from "node:readline";
import { loadConfig } from "../config";
import { isGitRepo, getRepoRoot } from "../git";
import { collectProjectContext } from "../context";
import { PR_SYSTEM_PROMPT, buildPRPrompt } from "../prompt";
import { generatePRMessage } from "../ai";
import { BACK, SKIP_WAIT, selectOne } from "../menu";
import {
  getDefaultBranch,
  getBranchName,
  getBranchPushStatus,
  pushCurrentBranch,
  getBranchCommits,
  getBranchDiff,
  detectPlatform,
  getRemoteHostname,
  createPR,
} from "../pr";
import type { Platform } from "../pr";
import { BOLD, GREEN, YELLOW, CYAN, RED, DIM, RESET } from "../terminal";
import { isStdinTTY } from "../tty";
import { copyToClipboard } from "../clipboard";
import type { ParsedArgs } from "../cli";

function ask(question: string): Promise<string> {
  const rl = readline.createInterface({ input: process.stdin, output: process.stdout });
  return new Promise((resolve) => {
    rl.question(question, (answer) => {
      rl.close();
      resolve(answer.trim());
    });
  });
}

async function selectPlatform(hostname: string): Promise<Platform | null | typeof BACK> {
  if (!isStdinTTY()) {
    console.error(`\n  ${RED()}Error: Platform selection requires a TTY.${RESET()}\n`);
    process.exit(1);
  }
  return selectOne({
    title: "Select remote platform",
    subtitle: `Remote ${hostname} could not be auto-detected`,
    items: [
      { label: "GitHub", value: "github" as Platform, description: "Use gh CLI" },
      { label: "Gitea", value: "gitea" as Platform, description: "Use tea CLI" },
      { label: "GitLab", value: "gitlab" as Platform, description: "Use glab CLI" },
    ],
  });
}

export async function handlePR(args: ParsedArgs): Promise<number> {
  const config = await loadConfig();

  if (!config.apiKey) {
    console.error(`\n  ${RED()}Error: API key not set. Run ${BOLD()}gai config${RESET()}${RED()} to configure.${RESET()}\n`);
    return 1;
  }

  if (!(await isGitRepo())) {
    console.error(`\n  ${RED()}Error: Not a git repository.${RESET()}\n`);
    return 1;
  }

  const draft = args.flags["draft"] as boolean;
  const verbose = args.flags["verbose"] as boolean;

  let platform = await detectPlatform();
  if (!platform) {
    const hostname = (await getRemoteHostname()) || "unknown";
    const chosen = await selectPlatform(hostname);
    if (chosen === BACK) return SKIP_WAIT as unknown as number;
    if (!chosen) {
      console.log("  Aborted.");
      return 0;
    }
    platform = chosen;
  }

  const platformLabel = platform === "github" ? "GitHub" : platform === "gitlab" ? "GitLab" : "Gitea";
  console.log(`  Using: ${CYAN()}${platformLabel}${RESET()}`);

  const baseBranch = await getDefaultBranch();
  const branchName = await getBranchName();

  if (branchName === baseBranch) {
    console.error(`\n  ${RED()}Error: You are on the default branch (${baseBranch}). Switch to a feature branch first.${RESET()}\n`);
    return 1;
  }

  console.log(`  Branch: ${CYAN()}${branchName}${RESET()} → base: ${CYAN()}${baseBranch}${RESET()}`);

  const commits = await getBranchCommits(baseBranch);

  if (commits.length === 0) {
    const choice = await selectOne({
      title: "No commits to compare",
      subtitle: `No commits on ${branchName} compared to ${baseBranch}. Commit something first.`,
      items: [{ label: "Back", value: "back" as const }],
    });
    if (choice === null) process.exit(0);
    return SKIP_WAIT as unknown as number;
  }

  console.log(`  ${commits.length} commit${commits.length > 1 ? "s" : ""} on this branch`);

  if (verbose) {
    console.log(`  ${DIM()}Model: ${config.model} | API: ${config.apiBase}${RESET()}`);
  }

  const pushStatus = await getBranchPushStatus();
  if (!pushStatus.pushed) {
    const target = pushStatus.upstream ?? `origin/${branchName}`;
    const answer = await ask(
      `  Branch is not pushed to ${CYAN()}${target}${RESET()}. Push now? [${GREEN()}Y${RESET()}/n] `,
    );

    if (answer.toLowerCase() === "n") {
      console.log("  Aborted.");
      return 0;
    }

    console.log(`  Pushing ${CYAN()}${branchName}${RESET()}...`);
    try {
      await pushCurrentBranch(branchName, pushStatus.upstream);
      console.log(`  ${GREEN()}Pushed ${branchName}.${RESET()}`);
    } catch (err) {
      console.error(`\n  ${RED()}Push failed: ${err instanceof Error ? err.message : err}${RESET()}\n`);
      return 1;
    }
  }

  const diff = await getBranchDiff(baseBranch);
  if (!diff) {
    console.error(`\n  ${RED()}Error: No diff from base branch.${RESET()}\n`);
    return 1;
  }

  const MAX_DIFF_SIZE = 15000;
  const truncatedDiff = diff.length > MAX_DIFF_SIZE
    ? diff.substring(0, MAX_DIFF_SIZE) + "\n... (truncated)"
    : diff;

  const repoRoot = await getRepoRoot();
  const projectCtx = await collectProjectContext(repoRoot);

  const userPrompt = buildPRPrompt({
    readme: projectCtx.readme,
    packageDescription: projectCtx.packageDescription,
    structure: projectCtx.structure,
    branchName,
    baseBranch,
    branchCommits: commits,
    diff: truncatedDiff,
  });

  console.log("\n  Generating PR title and description...");

  let title: string;
  let body: string;
  try {
    const result = await generatePRMessage(config, PR_SYSTEM_PROMPT, userPrompt);
    title = result.title;
    body = result.body;
  } catch (err) {
    console.error(`\n  ${RED()}AI request failed: ${err instanceof Error ? err.message : err}${RESET()}\n`);
    return 1;
  }

  console.log(`\n  ${BOLD()}Generated PR:${RESET()}`);
  console.log(`    Title: ${GREEN()}${title}${RESET()}`);
  if (body) {
    console.log(`    Body:  ${DIM()}${body.replace(/\n/g, "\n           ")}${RESET()}`);
  }
  console.log("");

  const answer = await ask(`  Create this PR? [${GREEN()}Y${RESET()}/n/e] `);
  const lower = answer.toLowerCase();

  if (lower === "n") {
    console.log("  Aborted.");
    await copyToClipboard(`${title}\n\n${body}`);
    console.log(`  ${DIM()}PR title copied to clipboard.${RESET()}`);
    return 0;
  }

  if (lower === "e") {
    const newTitle = await ask("  Title: ");
    const newBody = await ask("  Body (optional): ");
    if (!newTitle.trim()) {
      console.log("  Aborted.");
      return 0;
    }
    title = newTitle;
    body = newBody;
  }

  console.log(`\n  Creating PR...`);

  try {
    const url = await createPR(platform, title, body, baseBranch, draft);
    console.log(`\n  ${GREEN()}${BOLD()}✔ PR created!${RESET()}`);
    console.log(`    ${CYAN()}${url}${RESET()}`);
  } catch (err) {
    console.error(`\n  ${RED()}PR creation failed: ${err instanceof Error ? err.message : err}${RESET()}\n`);
    return 1;
  }

  return 0;
}