import { loadConfig } from "../config";
import {
  isGitRepo,
  getStagedFiles,
  getStagedDiff,
  getUnstagedFiles,
  getRepoRoot,
  applyFileSelection,
} from "../git";
import { selectFiles } from "../selector";
import { BACK, SKIP_WAIT } from "../menu";
import { collectProjectContext } from "../context";
import { REVIEW_SYSTEM_PROMPT, buildReviewPrompt } from "../prompt";
import { callAI } from "../ai";
import { BOLD, GREEN, YELLOW, RED, DIM, RESET, CYAN } from "../terminal";
import { isStdinTTY } from "../tty";
import type { StreamCallbacks } from "../types";
import type { ParsedArgs } from "../cli";

export async function handleReview(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;
  }

  const strictnessFlag = args.flags["strict"] as boolean
    ? "strict"
    : args.flags["lenient"] as boolean
      ? "lenient"
      : "normal";

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

  let diff: string;
  let sourceLabel: string;

  if (unstaged) {
    if (!(await isGitRepo())) {
      console.error(`\n  ${RED()}Error: Not a git repository.${RESET()}\n`);
      return 1;
    }
    try {
      diff = (await Bun.$`git diff`.quiet().text()).trim();
    } catch {
      diff = "";
    }
    sourceLabel = "unstaged changes";
  } else if (!isStdinTTY()) {
    const chunks: Buffer[] = [];
    for await (const chunk of process.stdin) {
      chunks.push(typeof chunk === "string" ? Buffer.from(chunk) : chunk);
    }
    diff = Buffer.concat(chunks).toString("utf-8").trim();
    sourceLabel = "piped input";
  } else {
    if (!(await isGitRepo())) {
      console.error(`\n  ${RED()}Error: Not a git repository.${RESET()}\n`);
      return 1;
    }
    const stagedFiles = await getStagedFiles();
    const unstagedFiles = await getUnstagedFiles();
    sourceLabel = "selected changes";

    if (stagedFiles.length > 0 || unstagedFiles.length > 0) {
      const selected = await selectFiles(stagedFiles, unstagedFiles);
      if (selected === BACK) return SKIP_WAIT as unknown as number;
      await applyFileSelection(stagedFiles, unstagedFiles, selected);
    }
    diff = await getStagedDiff();
  }

  if (!diff) {
    console.log(`  ${DIM()}No ${sourceLabel} to review.${RESET()}`);
    return 0;
  }

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

  let contextPrefix = "";
  try {
    if (await isGitRepo()) {
      const repoRoot = await getRepoRoot();
      const ctx = await collectProjectContext(repoRoot);
      if (ctx.packageDescription) {
        contextPrefix = `Project: ${ctx.packageDescription}\n\n`;
      }
    }
  } catch {}

  const userPrompt = contextPrefix + buildReviewPrompt(truncatedDiff, strictnessFlag);

  const strictnessLabel = strictnessFlag === "strict"
    ? `${RED()}strict${RESET()}`
    : strictnessFlag === "lenient"
      ? `${GREEN()}lenient${RESET()}`
      : `${YELLOW()}normal${RESET()}`;

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

  const tty = isStdinTTY();
  if (tty) {
    console.log(`\n  ${BOLD()}${CYAN()}Reviewing ${sourceLabel} (${strictnessLabel})...${RESET()}\n`);
  }

  try {
    const callbacks: StreamCallbacks | undefined = tty ? {
      onToken: (token) => process.stdout.write(token),
    } : undefined;

    const result = await callAI(config, REVIEW_SYSTEM_PROMPT, userPrompt, callbacks);
    if (callbacks) {
      process.stdout.write("\n");
    } else {
      process.stdout.write(result + "\n");
    }
  } catch (err) {
    console.error(`\n  ${RED()}AI request failed: ${err instanceof Error ? err.message : err}${RESET()}\n`);
    return 1;
  }

  return 0;
}