/**
 * Action: next
 *
 * Computes the next branch name for any git repository following the convention:
 *
 *   X.Y.Z.Q/{TASK_MANAGEMENT_CODE}-{FEATURE_X}-{SEQ}
 *
 * - X.Y.Z.Q              — version, read from git tags ONLY (latest semver tag;
 *                          3-part tags get Q=0). No tags → hard error.
 * - TASK_MANAGEMENT_CODE — task/ticket identifier, e.g. IIAA-123 (--task-key)
 * - FEATURE_X            — kebab-case feature/focus topic (--topic)
 * - SEQ                  — zero-padded 3-digit sequence, auto-incremented by scanning
 *                          existing local + remote branches with the same prefix
 *
 * Repository-independent: operates on --repo-dir (default: current directory).
 *
 * Usage:
 *   branch-tools --action next --task-key IIAA-123 --topic api-cleanup [--repo-dir /path]
 */

import { execFileSync } from "node:child_process";
import { resolve } from "node:path";

// ---------------------------------------------------------------------------
// Helpers
// ---------------------------------------------------------------------------

const TAG_PATTERN = /^v?(\d+)\.(\d+)\.(\d+)(?:\.(\d+))?$/;

export function git(repoDir: string, args: string[]): string {
  return execFileSync("git", ["-C", repoDir, ...args], { encoding: "utf-8" }).trim();
}

export function detectVersion(repoDir: string): string | undefined {
  const tags = git(repoDir, ["tag", "--list", "--sort=-v:refname"])
    .split("\n")
    .map((t) => t.trim())
    .filter((t) => TAG_PATTERN.test(t));
  if (tags.length === 0) return undefined;
  const m = tags[0].match(TAG_PATTERN)!;
  return `${m[1]}.${m[2]}.${m[3]}.${m[4] ?? "0"}`;
}

export function detectBaseBranch(repoDir: string): string | undefined {
  for (const candidate of ["origin/test", "origin/main"]) {
    try {
      git(repoDir, ["show-ref", "--verify", "--quiet", `refs/remotes/${candidate}`]);
      return candidate;
    } catch {
      // not present — try next
    }
  }
  return undefined;
}

export function nextSequence(repoDir: string, prefix: string): string {
  const branches = git(repoDir, ["branch", "-a", "--format=%(refname:short)"])
    .split("\n")
    .map((b) => b.trim().replace(/^origin\//, ""));
  let max = 0;
  for (const branch of branches) {
    if (!branch.startsWith(`${prefix}-`)) continue;
    const seq = branch.slice(prefix.length + 1);
    if (/^\d+$/.test(seq)) max = Math.max(max, parseInt(seq, 10));
  }
  return String(max + 1).padStart(3, "0");
}

export function computeBranchName(
  options: Record<string, string | undefined>
): { branch?: string; error?: string; parts?: Record<string, string> } {
  const taskKey = options["task-key"];
  if (!taskKey) return { error: "Missing required option: --task-key (e.g. IIAA-123)" };
  if (!/^[A-Z][A-Z0-9]*-[A-Za-z0-9]+$/.test(taskKey)) {
    return { error: `'task-key' must look like PROJECT-ID (e.g. IIAA-123). Got: '${taskKey}'` };
  }

  const topic = options["topic"];
  if (!topic) return { error: "Missing required option: --topic (kebab-case feature topic)" };
  if (!/^[a-z0-9]+(-[a-z0-9]+)*$/.test(topic)) {
    return { error: `'topic' must be kebab-case (a-z, 0-9, single hyphens). Got: '${topic}'` };
  }

  const repoDir = resolve(options["repo-dir"] ?? process.cwd());
  try {
    git(repoDir, ["rev-parse", "--git-dir"]);
  } catch {
    return { error: `Not a git repository: ${repoDir}` };
  }

  const version = detectVersion(repoDir);
  if (!version) {
    return { error: `No version tag found in ${repoDir} — the version (X.Y.Z.Q) is read from git tags only. Create one first, e.g.: git tag 4.0.0.0` };
  }

  const prefix = `${version}/${taskKey}-${topic}`;
  const seq = nextSequence(repoDir, prefix);
  return {
    branch: `${prefix}-${seq}`,
    parts: { version, "task-key": taskKey, topic, seq },
  };
}

// ---------------------------------------------------------------------------
// Public API
// ---------------------------------------------------------------------------

export function run(options: Record<string, string | undefined>): Record<string, unknown> {
  const { branch, error, parts } = computeBranchName(options);
  if (error) return { action: "next", success: false, error };

  const repoDir = resolve(options["repo-dir"] ?? process.cwd());
  const base = detectBaseBranch(repoDir);
  return {
    action: "next",
    success: true,
    branch,
    "base-branch": base ?? "NONE — remote has neither test nor main; ask the user",
    ...parts ? { parts } : {},
  };
}