/**
 * Action: validate
 *
 * Validates a skill directory against the agentskills.io specification.
 *
 * Checks performed:
 *   1.  SKILL.md exists
 *   2.  YAML frontmatter delimiters (--- ... ---) are present
 *   3.  'name' field is present in frontmatter
 *   4.  'name' matches the directory name (basename)
 *   5.  'name' length ≤ 64 characters
 *   6.  'name' uses only a-z, 0-9, hyphens
 *   7.  'name' does not start with a hyphen
 *   8.  'name' does not end with a hyphen
 *   9.  'name' has no consecutive hyphens
 *   10. 'description' field is present and non-empty
 *   11. 'description' length ≤ 1024 characters
 *   12. SKILL.md body (lines after frontmatter) ≤ 500 lines (recommendation)
 *   13. If scripts/ exists, Taskfile.yml must be present inside it
 *
 * Output: YAML with success flag, counts, and per-check detail list.
 */

import { existsSync, readFileSync, readdirSync } from "node:fs";
import { join, basename } from "node:path";

// ---------------------------------------------------------------------------
// Types
// ---------------------------------------------------------------------------

interface CheckResult {
  id: number;
  pass: boolean;
  level: "error" | "warning" | "info";
  message: string;
}

interface DirectoryInfo {
  found: boolean;
  files?: number;
  "Taskfile.yml"?: boolean;
}

interface ValidateOutput {
  action: "validate";
  "skill-dir": string;
  success: boolean;
  summary: {
    passed: number;
    failed: number;
    warnings: number;
  };
  checks: CheckResult[];
  optional: {
    "scripts/": DirectoryInfo;
    "references/": DirectoryInfo;
    "assets/": DirectoryInfo;
  };
}

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

function countFilesSync(dir: string): number {
  try {
    const entries = readdirSync(dir, { withFileTypes: true });
    let count = 0;
    for (const e of entries) {
      if (e.isDirectory()) {
        count += countFilesSync(join(dir, e.name));
      } else {
        count++;
      }
    }
    return count;
  } catch {
    return 0;
  }
}

// ---------------------------------------------------------------------------
// Frontmatter parser — handles scalar and > block values
// ---------------------------------------------------------------------------

function parseFrontmatter(raw: string): Record<string, string> {
  const result: Record<string, string> = {};
  const lines = raw.split("\n");
  let i = 0;
  while (i < lines.length) {
    const line = lines[i];
    const keyMatch = line.match(/^([a-zA-Z_-]+)\s*:\s*(.*)/);
    if (keyMatch) {
      const key = keyMatch[1];
      const val = keyMatch[2].trim();
      if (val === ">" || val === "|") {
        // Multi-line block scalar — collect indented continuation lines
        const parts: string[] = [];
        i++;
        while (
          i < lines.length &&
          (lines[i].startsWith(" ") || lines[i].startsWith("\t") || lines[i].trim() === "")
        ) {
          parts.push(lines[i].trim());
          i++;
        }
        result[key] = parts.join(" ").trim();
        continue;
      } else {
        result[key] = val;
      }
    }
    i++;
  }
  return result;
}

// ---------------------------------------------------------------------------
// Optional directories inspector
// ---------------------------------------------------------------------------

function inspectOptional(skillDir: string): ValidateOutput["optional"] {
  function dirInfo(subdir: string): DirectoryInfo {
    const p = join(skillDir, subdir);
    if (!existsSync(p)) return { found: false };
    return { found: true, files: countFilesSync(p) };
  }

  const scriptsDir = join(skillDir, "scripts");
  const scriptsInfo = dirInfo("scripts");

  if (scriptsInfo.found) {
    scriptsInfo["Taskfile.yml"] = existsSync(join(scriptsDir, "Taskfile.yml"));
  }

  return {
    "scripts/": scriptsInfo,
    "references/": dirInfo("references"),
    "assets/": dirInfo("assets"),
  };
}

// ---------------------------------------------------------------------------
// Output builder
// ---------------------------------------------------------------------------

function buildOutput(
  skillDir: string,
  checks: CheckResult[],
  optional: ValidateOutput["optional"]
): Record<string, unknown> {
  const passed   = checks.filter((c) => c.pass).length;
  const failed   = checks.filter((c) => !c.pass && c.level === "error").length;
  const warnings = checks.filter((c) => !c.pass && c.level === "warning").length;

  return {
    action: "validate",
    "skill-dir": skillDir,
    success: failed === 0,
    summary: { passed, failed, warnings },
    checks,
    optional,
  };
}

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

export function run(options: Record<string, string | undefined>): Record<string, unknown> {
  const skillDir = options["skill-dir"];
  if (!skillDir) {
    return {
      action: "validate",
      success: false,
      error: "Missing required option: --skill-dir",
    };
  }

  const checks: CheckResult[] = [];
  let checkId = 1;

  const ok  = (message: string, level: CheckResult["level"] = "error"): CheckResult =>
    ({ id: checkId++, pass: true,  level, message });
  const err = (message: string, level: CheckResult["level"] = "error"): CheckResult =>
    ({ id: checkId++, pass: false, level, message });

  // ── Check 1: SKILL.md exists ─────────────────────────────────────────────
  const skillMdPath = join(skillDir, "SKILL.md");
  if (!existsSync(skillMdPath)) {
    checks.push(err("SKILL.md does not exist in skill directory"));
    return buildOutput(skillDir, checks, inspectOptional(skillDir));
  }
  checks.push(ok("SKILL.md exists"));

  const raw = readFileSync(skillMdPath, "utf-8");

  // ── Check 2: Frontmatter delimiters ──────────────────────────────────────
  const fmMatch = raw.match(/^---\r?\n([\s\S]*?)\r?\n---\r?\n([\s\S]*)$/);
  if (!fmMatch) {
    checks.push(err("YAML frontmatter delimiters (--- ... ---) not found"));
    return buildOutput(skillDir, checks, inspectOptional(skillDir));
  }
  checks.push(ok("YAML frontmatter delimiters found"));

  const fm   = parseFrontmatter(fmMatch[1]);
  const body = fmMatch[2];

  // ── Checks 3–9: name field ───────────────────────────────────────────────
  const name = fm["name"];
  if (!name) {
    checks.push(err("'name' field is missing from frontmatter"));
  } else {
    checks.push(ok(`'name' field is present: ${name}`));

    const dirName = basename(skillDir);
    checks.push(
      name === dirName
        ? ok("'name' matches directory name")
        : err(`'name' (${name}) does not match directory name (${dirName})`)
    );

    checks.push(
      name.length <= 64
        ? ok(`'name' length is ${name.length} (max 64)`)
        : err(`'name' length is ${name.length} (max 64)`)
    );

    checks.push(
      /[^a-z0-9-]/.test(name)
        ? err("'name' contains characters outside a-z, 0-9, hyphen")
        : ok("'name' uses only allowed characters (a-z, 0-9, -)")
    );

    checks.push(
      name.startsWith("-")
        ? err("'name' must not start with a hyphen")
        : ok("'name' does not start with a hyphen")
    );

    checks.push(
      name.endsWith("-")
        ? err("'name' must not end with a hyphen")
        : ok("'name' does not end with a hyphen")
    );

    checks.push(
      /--/.test(name)
        ? err("'name' contains consecutive hyphens")
        : ok("'name' has no consecutive hyphens")
    );
  }

  // ── Checks 10–11: description field ──────────────────────────────────────
  const description = fm["description"];
  if (!description || description.trim() === "") {
    checks.push(err("'description' field is missing or empty"));
  } else {
    const descLen = description.trim().length;
    checks.push(ok(`'description' is present (${descLen} chars)`));
    checks.push(
      descLen <= 1024
        ? ok(`'description' length is ${descLen} (max 1024)`)
        : err(`'description' length is ${descLen} (max 1024)`)
    );
  }

  // ── Check 12: Body line count ─────────────────────────────────────────────
  const bodyLines = body.split("\n").length;
  checks.push(
    bodyLines <= 500
      ? ok(`SKILL.md body is ${bodyLines} lines (max 500 recommended)`)
      : err(`SKILL.md body is ${bodyLines} lines (max 500 recommended)`, "warning")
  );

  // ── Check 13: scripts/ must have Taskfile.yml ─────────────────────────────
  const scriptsDir = join(skillDir, "scripts");
  if (existsSync(scriptsDir)) {
    checks.push(
      existsSync(join(scriptsDir, "Taskfile.yml"))
        ? ok("scripts/Taskfile.yml exists")
        : err("scripts/ exists but Taskfile.yml is missing — it is required")
    );
  }

  return buildOutput(skillDir, checks, inspectOptional(skillDir));
}