/**
 * Action: deploy
 *
 * Deploys a skill directory into the agent skill directories so compatible
 * agents (Claude Code, Cline, Copilot, Codex, …) can discover it.
 *
 * Default targets (always resolved to absolute paths):
 *   $HOME/.agents/skills/<skill-name>
 *   $HOME/.claude/skills/<skill-name>
 *
 * $HOME is the current user's home directory (e.g. /Users/<username> on macOS,
 * /home/<username> on Linux), resolved at runtime via os.homedir().
 *
 * Modes:
 *   symlink (default) — creates an absolute-path symlink to the skill source.
 *                       The source stays the single source of truth (e.g. a git repo).
 *   copy              — copies the skill directory (excluding node_modules/, dist/, .git/).
 *
 * Existing symlinks at the destination are replaced. Existing real directories
 * are only replaced when --force is given.
 *
 * Usage:
 *   skill-tools --action deploy --skill-dir /abs/path/to/skill [--mode symlink|copy] [--targets dir1,dir2] [--force]
 */

import {
  cpSync,
  existsSync,
  lstatSync,
  mkdirSync,
  readFileSync,
  realpathSync,
  rmSync,
  symlinkSync,
  unlinkSync,
} from "node:fs";
import { homedir } from "node:os";
import { basename, join, resolve } from "node:path";

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

const DEFAULT_TARGETS = [".agents/skills", ".claude/skills"];

const COPY_EXCLUDES = new Set(["node_modules", "dist", ".git"]);

function readSkillName(skillDir: string): string | undefined {
  const skillMdPath = join(skillDir, "SKILL.md");
  const content = readFileSync(skillMdPath, "utf-8");
  const match = content.match(/^---\n[\s\S]*?^name:\s*(\S+)\s*$/m);
  return match?.[1];
}

function safeRealpath(path: string): string {
  try {
    return realpathSync(path);
  } catch {
    return resolve(path);
  }
}

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

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

  const skillDir = resolve(rawSkillDir);
  if (!existsSync(skillDir)) {
    return {
      action: "deploy",
      success: false,
      error: `Skill directory does not exist: ${skillDir}`,
    };
  }
  if (!existsSync(join(skillDir, "SKILL.md"))) {
    return {
      action: "deploy",
      success: false,
      error: `Not a skill directory (missing SKILL.md): ${skillDir}`,
    };
  }

  const mode = options["mode"] ?? "symlink";
  if (mode !== "symlink" && mode !== "copy") {
    return {
      action: "deploy",
      success: false,
      error: `'mode' must be 'symlink' or 'copy'. Got: '${mode}'`,
    };
  }

  const force = options["force"] === "true";

  const skillName = readSkillName(skillDir) ?? basename(skillDir);
  const dirName = basename(skillDir);
  const warnings: string[] = [];
  if (skillName !== dirName) {
    warnings.push(
      `Frontmatter name '${skillName}' does not match directory name '${dirName}' — deploying as '${skillName}'`
    );
  }

  const targets = (
    options["targets"]
      ? options["targets"].split(",").map((t) => t.trim()).filter(Boolean)
      : DEFAULT_TARGETS.map((t) => join(homedir(), t))
  ).map((t) => resolve(t));

  const sourceReal = safeRealpath(skillDir);
  const deployments: Record<string, unknown>[] = [];
  let success = true;

  for (const targetDir of targets) {
    const destination = join(targetDir, skillName);

    try {
      mkdirSync(targetDir, { recursive: true });

      let existing: ReturnType<typeof lstatSync> | undefined;
      try {
        existing = lstatSync(destination);
      } catch {
        existing = undefined;
      }

      if (existing && !existing.isSymbolicLink() && safeRealpath(destination) === sourceReal) {
        deployments.push({
          target: destination,
          status: "skipped",
          reason: "Destination is the source directory itself",
        });
        continue;
      }

      if (existing) {
        if (existing.isSymbolicLink()) {
          unlinkSync(destination);
        } else if (force) {
          rmSync(destination, { recursive: true });
        } else {
          deployments.push({
            target: destination,
            status: "skipped",
            reason: "Destination exists and is not a symlink — pass --force to replace",
          });
          success = false;
          continue;
        }
      }

      if (mode === "symlink") {
        symlinkSync(skillDir, destination);
      } else {
        cpSync(skillDir, destination, {
          recursive: true,
          filter: (src) => !COPY_EXCLUDES.has(basename(src)),
        });
      }

      deployments.push({ target: destination, status: "deployed", mode });
    } catch (err) {
      deployments.push({
        target: destination,
        status: "failed",
        reason: err instanceof Error ? err.message : String(err),
      });
      success = false;
    }
  }

  const result: Record<string, unknown> = {
    action: "deploy",
    success,
    "skill-name": skillName,
    "skill-dir": skillDir,
    mode,
    deployments,
  };
  if (warnings.length > 0) {
    result["warnings"] = warnings;
  }
  return result;
}