#!/usr/bin/env bun

/**
 * Initialize a new Claude skill from template or scratch
 *
 * Usage:
 *   bun run init-skill.ts <skill-name> <output-dir>
 *   bun run init-skill.ts <skill-name> <output-dir> --template <template-name>
 *
 * Templates: api-wrapper, document-processor, dev-workflow, research-synthesizer, simple
 */

import * as fs from "node:fs";
import { homedir } from "node:os";
import * as path from "node:path";

const SCRIPT_DIR = path.dirname(new URL(import.meta.url).pathname);
const TEMPLATES_DIR = path.join(SCRIPT_DIR, "../templates/skill-archetypes");

/**
 * Result of skill initialization.
 */
interface InitResult {
	/** Whether initialization succeeded or failed */
	status: "success" | "error";
	/** Path to created skill directory */
	skillDir?: string;
	/** Template used if any */
	template?: string;
	/** Files created during initialization */
	files?: string[];
	/** Suggested next steps after initialization */
	nextSteps?: string[];
	/** Error message if status is "error" */
	error?: string;
	/** Available templates when template not found */
	availableTemplates?: string[];
}

function getAvailableTemplates(): string[] {
	if (!fs.existsSync(TEMPLATES_DIR)) return [];
	return fs
		.readdirSync(TEMPLATES_DIR)
		.filter((f) => fs.statSync(path.join(TEMPLATES_DIR, f)).isDirectory());
}

function copyDir(src: string, dest: string): string[] {
	const copiedFiles: string[] = [];
	fs.mkdirSync(dest, { recursive: true });

	for (const entry of fs.readdirSync(src, { withFileTypes: true })) {
		// Prevent path traversal attacks
		if (entry.name.includes("..") || path.isAbsolute(entry.name)) {
			throw new Error(`Invalid file name: ${entry.name}`);
		}
		const srcPath = path.join(src, entry.name);
		// Rename SKILL.template.md to SKILL.md during copy
		const destName =
			entry.name === "SKILL.template.md" ? "SKILL.md" : entry.name;
		const destPath = path.join(dest, destName);

		if (entry.isDirectory()) {
			copiedFiles.push(...copyDir(srcPath, destPath));
		} else {
			fs.copyFileSync(srcPath, destPath);
			copiedFiles.push(path.relative(dest, destPath) || destName);
		}
	}

	return copiedFiles;
}

function toTitleCase(str: string): string {
	return str
		.split("-")
		.map((word) => word.charAt(0).toUpperCase() + word.slice(1))
		.join(" ");
}

function createMinimalSkill(skillName: string, outputDir: string): InitResult {
	const skillDir = path.join(outputDir, skillName);

	if (fs.existsSync(skillDir)) {
		return {
			status: "error",
			error: `Directory already exists: ${skillDir}`,
		};
	}

	fs.mkdirSync(skillDir, { recursive: true });

	const titleName = toTitleCase(skillName);
	const skillMd = `---
name: ${titleName}
description: TODO - Describe what this skill does and when to use it. Include trigger keywords users might mention.
---

# ${titleName}

## Quick Start

TODO: Fastest path to value (3-5 lines)

## Instructions

When this skill is activated:

1. **Step 1**
   - Detail

2. **Step 2**
   - Detail

## Examples

### Example 1: Basic Usage

\`\`\`
TODO: Add concrete example
\`\`\`

## Best Practices

- TODO: Add best practices

## Related Skills

- TODO: Add related skills if any
`;

	fs.writeFileSync(path.join(skillDir, "SKILL.md"), skillMd);

	return {
		status: "success",
		skillDir,
		files: ["SKILL.md"],
		nextSteps: [
			"Edit SKILL.md frontmatter - description is critical for discovery",
			"Replace all TODO placeholders with actual content",
			"Add examples that demonstrate real usage",
			"Run validate-claude-skill to check quality",
		],
	};
}

function createFromTemplate(
	skillName: string,
	outputDir: string,
	templateName: string,
): InitResult {
	const templateDir = path.join(TEMPLATES_DIR, templateName);
	const availableTemplates = getAvailableTemplates();

	if (!fs.existsSync(templateDir)) {
		return {
			status: "error",
			error: `Template '${templateName}' not found`,
			availableTemplates,
		};
	}

	const skillDir = path.join(outputDir, skillName);

	if (fs.existsSync(skillDir)) {
		return {
			status: "error",
			error: `Directory already exists: ${skillDir}`,
		};
	}

	const files = copyDir(templateDir, skillDir);

	// Make scripts executable
	const scriptsDir = path.join(skillDir, "scripts");
	if (fs.existsSync(scriptsDir)) {
		for (const script of fs.readdirSync(scriptsDir)) {
			const scriptPath = path.join(scriptsDir, script);
			fs.chmodSync(scriptPath, 0o755);
		}
	}

	return {
		status: "success",
		skillDir,
		template: templateName,
		files,
		nextSteps: [
			"Replace all {{PLACEHOLDERS}} in SKILL.md with actual values",
			"Update scripts/ with your specific logic",
			"Craft a strong description for discoverability",
			"Test with real inputs",
			"Run validate-claude-skill to check quality",
		],
	};
}

function showUsage(): void {
	const templates = getAvailableTemplates();
	console.log(
		JSON.stringify(
			{
				usage: "init-skill.ts <skill-name> <output-dir> [--template <name>]",
				examples: [
					"bun run init-skill.ts my-skill ~/.claude/skills",
					"bun run init-skill.ts github-api .claude/skills --template api-wrapper",
				],
				availableTemplates: templates,
				templateDescriptions: {
					"api-wrapper": "For wrapping external APIs (REST, GraphQL)",
					"document-processor":
						"For working with file formats (PDF, DOCX, etc)",
					"dev-workflow": "For automating development tasks (git, CI, etc)",
					"research-synthesizer": "For gathering and synthesizing information",
					simple: "Minimal skill without scripts",
				},
			},
			null,
			2,
		),
	);
}

// Main
const args = process.argv.slice(2);

if (args.length === 0 || args.includes("--help") || args.includes("-h")) {
	showUsage();
	process.exit(0);
}

const templateIdx = args.indexOf("--template");
let template: string | null = null;

if (templateIdx !== -1) {
	template = args[templateIdx + 1];
	args.splice(templateIdx, 2);
}

const [skillName, outputDir] = args;

if (!skillName || !outputDir) {
	showUsage();
	process.exit(1);
}

// Validate skill name (minimum 2 chars, kebab-case)
if (skillName.length < 2 || !/^[a-z][a-z0-9-]*[a-z0-9]$|^[a-z]{2}$/.test(skillName)) {
	console.log(
		JSON.stringify({
			status: "error",
			error:
				"Skill name must be kebab-case (lowercase with hyphens, min 2 chars)",
			examples: ["my-skill", "github-api", "pdf-processor", "ai"],
		}),
	);
	process.exit(1);
}

// Expand ~ to home directory
const expandedOutputDir = outputDir.replace(/^~/, homedir());

let result: InitResult;

if (template) {
	result = createFromTemplate(skillName, expandedOutputDir, template);
} else {
	result = createMinimalSkill(skillName, expandedOutputDir);
}

console.log(JSON.stringify(result, null, 2));
process.exit(result.status === "success" ? 0 : 1);