import { readFileSync, existsSync } from "node:fs";
import { resolve } from "node:path";
import { describe, it, expect } from "vitest";
import yaml from "js-yaml";

const SKILLS_ROOT = resolve(__dirname, "../skills");

interface SkillFrontmatter {
  name?: string;
  description?: string;
  "argument-hint"?: string;
  "user-invocable"?: boolean;
  [key: string]: unknown;
}

function parseSkillMd(skillDir: string): {
  frontmatter: SkillFrontmatter;
  body: string;
} {
  const filePath = resolve(SKILLS_ROOT, skillDir, "SKILL.md");
  const raw = readFileSync(filePath, "utf-8");
  const match = raw.match(/^---\n([\s\S]*?)\n---\n([\s\S]*)$/);
  if (!match) {
    throw new Error(`Invalid SKILL.md format in ${skillDir}: no frontmatter`);
  }
  return {
    frontmatter: yaml.load(match[1]) as SkillFrontmatter,
    body: match[2],
  };
}

const INTERACTIVE_SKILLS = [
  {
    dir: "estimate",
    mcpTool: "fathom_estimate_task_cost",
  },
  {
    dir: "recommend-model",
    mcpTool: "fathom_recommend_model",
  },
  {
    dir: "budget",
    mcpTool: "fathom_check_budget",
  },
  {
    dir: "status",
    mcpTool: "fathom_get_project_status",
  },
  {
    dir: "projections",
    mcpTool: "fathom_generate_tool_configs",
  },
  {
    dir: "gsd",
    mcpTool: "fathom_estimate_task_cost",
  },
];

const BACKGROUND_SKILLS = [
  {
    dir: "cost-preview",
    mcpTool: "fathom_estimate_task_cost",
  },
  {
    dir: "budget-warning",
    mcpTool: "fathom_check_budget",
  },
];

const ALL_SKILLS = [...INTERACTIVE_SKILLS, ...BACKGROUND_SKILLS];

for (const skill of INTERACTIVE_SKILLS) {
  describe(skill.dir, () => {
    const skillPath = resolve(SKILLS_ROOT, skill.dir, "SKILL.md");

    it("SKILL.md exists", () => {
      expect(existsSync(skillPath)).toBe(true);
    });

    it("has valid frontmatter with required fields", () => {
      const { frontmatter } = parseSkillMd(skill.dir);

      expect(frontmatter.name).toBeTypeOf("string");
      expect(frontmatter.name!.length).toBeGreaterThan(0);
      expect(frontmatter.description).toBeTypeOf("string");
      expect(frontmatter.description!.length).toBeGreaterThan(0);
      expect(frontmatter.description!.length).toBeLessThan(300);
    });

    it("is user-invocable (not false)", () => {
      const { frontmatter } = parseSkillMd(skill.dir);
      expect(frontmatter["user-invocable"]).not.toBe(false);
    });

    it("has argument-hint for interactive use", () => {
      const { frontmatter } = parseSkillMd(skill.dir);
      expect(frontmatter["argument-hint"]).toBeTypeOf("string");
    });

    it(`references MCP tool ${skill.mcpTool}`, () => {
      const { body } = parseSkillMd(skill.dir);
      expect(body).toContain(skill.mcpTool);
    });
  });
}

for (const skill of BACKGROUND_SKILLS) {
  describe(skill.dir, () => {
    const skillPath = resolve(SKILLS_ROOT, skill.dir, "SKILL.md");

    it("SKILL.md exists", () => {
      expect(existsSync(skillPath)).toBe(true);
    });

    it("has valid frontmatter with required fields", () => {
      const { frontmatter } = parseSkillMd(skill.dir);

      expect(frontmatter.name).toBeTypeOf("string");
      expect(frontmatter.name!.length).toBeGreaterThan(0);
      expect(frontmatter.description).toBeTypeOf("string");
      expect(frontmatter.description!.length).toBeGreaterThan(0);
      expect(frontmatter.description!.length).toBeLessThan(300);
    });

    it("user-invocable is exactly false", () => {
      const { frontmatter } = parseSkillMd(skill.dir);
      expect(frontmatter["user-invocable"]).toBe(false);
    });

    it(`references MCP tool ${skill.mcpTool}`, () => {
      const { body } = parseSkillMd(skill.dir);
      expect(body).toContain(skill.mcpTool);
    });
  });
}