"""Skills system — load markdown skill files at runtime.

Inspired by Claude Code's Skill system. Each skill is a directory with:
- SKILL.md: the skill instructions (markdown with YAML frontmatter)
- references/ (optional): supporting docs
- scripts/ (optional): helper scripts

Skills are discovered under code/skills/builtins/ and can also be loaded
from the workspace's .sonicoder/skills/ directory.
"""

from __future__ import annotations

import logging
import os
import re
from pathlib import Path
from typing import Any

logger = logging.getLogger(__name__)

# ─── Skill discovery roots ──────────────────────────────────────────────

_BUILTIN_SKILLS_DIR = os.path.join(os.path.dirname(__file__), "builtins")
_USER_SKILLS_DIRNAME = ".sonicoder/skills"  # relative to workspace root


def _skill_dirs() -> list[str]:
    """Return all directories to search for skills."""
    dirs = [_BUILTIN_SKILLS_DIR]
    # Add user skills dir from workspace
    try:
        from code.tools.fs import get_workspace_root
        user_dir = os.path.join(get_workspace_root(), _USER_SKILLS_DIRNAME)
        if os.path.isdir(user_dir):
            dirs.append(user_dir)
    except Exception:
        pass
    return dirs


# ─── YAML frontmatter parsing ───────────────────────────────────────────

_FRONTMATTER_RE = re.compile(r"^---\s*\n(.*?)\n---\s*\n(.*)$", re.DOTALL)


def _parse_frontmatter(content: str) -> tuple[dict[str, str], str]:
    """Parse YAML frontmatter from markdown. Returns (metadata, body)."""
    match = _FRONTMATTER_RE.match(content)
    if not match:
        return {}, content

    raw_yaml = match.group(1)
    body = match.group(2)

    # Very simple YAML parser (key: value pairs only)
    meta: dict[str, str] = {}
    for line in raw_yaml.splitlines():
        line = line.strip()
        if not line or line.startswith("#"):
            continue
        if ":" in line:
            key, _, value = line.partition(":")
            meta[key.strip()] = value.strip().strip("\"'")
    return meta, body


# ─── Skill loading ──────────────────────────────────────────────────────

def _load_skill(skill_dir: str) -> dict[str, Any] | None:
    """Load a single skill from a directory."""
    skill_md = os.path.join(skill_dir, "SKILL.md")
    if not os.path.isfile(skill_md):
        return None

    try:
        with open(skill_md, "r", encoding="utf-8") as f:
            content = f.read()
    except Exception as exc:
        logger.warning("Failed to read %s: %s", skill_md, exc)
        return None

    meta, body = _parse_frontmatter(content)

    # Load any reference files
    references: dict[str, str] = {}
    refs_dir = os.path.join(skill_dir, "references")
    if os.path.isdir(refs_dir):
        for fname in os.listdir(refs_dir):
            if fname.endswith((".md", ".txt")):
                try:
                    with open(os.path.join(refs_dir, fname), "r", encoding="utf-8") as f:
                        references[fname] = f.read()
                except Exception:
                    pass

    return {
        "name": meta.get("name", os.path.basename(skill_dir)),
        "description": meta.get("description", ""),
        "language": meta.get("language", ""),
        "tags": [t.strip() for t in meta.get("tags", "").split(",") if t.strip()],
        "body": body.strip(),
        "references": references,
        "path": skill_dir,
    }


def list_skills() -> list[dict[str, Any]]:
    """List all available skills (metadata only, no body)."""
    skills: list[dict[str, Any]] = []
    seen_names: set[str] = set()

    for skills_dir in _skill_dirs():
        if not os.path.isdir(skills_dir):
            continue
        for entry in sorted(os.listdir(skills_dir)):
            entry_path = os.path.join(skills_dir, entry)
            if not os.path.isdir(entry_path):
                continue
            skill = _load_skill(entry_path)
            if skill and skill["name"] not in seen_names:
                seen_names.add(skill["name"])
                skills.append({
                    "name": skill["name"],
                    "description": skill["description"],
                    "language": skill["language"],
                    "tags": skill["tags"],
                })
    return skills


def get_skill(name: str) -> dict[str, Any] | None:
    """Get full skill content by name."""
    for skills_dir in _skill_dirs():
        if not os.path.isdir(skills_dir):
            continue
        # Try directory match
        for entry in os.listdir(skills_dir):
            entry_path = os.path.join(skills_dir, entry)
            if not os.path.isdir(entry_path):
                continue
            skill = _load_skill(entry_path)
            if skill and skill["name"] == name:
                return skill
    return None


def invoke_skill(name: str) -> dict[str, Any]:
    """Invoke a skill by name — returns its full body and references."""
    skill = get_skill(name)
    if not skill:
        return {
            "success": False,
            "error": f"Skill not found: {name}",
            "available": [s["name"] for s in list_skills()],
        }
    return {
        "success": True,
        "name": skill["name"],
        "description": skill["description"],
        "body": skill["body"],
        "references": skill["references"],
    }


def build_skills_context(skill_names: list[str] | None = None) -> str:
    """Build a context string with skill bodies to inject into the prompt.

    If skill_names is None, includes all skills (brief listing only).
    """
    if not skill_names:
        # List all skills briefly
        skills = list_skills()
        if not skills:
            return ""
        lines = ["Available skills (use /skill <name> to load full instructions):"]
        for s in skills:
            desc = s["description"][:120]
            lines.append(f"- {s['name']}: {desc}")
        return "\n".join(lines)

    # Load full bodies for requested skills
    parts: list[str] = []
    for name in skill_names:
        skill = get_skill(name)
        if skill:
            parts.append(f"# Skill: {skill['name']}\n\n{skill['body']}")
            for ref_name, ref_body in skill["references"].items():
                parts.append(f"\n## Reference: {ref_name}\n\n{ref_body}")
        else:
            parts.append(f"# Skill: {name}\n\n(Skill not found)")
    return "\n\n---\n\n".join(parts)