"""Theme storage: flat JSON files under themes/."""

from __future__ import annotations

import json
import re
from dataclasses import dataclass
from pathlib import Path

THEMES_DIR = Path(__file__).resolve().parent.parent / "themes"

_SLUG_RE = re.compile(r"^[a-z0-9]+(?:-[a-z0-9]+)*$")


@dataclass
class Theme:
    slug: str
    name: str
    words: list[str]


class ThemeError(ValueError):
    """Raised for invalid theme input."""


def slugify(name: str) -> str:
    """Lowercase, replace non-alphanumeric runs with single hyphen, trim."""
    s = name.lower().strip()
    s = re.sub(r"[^a-z0-9]+", "-", s)
    s = s.strip("-")
    return s


def is_valid_slug(slug: str) -> bool:
    return bool(_SLUG_RE.match(slug))


def _path(slug: str) -> Path:
    if not is_valid_slug(slug):
        raise ThemeError(f"invalid slug: {slug!r}")
    return THEMES_DIR / f"{slug}.json"


def list_themes() -> list[Theme]:
    THEMES_DIR.mkdir(parents=True, exist_ok=True)
    out: list[Theme] = []
    for path in sorted(THEMES_DIR.glob("*.json")):
        slug = path.stem
        if not is_valid_slug(slug):
            continue
        try:
            data = json.loads(path.read_text(encoding="utf-8"))
            out.append(Theme(slug=slug, name=data.get("name", slug),
                             words=list(data.get("words", []))))
        except (json.JSONDecodeError, OSError):
            continue
    return out


def load_theme(slug: str) -> Theme:
    path = _path(slug)
    if not path.exists():
        raise ThemeError(f"theme not found: {slug!r}")
    data = json.loads(path.read_text(encoding="utf-8"))
    return Theme(slug=slug, name=data.get("name", slug),
                 words=list(data.get("words", [])))


def save_theme(slug: str, name: str, words: list[str]) -> Theme:
    if not is_valid_slug(slug):
        raise ThemeError(
            "slug must be lowercase letters, digits, and hyphens only"
        )
    name = name.strip()
    if not name:
        raise ThemeError("theme name is required")
    cleaned = [w.strip() for w in words if w.strip()]
    if not cleaned:
        raise ThemeError("theme must contain at least one word")
    THEMES_DIR.mkdir(parents=True, exist_ok=True)
    path = THEMES_DIR / f"{slug}.json"
    payload = {"name": name, "words": cleaned}
    path.write_text(json.dumps(payload, indent=2, ensure_ascii=False) + "\n",
                    encoding="utf-8")
    return Theme(slug=slug, name=name, words=cleaned)


def delete_theme(slug: str) -> None:
    path = _path(slug)
    if path.exists():
        path.unlink()


def parse_words_textarea(blob: str) -> list[str]:
    """One word per line; ignore blank lines and surrounding whitespace."""
    return [line.strip() for line in blob.splitlines() if line.strip()]