from __future__ import annotations

import configparser
import re
from dataclasses import dataclass
from pathlib import Path

import tomlkit

from .paths import user_config_dir

try:  # pragma: no cover - fallback when setuptools is missing
    from setuptools import PackageFinder  # type: ignore
except Exception:  # pragma: no cover - defensive
    PackageFinder = None  # type: ignore[assignment]

# ---------------------------------------------------------------------------
# Dev links registry
# ---------------------------------------------------------------------------


class DevLinkError(Exception):
    """Raised when development link operations fail."""


@dataclass
class DevLink:
    provider_id: str
    defaults_path: Path
    link_path: Path


_PEP503_RE = re.compile(r"[-_.]+")
_VALID_RE = re.compile(r"^[a-z0-9-]+$")


def normalize_provider_id(name: str) -> str:
    """PEP 503 normalize ``name``.

    ``name`` is normalised to lowercase with hyphens and must not contain path
    separators or ``..`` segments.
    """

    stripped = name.strip().lower()
    norm = _PEP503_RE.sub("-", stripped)
    if (
        "/" in stripped
        or "\\" in stripped
        or ".." in stripped
        or not _VALID_RE.fullmatch(norm)
    ):
        raise ValueError(f"invalid provider id: {name!r}")
    return norm


def _dev_dir() -> Path:
    return Path(user_config_dir("sigil")) / "dev"


def link(provider: str, defaults_path: Path, *, validate: bool = True) -> DevLink:
    pid = normalize_provider_id(provider)
    defaults_path = Path(defaults_path).expanduser().resolve()
    if not defaults_path.is_file():
        raise DevLinkError(f"Defaults file not found: {defaults_path}")
    if defaults_path.name != "settings.ini" or defaults_path.parent.name != ".sigil":
        raise DevLinkError("Defaults file must be inside a '.sigil' directory")
    if validate:
        validate_defaults_file(defaults_path, pid)
    dir_ = _dev_dir()
    dir_.mkdir(parents=True, exist_ok=True)
    link_path = dir_ / f"{pid}.ini"
    cfg = configparser.ConfigParser()
    cfg["link"] = {"defaults": str(defaults_path)}
    with link_path.open("w") as f:
        cfg.write(f)
    return DevLink(pid, defaults_path, link_path)


def unlink(provider: str) -> bool:
    pid = normalize_provider_id(provider)
    link_path = _dev_dir() / f"{pid}.ini"
    if link_path.exists():
        link_path.unlink()
        return True
    return False


def get(provider: str) -> DevLink | None:
    pid = normalize_provider_id(provider)
    link_path = _dev_dir() / f"{pid}.ini"
    if not link_path.is_file():
        return None
    cfg = configparser.ConfigParser()
    try:
        cfg.read(link_path)
    except Exception:
        return None
    defaults = cfg.get("link", "defaults", fallback=None)
    if not defaults:
        return None
    return DevLink(pid, Path(defaults), link_path)


def list_links(must_exist_on_disk: bool = False) -> dict[str, Path]:
    dir_ = _dev_dir()
    if not dir_.is_dir():
        return {}
    result: dict[str, Path] = {}
    for file in dir_.glob("*.ini"):
        dl = get(file.stem)
        if dl is None:
            continue
        if must_exist_on_disk and not dl.defaults_path.exists():
            continue
        result[dl.provider_id] = dl.defaults_path
    return result


# ---------------------------------------------------------------------------
# Defaults validation
# ---------------------------------------------------------------------------


class DefaultsValidationError(Exception):
    """Raised when a defaults file is invalid."""


_KEY_RE = re.compile(r"^[a-z0-9][a-z0-9_]*(\.[a-z0-9_]+)*$")


def validate_defaults_file(path: Path, provider_id: str) -> None:
    """Validate ``path`` for ``provider_id``.

    The file must contain a ``[<provider_id>]`` section and all keys in that
    section must be dotted names using lowercase letters, digits, and optional
    underscores. Keys must start with a letter or digit.
    """

    path = Path(path).expanduser().resolve()
    if not path.is_file():
        raise DefaultsValidationError("defaults file not found")

    parser = configparser.ConfigParser()
    try:
        parser.read(path)
    except Exception as exc:  # pragma: no cover - defensive
        raise DefaultsValidationError(str(exc)) from exc

    section = provider_id
    if section not in parser:
        raise DefaultsValidationError("missing provider section")
    for key in parser[section]:
        if not _KEY_RE.match(key):
            raise DefaultsValidationError(f"invalid key: {key}")


# ---------------------------------------------------------------------------
# pyproject.toml helpers
# ---------------------------------------------------------------------------


def import_package_from(ini_path: Path) -> str:
    """Infer the import package name from ``ini_path``."""

    ini_path = Path(ini_path).resolve()
    if PackageFinder is not None:
        for ancestor in ini_path.parents:
            for base in [ancestor / "src", ancestor]:
                if not base.is_dir():
                    continue
                for pkg in PackageFinder.find(where=[str(base)]):
                    pkg_dir = base / Path(pkg.replace(".", "/"))
                    if pkg_dir / ".sigil" / "settings.ini" == ini_path:
                        return pkg
    return ini_path.parent.parent.name


def ensure_sigil_package_data(project_root: Path, package: str) -> None:
    """Ensure ``pyproject.toml`` includes ``.sigil`` package data for *package*.

    If ``pyproject.toml`` is missing or can't be parsed, this is a no-op.
    The function sets ``[tool.setuptools.package-data][<package>]`` to
    ``[".sigil/*"]``. Other packages' configuration is preserved.
    """

    ppt = project_root / "pyproject.toml"
    if not ppt.is_file():
        print("Error locating pyproject.toml")
        return

    try:  # pragma: no cover - defensive
        doc = tomlkit.parse(ppt.read_text(encoding="utf-8"))
    except Exception:  # pragma: no cover - defensive
        print("Error reading pyproject.toml")
        return

    tool = doc.setdefault("tool", tomlkit.table())
    st = tool.setdefault("setuptools", tomlkit.table())
    pd = st.setdefault("package-data", tomlkit.table())

    changed = False
    arr = pd.get(package)

    if not isinstance(arr, tomlkit.items.Array):
        new_arr = tomlkit.array()
        new_arr.multiline(False)
        if arr is not None:
            new_arr.append(getattr(arr, "value", arr))
        pd[package] = new_arr
        arr = new_arr
        changed = True

    existing = set()
    for item in arr:
        existing.add(getattr(item, "value", item))
    if ".sigil/*" not in existing:
        arr.append(".sigil/*")
        changed = True

    if changed:
        ppt.write_text(tomlkit.dumps(doc), encoding="utf-8")
