"""Download settings and file-type handling."""

from __future__ import annotations

from dataclasses import dataclass, field
from pathlib import Path

from sticker_downloader.errors import InvalidFileType

STATIC = "webp"
ANIMATED = "tgs"
VIDEO = "webm"
THUMBNAIL = "png"

#: Every type the downloader knows how to save, in a stable display order.
ALL_FILE_TYPES: tuple[str, ...] = (STATIC, ANIMATED, VIDEO, THUMBNAIL)

FILE_TYPE_HELP: dict[str, str] = {
    STATIC: "static stickers",
    ANIMATED: "animated stickers (Lottie)",
    VIDEO: "video stickers",
    THUMBNAIL: "PNG thumbnails",
}

DEFAULT_OUTPUT_DIR = Path("downloads")
DEFAULT_URL_FILE = Path("urls.txt")
DEFAULT_CONCURRENCY = 8
DEFAULT_RETRIES = 3
METADATA_FILE_NAME = "pack.json"
PACK_THUMBNAIL_STEM = "_pack_thumbnail"


@dataclass(frozen=True)
class DownloadConfig:
    """Everything that shapes a download run."""

    file_types: frozenset[str] = field(default_factory=lambda: frozenset(ALL_FILE_TYPES))
    output_dir: Path = DEFAULT_OUTPUT_DIR
    concurrency: int = DEFAULT_CONCURRENCY
    retries: int = DEFAULT_RETRIES
    overwrite: bool = False
    write_metadata: bool = True
    pack_thumbnail: bool = True
    emoji_names: bool = False
    dry_run: bool = False

    def __post_init__(self) -> None:
        unknown = sorted(self.file_types - set(ALL_FILE_TYPES))
        if unknown:
            raise InvalidFileType(f"unknown file type(s): {', '.join(unknown)}")
        if not self.file_types:
            raise InvalidFileType("at least one file type is required")
        if self.concurrency < 1:
            raise ValueError("concurrency must be at least 1")
        if self.retries < 1:
            raise ValueError("retries must be at least 1")

    @property
    def sorted_file_types(self) -> list[str]:
        """The requested types in canonical order, for stable output."""
        return [file_type for file_type in ALL_FILE_TYPES if file_type in self.file_types]

    def wants(self, file_type: str) -> bool:
        return file_type in self.file_types


def parse_file_types(raw: str | None) -> frozenset[str]:
    """Turn user input such as ``"webp, png"``, ``"all"`` or ``""`` into a type set.

    Empty input and ``"all"`` both mean "every supported type", matching what the
    interactive prompt advertises.
    """
    text = (raw or "").strip().lower()
    if not text or text == "all":
        return frozenset(ALL_FILE_TYPES)

    requested = [part.strip().lstrip(".") for part in text.replace(" ", ",").split(",")]
    selected = {part for part in requested if part}
    if not selected:
        raise InvalidFileType("no file types given")

    unknown = sorted(selected - set(ALL_FILE_TYPES))
    if unknown:
        raise InvalidFileType(
            f"unknown file type(s): {', '.join(unknown)}. "
            f"Supported: {', '.join(ALL_FILE_TYPES)}, or 'all'."
        )
    return frozenset(selected)