import logging
import os
import sys
from datetime import datetime
from pathlib import Path
from typing import List

logger = logging.getLogger(__name__)

SUPPORTED_IMAGE_EXTENSIONS = {".png", ".jpg", ".jpeg", ".webp"}


def is_supported_image(path):
    """Return True if path has a supported image extension (case-insensitive)."""
    return Path(path).suffix.lower() in SUPPORTED_IMAGE_EXTENSIONS


# ---------------------------------------------------------------------------
# Path helpers
# ---------------------------------------------------------------------------

def get_app_dir():
    """Return the program root directory (read-only program files) as a Path.

    PyInstaller onedir: directory that contains the .exe. In the launcher
    layout (docs/10-lan-update.md) this is the app\\ folder, replaced wholesale
    on update.
    Development: project root (three levels above this file:
        src/services/file_service.py -> src/services -> src -> project root).

    Resources live here; writable user data does not — use get_data_dir().
    """
    if getattr(sys, "frozen", False):
        return Path(sys.executable).resolve().parent
    return Path(__file__).resolve().parent.parent.parent


def get_data_dir():
    """Return the writable data root (config, templates, logs, output) as a Path.

    Kept separate from the program root so that replacing the program on update
    never touches user data (docs/10-lan-update.md §5). Resolution order:

    1. CMBOT_DATA_DIR environment variable, when set — explicit override for
       tests or special deployments.
    2. Packaged (sys.frozen) → ~/.cmbot (%USERPROFILE%\\.cmbot): always writable,
       per-user, independent of where the program is installed, so it works even
       when launched directly rather than through Launcher.exe.
    3. Development → project root, so dev runs don't pollute the home directory.
    """
    env = os.environ.get("CMBOT_DATA_DIR", "").strip()
    if env:
        return Path(env)
    if getattr(sys, "frozen", False):
        return Path.home() / ".cmbot"
    return get_app_dir()


def get_resource_path(relative_path):
    """Return absolute Path for a resource file under the program root.

    Development resources live under src/resources/. In a PyInstaller onedir
    build, resources are copied next to the executable under resources/.
    """
    if getattr(sys, "frozen", False):
        return get_app_dir() / "resources" / relative_path
    return get_app_dir() / "src" / "resources" / relative_path


def get_config_path(relative_path):
    """Return absolute Path for a file under <data_dir>/config/."""
    return get_data_dir() / "config" / relative_path


def get_log_dir():
    """Return <data_dir>/logs/ as a Path, creating the directory if absent."""
    d = get_data_dir() / "logs"
    d.mkdir(parents=True, exist_ok=True)
    return d


def _is_dir_writable(path):
    """Create *path* and probe it; True if a file can be written there."""
    try:
        path.mkdir(parents=True, exist_ok=True)
        probe = path / ".write_test"
        probe.write_text("x", encoding="ascii")
        probe.unlink()
        return True
    except OSError:
        return False


# Default export folder names, placed next to Launcher.exe in the packaged layout.
_OUTPUT_DIR_NAME = "合并后的图片"
_OUTFIT_OUTPUT_DIR_NAME = "穿搭图片"


def get_output_dir():
    """Return the default export directory as a Path, creating it if absent.

    Packaged: <install root>\\合并后的图片 (next to Launcher.exe — easy to find
    and NOT replaced on update, unlike app\\). Install root is the parent of the
    app\\ folder (get_app_dir()). Falls back to <data_dir>/output if the install
    root is not writable. Development: <data_dir>/output (the project dir).

    This is only the default; the user's chosen output_dir takes precedence.
    """
    if getattr(sys, "frozen", False):
        candidate = get_app_dir().parent / _OUTPUT_DIR_NAME
        if _is_dir_writable(candidate):
            return candidate
    d = get_data_dir() / "output"
    d.mkdir(parents=True, exist_ok=True)
    return d


def get_outfit_output_dir():
    """Return the default AI outfit output directory as a Path.

    Packaged: <install root>\\穿搭图片 (next to Launcher.exe, not inside app\\).
    Falls back to <data_dir>/output/穿搭图片 if the preferred location is not
    writable. Development: <project root>/穿搭图片.

    User-selected outfit_output_dir still takes precedence in the UI.
    """
    if getattr(sys, "frozen", False):
        candidate = get_app_dir().parent / _OUTFIT_OUTPUT_DIR_NAME
    else:
        candidate = get_app_dir() / _OUTFIT_OUTPUT_DIR_NAME

    if _is_dir_writable(candidate):
        return candidate

    d = get_data_dir() / "output" / _OUTFIT_OUTPUT_DIR_NAME
    d.mkdir(parents=True, exist_ok=True)
    return d


# ---------------------------------------------------------------------------
# 文件夹扫描
# ---------------------------------------------------------------------------

def scan_image_folder(folder) -> List:
    """Recursively scan *folder* for supported images.

    Returns a list of ImageAsset objects (selected=True by default).
    Skips unsupported files and logs them at DEBUG level.
    Raises OSError if *folder* does not exist or is not a directory.
    """
    from core.models import ImageAsset

    folder = Path(folder)
    if not folder.exists():
        raise OSError("Folder not found: {}".format(folder))
    if not folder.is_dir():
        raise OSError("Path is not a directory: {}".format(folder))

    assets = []
    skipped_count = 0

    for entry in sorted(folder.rglob("*")):
        if not entry.is_file():
            continue
        if is_supported_image(entry):
            assets.append(ImageAsset(path=entry))
        else:
            skipped_count += 1
            logger.debug("Skipped unsupported file: %s", entry)

    if skipped_count:
        logger.info(
            "Skipped %d unsupported file(s) in %s", skipped_count, folder
        )
    logger.info("Found %d image(s) in %s", len(assets), folder)
    return assets


# ---------------------------------------------------------------------------
# 安全输出文件名
# ---------------------------------------------------------------------------

def timestamped_run_dir(base_dir):
    """Return base_dir/<YYYYmmdd_HHMMSS> for grouping one export run.

    Compute this once per export run (a batch, or a single export) and pass the
    result as the output_dir to make_safe_output_path, so repeated runs land in
    separate timestamped folders instead of mixing together.
    """
    return Path(base_dir) / datetime.now().strftime("%Y%m%d_%H%M%S")


def make_safe_output_path(output_dir, garment_path, print_path, output_format="PNG"):
    """Return an output Path that will not overwrite an existing file.

    Outputs are grouped by print into a subfolder named after the print file:
        <output_dir>/<print_stem>/<garment_stem>_<print_stem>.<ext>
    If that path exists, appends _1, _2, ... until a free slot is found.
    (The composer creates the subfolder when saving.)
    """
    ext = ".png" if output_format.upper() == "PNG" else ".jpg"
    target_dir = Path(output_dir) / Path(print_path).stem
    stem = "{}_{}".format(Path(garment_path).stem, Path(print_path).stem)

    candidate = target_dir / (stem + ext)
    counter = 1
    while candidate.exists():
        candidate = target_dir / ("{}_{}{}".format(stem, counter, ext))
        counter += 1

    return candidate