"""Turns a folder of your own photos into wallpapers the launcher can show on a small TV.

    python tools/wallpaper_prep.py ~/Pictures/trip /tmp/my-theme/wallpapers

Every JPEG, PNG, WebP and (with pillow-heif) HEIC file in the first folder is centre-cropped to 16:9, shrunk to
1280x720, darkened so the clock, the grid and the dock stay readable, and saved as 01.jpg, 02.jpg, ... in the
second folder. The originals are never touched: a target that is the source folder (by any spelling or
link), or an 01.jpg there that is a symlink or hard link to one of your photos, stops the run before
anything is written. Each picture is kept under --max-kb (300 by default, what
themes/README.md asks for) by lowering the JPEG quality a step at a time.

The darkening is painted into the picture, so wallpaper_dim can stay at 0 and the launcher draws no shade
layer. The numbers that worked on a Xiaomi Mi Box S (2 GB) are the defaults: brightness 0.25 and a gradient
that adds up to 60% black toward the bottom, where the dock sits.

Needs Pillow; HEIC (iPhone and many Android cameras) also needs pillow-heif:

    python -m pip install -r tools/requirements-photos.txt

Use pictures you have the right to show.
"""
import argparse
import os
import sys

EXTENSIONS = {".jpg", ".jpeg", ".png", ".webp", ".heic", ".heif"}


def parse_size(text):
    try:
        w, h = text.lower().split("x")
        w, h = int(w), int(h)
    except ValueError:
        raise argparse.ArgumentTypeError("size must look like 1280x720")
    if w < 16 or h < 9 or w > 7680 or h > 4320:
        raise argparse.ArgumentTypeError("size must be between 16x9 and 7680x4320")
    return w, h


def source_files(folder):
    """Picture files directly inside folder, in name order (so the numbering is stable)."""
    names = sorted(n for n in os.listdir(folder) if os.path.splitext(n)[1].lower() in EXTENSIONS)
    return [os.path.join(folder, n) for n in names if os.path.isfile(os.path.join(folder, n))]


def overlapping_outputs(files, target):
    """Names of the numbered outputs in target that already are, or link to, one of the source files.

    A symlink or hardlink called 01.jpg in the target would make the save overwrite an original, and
    one pointing at a later photo would do it before that photo's turn, so every planned name is
    checked against every source file up front, by (device, inode), before anything is written.
    """
    identities = {(info.st_dev, info.st_ino) for info in map(os.stat, files)}
    clashes = []
    for number in range(1, len(files) + 1):
        name = "%02d.jpg" % number
        try:
            info = os.stat(os.path.join(target, name))
        except OSError:
            continue
        if (info.st_dev, info.st_ino) in identities:
            clashes.append(name)
    return clashes


def darken(image, brightness, gradient):
    """Scale brightness, then blend toward black from top (0) to bottom (gradient)."""
    from PIL import Image, ImageEnhance
    image = ImageEnhance.Brightness(image).enhance(brightness)
    if gradient > 0:
        mask = Image.linear_gradient("L").resize(image.size).point(lambda v: int(v * gradient))
        image = Image.composite(Image.new("RGB", image.size, (0, 0, 0)), image, mask)
    return image


def prepare(path, out_path, size, brightness, gradient, quality, max_kb):
    """Writes one wallpaper and returns (size in KB, JPEG quality used)."""
    from PIL import Image, ImageOps
    with Image.open(path) as opened:
        image = ImageOps.exif_transpose(opened).convert("RGB")
    image = ImageOps.fit(image, size, Image.LANCZOS, centering=(0.5, 0.5))
    image = darken(image, brightness, gradient)
    q = quality
    while True:
        image.save(out_path, "JPEG", quality=q, optimize=True)
        kb = os.path.getsize(out_path) / 1024
        if kb <= max_kb or q <= 50:
            return round(kb), q
        q -= 6


def main(argv=None):
    parser = argparse.ArgumentParser(description="Resize and darken photos for the launcher's wallpaper folder.")
    parser.add_argument("source", help="folder with your photos")
    parser.add_argument("target", help="folder to write 01.jpg, 02.jpg, ... into (created if missing)")
    parser.add_argument("--size", type=parse_size, default=(1280, 720), help="default 1280x720")
    parser.add_argument("--brightness", type=float, default=0.25, help="0.1 to 1.0, default 0.25")
    parser.add_argument("--gradient", type=float, default=0.6, help="extra black toward the bottom, 0 to 0.9, default 0.6")
    parser.add_argument("--quality", type=int, default=84, help="starting JPEG quality, default 84")
    parser.add_argument("--max-kb", type=int, default=300, help="size limit per picture, default 300")
    args = parser.parse_args(argv)

    if not 0.1 <= args.brightness <= 1.0:
        parser.error("--brightness must be between 0.1 and 1.0")
    if not 0 <= args.gradient <= 0.9:
        parser.error("--gradient must be between 0 and 0.9")
    if not 30 <= args.quality <= 95:
        parser.error("--quality must be between 30 and 95")
    if not os.path.isdir(args.source):
        parser.error(f"{args.source} is not a folder")
    source_real = os.path.realpath(args.source)
    target_real = os.path.realpath(args.target)
    if target_real == source_real or target_real.startswith(source_real.rstrip(os.sep) + os.sep):
        parser.error("the target must be a different folder, and not inside the source: the originals are never overwritten")
    if os.path.exists(args.target) and os.path.samefile(args.source, args.target):
        parser.error("the target must be a different folder, and not inside the source: the originals are never overwritten")

    try:
        import PIL  # noqa: F401
    except ImportError:
        sys.exit("Pillow is missing: python -m pip install -r tools/requirements-photos.txt")
    try:
        import pillow_heif
        pillow_heif.register_heif_opener()
    except ImportError:
        pillow_heif = None

    files = source_files(args.source)
    if not files:
        sys.exit(f"no JPEG, PNG, WebP or HEIC pictures in {args.source}")
    clashes = overlapping_outputs(files, args.target)
    if clashes:
        sys.exit(f"{', '.join(clashes)} in {args.target} would overwrite your original photos "
                 "(a link or the same file); remove or rename them, or pick another target. Nothing was written.")
    os.makedirs(args.target, exist_ok=True)

    written = 0
    for number, path in enumerate(files, 1):
        name = os.path.basename(path)
        if os.path.splitext(name)[1].lower() in {".heic", ".heif"} and pillow_heif is None:
            print(f"skipped {name}: HEIC needs pillow-heif (python -m pip install -r tools/requirements-photos.txt)")
            continue
        out_path = os.path.join(args.target, "%02d.jpg" % number)
        try:
            kb, quality = prepare(path, out_path, args.size, args.brightness, args.gradient, args.quality, args.max_kb)
        except Exception as error:  # a corrupt picture must not stop the rest
            print(f"skipped {name}: {error}")
            continue
        written += 1
        note = "" if kb <= args.max_kb else f"  (over {args.max_kb} KB even at quality {quality})"
        print(f"{os.path.basename(out_path)}  <- {name}  {kb} KB, quality {quality}{note}")
    print(f"{written} of {len(files)} pictures written to {args.target}")
    return 0 if written else 1


if __name__ == "__main__":
    sys.exit(main())