"""Resize, quantize, and pack a photo into the panel's raw 4bpp format."""

from __future__ import annotations

import io

from PIL import Image, ImageEnhance, ImageOps

EPD_WIDTH = 800
EPD_HEIGHT = 480

# How each orientation maps the logically-composed image onto the native
# 800x480 panel. "portrait"/"portrait_flipped" compose at 480x800 (so the
# crop ratio matches how the frame actually hangs) and rotate into native
# space afterwards -- rotation happens after dithering, which is lossless
# (a pure pixel permutation). Which of 90/270 is "portrait" vs
# "portrait_flipped" is a convention pick; whichever way the frame is
# hung, one of the two is right.
ORIENTATION_TRANSPOSE = {
    "landscape": None,
    "landscape_flipped": Image.Transpose.ROTATE_180,
    "portrait": Image.Transpose.ROTATE_90,
    "portrait_flipped": Image.Transpose.ROTATE_270,
}


def logical_render_size(orientation: str) -> tuple[int, int]:
    """(width, height) the photo is composed/cropped at for this
    orientation, before rotating into native panel space."""
    if orientation in ("portrait", "portrait_flipped"):
        return EPD_HEIGHT, EPD_WIDTH
    return EPD_WIDTH, EPD_HEIGHT


def logical_to_native(x: float, y: float, orientation: str) -> tuple[int, int]:
    """Maps a point in logical (pre-rotation) frame space to native
    800x480 panel space, applying the same rotation ORIENTATION_TRANSPOSE
    applies to the pixels -- anything positioned in logical coordinates
    (e.g. face labels) needs this to stay attached to the rotated
    content. PIL's ROTATE_90 is counterclockwise; ROTATE_270 clockwise."""
    logical_w, logical_h = logical_render_size(orientation)
    if orientation == "landscape_flipped":
        return int(logical_w - 1 - x), int(logical_h - 1 - y)
    if orientation == "portrait":  # ROTATE_90 (CCW)
        return int(y), int(logical_w - 1 - x)
    if orientation == "portrait_flipped":  # ROTATE_270 (CW)
        return int(logical_h - 1 - y), int(x)
    return int(x), int(y)

# Approximate sRGB for each of the panel's 6 ink colors -- reasonable
# placeholders, not measured values (Waveshare doesn't publish exact
# color primaries for this panel). This is the fallback for any frame
# that hasn't tuned its own (Frame.palette_rgb, set from a frame's
# Configuration tab -- "Advanced configuration" -- once you can compare
# a rendered test image against the real panel; different panel units
# can vary enough to be worth calibrating per frame).
DEFAULT_PALETTE_RGB = [
    (0, 0, 0),  # BLACK
    (255, 255, 255),  # WHITE
    (255, 219, 0),  # YELLOW
    (207, 0, 15),  # RED
    (0, 39, 133),  # BLUE
    (0, 133, 55),  # GREEN
]

PALETTE_LABELS = ["Black", "White", "Yellow", "Red", "Blue", "Green"]

# The panel's actual 4-bit color codes (see firmware/components/epd7in3e),
# in the same order as DEFAULT_PALETTE_RGB/PALETTE_LABELS -- fixed by the
# hardware protocol, never user-configurable. 0x4 is intentionally unused
# upstream.
PANEL_CODES = [0x0, 0x1, 0x2, 0x3, 0x5, 0x6]


def palette_to_hex(palette_rgb: list) -> list[str]:
    """[(0,0,0), ...] -> ["#000000", ...], for pre-filling the Advanced
    configuration color pickers."""
    return ["#%02x%02x%02x" % tuple(c) for c in palette_rgb]


def hex_to_rgb(hex_str: str) -> tuple[int, int, int] | None:
    """"#1a2b3c" -> (26, 43, 60), or None for anything that isn't exactly
    a 6-hex-digit color (what <input type="color"> always sends, but a
    direct API call might not)."""
    hex_str = hex_str.strip().lstrip("#")
    if len(hex_str) != 6:
        return None
    try:
        return (int(hex_str[0:2], 16), int(hex_str[2:4], 16), int(hex_str[4:6], 16))
    except ValueError:
        return None


def _build_palette_image(palette_rgb: list) -> Image.Image:
    pal_img = Image.new("P", (1, 1))
    pal_img.putpalette([channel for rgb in palette_rgb for channel in rgb])
    return pal_img


def _plain_center_crop_box(
    img_width: int, img_height: int, target_width: int, target_height: int
) -> tuple[float, float, int, int]:
    """The largest target_width:target_height window centered in the
    source image -- the same box ImageOps.fit() computes internally when
    there's no face-aware shift to apply. Returns (left, top, crop_w,
    crop_h); left/top are floats (not yet rounded) since callers that go
    on to face-shift this box need the unrounded center point."""
    target_ratio = target_width / target_height
    if img_width / img_height > target_ratio:
        crop_h = img_height
        crop_w = int(crop_h * target_ratio)
    else:
        crop_w = img_width
        crop_h = int(crop_w / target_ratio)

    left = (img_width - crop_w) / 2
    top = (img_height - crop_h) / 2
    return left, top, crop_w, crop_h


def _has_bounding_box(face: dict) -> bool:
    """Immich has occasionally been observed to return a face entry with
    a still-pending or otherwise incomplete bounding box (a null field)
    -- treat it as undetected rather than crash on arithmetic with None."""
    return all(
        face.get(k) is not None
        for k in ("boundingBoxX1", "boundingBoxX2", "boundingBoxY1", "boundingBoxY2")
    )


def _face_aware_crop_box(
    img_width: int, img_height: int, target_width: int, target_height: int, faces: list[dict]
) -> tuple[int, int, int, int]:
    """Largest crop window matching target_width:target_height that fits
    inside the source image. Starts from the plain center crop and only
    shifts it the minimum amount needed to bring any faces that would
    otherwise be cut off back on screen -- an already-fine composition
    (faces already fully inside the center crop) is left untouched rather
    than re-centered on the faces. If the faces themselves span wider than
    the crop window allows, centers on their midpoint as best-effort,
    since there's no shift that fits them all regardless.

    Each face's box is given relative to its own imageWidth/imageHeight
    (the resolution Immich ran detection on), which may differ from the
    downloaded preview's resolution passed in here, so each box is scaled
    into img_width/img_height space before use.
    """
    min_x = min_y = float("inf")
    max_x = max_y = float("-inf")
    for face in faces:
        if not _has_bounding_box(face):
            continue
        face_w = face.get("imageWidth") or img_width
        face_h = face.get("imageHeight") or img_height
        scale_x = img_width / face_w
        scale_y = img_height / face_h
        min_x = min(min_x, face["boundingBoxX1"] * scale_x)
        max_x = max(max_x, face["boundingBoxX2"] * scale_x)
        min_y = min(min_y, face["boundingBoxY1"] * scale_y)
        max_y = max(max_y, face["boundingBoxY2"] * scale_y)

    left, top, crop_w, crop_h = _plain_center_crop_box(img_width, img_height, target_width, target_height)

    if max_x - min_x <= crop_w:
        if min_x < left:
            left = min_x
        elif max_x > left + crop_w:
            left = max_x - crop_w
    else:
        left = (min_x + max_x) / 2 - crop_w / 2

    if max_y - min_y <= crop_h:
        if min_y < top:
            top = min_y
        elif max_y > top + crop_h:
            top = max_y - crop_h
    else:
        top = (min_y + max_y) / 2 - crop_h / 2

    left = max(0, min(left, img_width - crop_w))
    top = max(0, min(top, img_height - crop_h))

    return (int(left), int(top), int(left) + crop_w, int(top) + crop_h)


# Display modes: how a photo's aspect ratio gets reconciled with the
# panel's. "crop_faces" falls back to "crop_fill" behavior when no faces
# were detected/passed. DEFAULT_DISPLAY_MODE matches this project's old
# always-on smart_crop_faces=True default.
DISPLAY_MODES = ["crop_fill", "crop_faces", "stretch_fill", "letterbox"]
DISPLAY_MODE_LABELS = {
    "crop_fill": "Crop to fill",
    "crop_faces": "Crop to faces",
    "stretch_fill": "Stretch to fill",
    "letterbox": "Shrink to fit",
}
DEFAULT_DISPLAY_MODE = "crop_faces"
LETTERBOX_BG = (255, 255, 255)


def _placement_transform(
    img_width: int, img_height: int, target_w: int, target_h: int,
    display_mode: str, faces: list[dict] | None = None,
) -> tuple[float, float, float, float]:
    """Returns (scale_x, scale_y, offset_x, offset_y) mapping a point in
    source-image pixel space to a point in target logical space, for the
    given display_mode. Shared by render_frame (which also does the
    actual pixel crop/resize/pad) and face_labels.py (label position
    math) -- they must stay in exact agreement or overlay labels drift
    off the people they're meant to point at."""
    if display_mode == "stretch_fill":
        return target_w / img_width, target_h / img_height, 0.0, 0.0
    if display_mode == "letterbox":
        scale = min(target_w / img_width, target_h / img_height)
        return scale, scale, (target_w - img_width * scale) / 2, (target_h - img_height * scale) / 2
    if display_mode == "crop_faces" and faces:
        left, top, right, bottom = _face_aware_crop_box(img_width, img_height, target_w, target_h, faces)
        crop_w, crop_h = right - left, bottom - top
    else:
        left, top, crop_w, crop_h = _plain_center_crop_box(img_width, img_height, target_w, target_h)
    scale_x, scale_y = target_w / crop_w, target_h / crop_h
    return scale_x, scale_y, -left * scale_x, -top * scale_y


def _compose(source: Image.Image, faces: list[dict] | None, orientation: str, display_mode: str) -> Image.Image:
    """Crop/resize/letterbox `source` per display_mode -- returns an RGB
    image at logical_render_size(orientation), before enhancement or
    quantization. See render_frame for what each display_mode does."""
    logical_w, logical_h = logical_render_size(orientation)
    fitted = ImageOps.exif_transpose(source.convert("RGB"))

    if display_mode == "stretch_fill":
        return fitted.resize((logical_w, logical_h), Image.LANCZOS)
    if display_mode == "letterbox":
        scale = min(logical_w / fitted.width, logical_h / fitted.height)
        new_w, new_h = max(1, round(fitted.width * scale)), max(1, round(fitted.height * scale))
        resized = fitted.resize((new_w, new_h), Image.LANCZOS)
        canvas = Image.new("RGB", (logical_w, logical_h), LETTERBOX_BG)
        canvas.paste(resized, ((logical_w - new_w) // 2, (logical_h - new_h) // 2))
        return canvas
    if display_mode == "crop_faces" and faces:
        box = _face_aware_crop_box(fitted.width, fitted.height, logical_w, logical_h, faces)
        return fitted.crop(box).resize((logical_w, logical_h), Image.LANCZOS)
    return ImageOps.fit(fitted, (logical_w, logical_h), method=Image.LANCZOS)  # crop_fill, or crop_faces w/ no faces


def _enhance(img: Image.Image, color_boost: float, contrast_boost: float) -> Image.Image:
    if color_boost != 1.0:
        img = ImageEnhance.Color(img).enhance(color_boost)
    if contrast_boost != 1.0:
        img = ImageEnhance.Contrast(img).enhance(contrast_boost)
    return img


def _quantize(img: Image.Image, palette_rgb: list | None, dither_strength: float) -> Image.Image:
    """RGB -> palette-quantized P-mode image, same size/orientation as
    `img` (no rotation here). dither_strength blends `img` toward its own
    flat (undithered) quantization before running Floyd-Steinberg on the
    blend: at 0 there's zero quantization error left to diffuse (so the
    result IS the flat quantization, no dithering texture at all); at 1
    it's `img` unchanged (full-strength dithering, this project's
    original always-on behavior); values between give a smooth continuum
    of dithering intensity rather than an on/off toggle."""
    palette_image = _build_palette_image(palette_rgb or DEFAULT_PALETTE_RGB)
    if dither_strength >= 1.0:
        return img.quantize(palette=palette_image, dither=Image.Dither.FLOYDSTEINBERG)
    if dither_strength <= 0.0:
        return img.quantize(palette=palette_image, dither=Image.Dither.NONE)
    flat = img.quantize(palette=palette_image, dither=Image.Dither.NONE).convert("RGB")
    blended = Image.blend(flat, img, dither_strength)
    return blended.quantize(palette=palette_image, dither=Image.Dither.FLOYDSTEINBERG)


def _transpose_and_pack(quantized: Image.Image, orientation: str) -> bytes:
    """Rotates a logical-space quantized image into native panel space
    and packs it 2 pixels/byte the way epd7in3e.c expects. Always
    returns exactly EPD_WIDTH*EPD_HEIGHT/2 bytes."""
    transpose = ORIENTATION_TRANSPOSE.get(orientation)
    if transpose is not None:
        quantized = quantized.transpose(transpose)
    pixels = quantized.load()

    out = bytearray(EPD_WIDTH * EPD_HEIGHT // 2)
    i = 0
    for y in range(EPD_HEIGHT):
        for x in range(0, EPD_WIDTH, 2):
            left = PANEL_CODES[pixels[x, y]]
            right = PANEL_CODES[pixels[x + 1, y]]
            out[i] = (left << 4) | right
            i += 1

    return bytes(out)


def render_frame(source: Image.Image, faces: list[dict] | None = None,
                 orientation: str = "landscape", palette_rgb: list | None = None,
                 display_mode: str = DEFAULT_DISPLAY_MODE, color_boost: float = 1.0,
                 contrast_boost: float = 1.0, dither_strength: float = 1.0) -> bytes:
    """Fits `source` to the panel's resolution, applies color/contrast
    enhancement, quantizes it to the 6-color palette, and packs 2
    pixels/byte the way epd7in3e.c expects. Always returns exactly
    EPD_WIDTH*EPD_HEIGHT/2 bytes.

    `display_mode` (see DISPLAY_MODES) picks how the photo's aspect ratio
    is reconciled with the panel's: crop_fill (center-crop to fill,
    excess trimmed), crop_faces (as crop_fill, but shifts the crop to
    keep `faces` on screen -- falls back to crop_fill if none), stretch_fill
    (fills exactly, aspect ratio not preserved), letterbox (whole photo
    visible, letterboxed with LETTERBOX_BG where it doesn't fill).

    `color_boost`/`contrast_boost` are PIL ImageEnhance factors (1.0 =
    unchanged, matching PIL's own convention); `dither_strength` is
    0.0-1.0 (see _quantize).

    `orientation` (see ORIENTATION_TRANSPOSE) composes the photo for how
    the frame physically hangs, then rotates into native panel space --
    the output byte layout is identical either way.

    `palette_rgb` overrides DEFAULT_PALETTE_RGB (a frame's tuned colors,
    see Frame.palette_rgb) -- None uses the default.
    """
    fitted = _enhance(_compose(source, faces, orientation, display_mode), color_boost, contrast_boost)
    quantized = _quantize(fitted, palette_rgb, dither_strength)
    return _transpose_and_pack(quantized, orientation)


def render_preview_png(source: Image.Image, faces: list[dict] | None = None,
                       orientation: str = "landscape", palette_rgb: list | None = None,
                       display_mode: str = DEFAULT_DISPLAY_MODE, color_boost: float = 1.0,
                       contrast_boost: float = 1.0, dither_strength: float = 1.0) -> bytes:
    """Identical composition/enhancement/quantization pipeline as
    render_frame, but returned as a normal browser-viewable PNG in
    logical (upright, as-the-frame-actually-hangs) orientation rather
    than packed native-panel bytes and rotation -- what the web UI's
    "how it will look on the frame" preview shows."""
    fitted = _enhance(_compose(source, faces, orientation, display_mode), color_boost, contrast_boost)
    quantized = _quantize(fitted, palette_rgb, dither_strength)
    buf = io.BytesIO()
    quantized.convert("RGB").save(buf, format="PNG")
    return buf.getvalue()


def render_placeholder(lines: list[str], qr_url: str | None = None,
                       orientation: str = "landscape", palette_rgb: list | None = None) -> bytes:
    """A readable full-panel message (plus an optional QR code) in the
    same packed format as render_frame -- what /frame/image serves for a
    frame that isn't claimed or configured yet, so a fresh device shows
    instructions instead of an error screen and never error-loops."""
    from PIL import ImageDraw, ImageFont

    logical_w, logical_h = logical_render_size(orientation)
    img = Image.new("RGB", (logical_w, logical_h), (255, 255, 255))
    draw = ImageDraw.Draw(img)

    title_font = ImageFont.load_default(size=34)
    body_font = ImageFont.load_default(size=24)

    qr_img = None
    if qr_url:
        import qrcode

        qr = qrcode.QRCode(border=1, box_size=1)
        qr.add_data(qr_url)
        qr.make(fit=True)
        raw = qr.make_image().get_image().convert("RGB")
        # Integer upscale with NEAREST keeps modules crisp on the panel.
        target = 220
        scale = max(1, target // raw.width)
        qr_img = raw.resize((raw.width * scale, raw.height * scale), Image.NEAREST)

    # Vertical layout: text block, then QR under it, centered as a group.
    line_heights = []
    for i, line in enumerate(lines):
        font = title_font if i == 0 else body_font
        bbox = draw.textbbox((0, 0), line, font=font)
        line_heights.append((line, font, bbox[2] - bbox[0], bbox[3] - bbox[1]))
    gap = 14
    text_h = sum(h for _, _, _, h in line_heights) + gap * (len(line_heights) - 1 if line_heights else 0)
    total_h = text_h + (qr_img.height + 28 if qr_img else 0)
    y = max(20, (logical_h - total_h) // 2)

    for line, font, w, h in line_heights:
        draw.text(((logical_w - w) // 2, y), line, fill=(0, 0, 0), font=font)
        y += h + gap

    if qr_img:
        img.paste(qr_img, ((logical_w - qr_img.width) // 2, y + 14))

    quantized = _quantize(img, palette_rgb, dither_strength=1.0)
    return _transpose_and_pack(quantized, orientation)