"""Encode images as base64 data URIs for llama.cpp vision chat handlers.

Shared by the Mac collector (attachments) and the UI (manual upload).
"""
from __future__ import annotations

import base64
import mimetypes
from pathlib import Path

# Skip anything bigger than this to keep payloads/context sane.
MAX_BYTES = 4 * 1024 * 1024  # 4 MB

IMAGE_MIMES = {"image/png", "image/jpeg", "image/gif", "image/webp", "image/heic"}


def is_image(path: str) -> bool:
    mime, _ = mimetypes.guess_type(path)
    return mime in IMAGE_MIMES


def _heic_to_jpeg(p: Path) -> bytes | None:
    """Transcode HEIC/HEIF to JPEG bytes (pillow-heif), or None if unavailable.
    llama.cpp's clip handler can't decode HEIC, so raw pass-through would fail
    or waste context — and iPhone attachments are predominantly HEIC."""
    try:
        import io

        import pillow_heif
        from PIL import Image

        pillow_heif.register_heif_opener()
        img = Image.open(p).convert("RGB")
        buf = io.BytesIO()
        img.save(buf, format="JPEG", quality=88)
        return buf.getvalue()
    except Exception:  # noqa: BLE001  no pillow-heif / corrupt file -> skip
        return None


def to_data_uri(path: str) -> str | None:
    """Return a `data:<mime>;base64,...` URI, or None if not a usable image.
    HEIC is transcoded to JPEG (the vision stack can't decode HEIC); when
    transcoding isn't available the file is skipped, never sent undecodable."""
    p = Path(path)
    if not p.exists() or p.stat().st_size > MAX_BYTES:
        return None
    mime, _ = mimetypes.guess_type(str(p))
    if mime not in IMAGE_MIMES:
        return None
    if mime == "image/heic" or p.suffix.lower() in (".heic", ".heif"):
        jpeg = _heic_to_jpeg(p)
        if jpeg is None:
            return None
        return "data:image/jpeg;base64," + base64.b64encode(jpeg).decode("ascii")
    b64 = base64.b64encode(p.read_bytes()).decode("ascii")
    return f"data:{mime};base64,{b64}"


def paths_to_data_uris(paths: list[str]) -> list[str]:
    return [u for u in (to_data_uri(p) for p in paths or []) if u]