"""Remix: create one additional variant for an existing job, using the
cached original + rembg output and user-chosen filters/blends/opacity."""

from __future__ import annotations

from dataclasses import dataclass

from . import pipeline
from .pipeline import FilterAssets, JobPaths, PipelineError


@dataclass
class RemixChoice:
    bg_filter: str
    bg_blend: str
    fg_filter: str
    fg_blend: str
    opacity: str


def build_remix_options(assets: FilterAssets) -> dict[str, list[str]]:
    return {
        "background_filters": sorted(assets.background_names),
        "foreground_filters": sorted(assets.foreground_names),
        "blend_modes": sorted(assets.blend_modes),
    }


def create_remix_variant(job_id: str, choice: RemixChoice) -> dict:
    """Compose exactly one variant from explicit choices and append it to
    the job's meta. Raises PipelineError on failure (caller should show
    it to the user, no half-written manifest entries are ever created)."""
    stem = pipeline.sanitize_stem(job_id)
    paths: JobPaths = pipeline.job_paths(stem, ".jpg")
    if not paths.original.exists() or not paths.rembg.exists():
        raise PipelineError("Original oder Rembg-Bild fehlt fuer diesen Job — Remix nicht moeglich.")

    assets = pipeline.load_assets()
    if choice.bg_filter not in assets.commands:
        raise PipelineError(f"Unbekannter Background-Filter: {choice.bg_filter}")
    if choice.fg_filter not in assets.commands:
        raise PipelineError(f"Unbekannter Foreground-Filter: {choice.fg_filter}")
    if choice.bg_blend not in assets.blend_modes or choice.fg_blend not in assets.blend_modes:
        raise PipelineError("Unbekannter Blend-Modus.")

    manifest = pipeline.read_manifest(stem) or {
        "job_id": stem,
        "original_file": paths.original.name,
        "rembg_file": paths.rembg.name,
        "source_stem": stem,
        "created_at": pipeline.now_iso(),
        "variants": [],
    }
    variant_stem = pipeline.resolve_source_stem(manifest, paths)
    manifest.setdefault("source_stem", variant_stem)
    variant_id = pipeline.next_variant_id(manifest)

    entry = pipeline.compose_variant(
        paths,
        assets,
        variant_id=variant_id,
        source="remix",
        variant_stem=variant_stem,
        bg_name=choice.bg_filter,
        bg_mode=choice.bg_blend,
        fg_name=choice.fg_filter,
        fg_mode=choice.fg_blend,
        opacity=choice.opacity,
    )
    manifest["variants"].append(entry)
    pipeline.write_manifest(paths, manifest)
    return entry