"""Pet generation orchestration — the base-draft → hatch flow.

1. :func:`generate_base_drafts` — a few cheap prompt-only "what should this pet
   look like" variants; the user picks one (or retries).
2. :func:`hatch_pet` — grounds one row strip per Hermes state on the chosen base,
   slices frames, composes + validates the atlas, and writes it to the store.

Splitting bounds cost (4 cheap base calls per round; the ~8 row calls happen
once, on the pet you keep) and gives each UI a natural preview/loading point.
"""

from __future__ import annotations

import logging
import time
from concurrent.futures import ThreadPoolExecutor, as_completed
from dataclasses import dataclass
from pathlib import Path
from typing import Callable, Iterator

from agent.pet.generate import atlas, imagegen, prompts
from agent.pet.generate.imagegen import GenerationError, SpriteProvider

logger = logging.getLogger(__name__)

# (event, detail) — e.g. ("row", "idle"), ("compose", ""), ("save", "<slug>").
ProgressFn = Callable[[str, str], None]

# Generations are independent network calls, fanned out so a hatch (~8 rows)
# doesn't blow the client's RPC timeout; capped to respect provider rate limits.
_MAX_PARALLEL_GENERATIONS = 4
# Row (re)generation attempts: early ones demand clean per-pose gutters, the
# last is lenient so a stubborn row still yields frames instead of dropping out.
_ROW_GEN_ATTEMPTS = 3
_MIN_FILLED_STATES = 6
_REQUIRED_STATES = frozenset({"idle", "running-right", "waving"})

# (substrings, friendly message), first match wins. Moderation is the big one:
# image models refuse trademarked characters / real people as an opaque 400.
_IMAGE_ERROR_HINTS: tuple[tuple[tuple[str, ...], str], ...] = (
    (
        ("moderation_blocked", "safety system", "content policy", "content_policy"),
        "The image provider blocked this prompt — its safety filter rejects "
        "trademarked characters and real people. Try an original description.",
    ),
    (
        ("api key", "unauthorized", "401", "auth"),
        "The image provider rejected the request — check your API key in Settings → Providers.",
    ),
    (("rate limit", "429"), "The image provider is rate-limiting — wait a moment and try again."),
)


@dataclass(frozen=True)
class HatchResult:
    """Outcome of a successful :func:`hatch_pet`."""

    slug: str
    display_name: str
    spritesheet: Path
    states: list[str]
    validation: dict


def _unlink_quietly(path: Path) -> None:
    try:
        path.unlink(missing_ok=True)
    except OSError:
        pass


def _harden_transparency(path: Path) -> Path:
    """Key out any solid backdrop the provider painted; save as an RGBA PNG.

    ``background=transparent`` is requested but honored inconsistently, so run the
    row extractor's chroma-key pass on every base draft. Best-effort: a decode
    failure leaves the original untouched.
    """
    from PIL import Image

    try:
        with Image.open(path) as opened:
            keyed = atlas.remove_background(opened.convert("RGBA"))
        keyed = atlas._clear_transparent_rgb(keyed)  # no colored halo on the dark UI
        # PNGs (any case) are hardened in place: with_suffix(".png") on ".PNG" would
        # name the same file on case-insensitive filesystems and the unlink below
        # would delete the hardened output.
        out = path if path.suffix.lower() == ".png" else path.with_suffix(".png")
        keyed.save(out, format="PNG")
        if out != path:
            # Nothing prunes cache/images outside the gateway loop: drop the
            # non-PNG original the hardened PNG replaces.
            _unlink_quietly(path)
        return out
    except Exception as exc:  # noqa: BLE001 - cosmetic; fall back to the raw image
        logger.debug("base draft transparency hardening failed for %s: %s", path, exc)
        return path


def _run_parallel(fn, items, *, cancelled, on_cancel_log: str) -> Iterator:
    """Fan *fn* over *items* in a pool, yielding results in completion order.

    ``as_completed`` runs on the caller's (request) thread, so callbacks fired
    from the results inherit the request's bound transport, unlike the workers.
    Once *cancelled* trips, queued work is cancelled and in-flight results dropped.
    """
    workers = max(1, min(len(items), _MAX_PARALLEL_GENERATIONS))
    with ThreadPoolExecutor(max_workers=workers) as pool:
        futures = [pool.submit(fn, item) for item in items]
        for fut in as_completed(futures):
            if cancelled():
                logger.info(on_cancel_log)
                for pending in futures:
                    pending.cancel()
                break
            yield fut.result()


def generate_base_drafts(
    concept: str,
    *,
    n: int = 4,
    style: str = "auto",
    reference_images: list[Path] | None = None,
    provider: SpriteProvider | None = None,
    on_draft: Callable[[int, Path], None] | None = None,
    is_cancelled: Callable[[], bool] | None = None,
) -> list[Path]:
    """Generate *n* candidate base looks for *concept*; returns image paths.

    Drafts run concurrently and are hardened to transparent cutouts;
    *on_draft(index, path)* fires as each finishes so UIs can stream previews.
    *is_cancelled* is polled cooperatively (unstarted drafts skipped, queued work
    cancelled, in-flight results dropped).
    """
    # A user reference image grounds every draft, so it needs a reference-capable provider.
    refs = reference_images or None
    sprite = provider or imagegen.resolve_provider(require_references=bool(refs))
    cancelled = is_cancelled or (lambda: False)

    logger.info("pet generate: drafting %d base looks for %r (style=%s)", n, concept, style)

    def _one(index: int) -> tuple[int, Path | None, str | None]:
        if cancelled():
            return index, None, None
        t0 = time.monotonic()
        # Distinct variation nudge per draft so the options aren't near-duplicates.
        variation = prompts.BASE_VARIATIONS[index % len(prompts.BASE_VARIATIONS)]
        prompt = prompts.build_base_prompt(concept, style=style, variation=variation)
        try:
            out = imagegen.generate(prompt, n=1, reference_images=refs, provider=sprite, prefix="pet_base")
        except Exception as exc:  # noqa: BLE001 - tolerate a single failed draft
            logger.warning("pet generate: draft %d failed after %.1fs: %s", index, time.monotonic() - t0, exc)
            return index, None, str(exc)
        if not out:
            logger.warning("pet generate: draft %d produced no image", index)
            return index, None, "the image provider returned no image"
        logger.info("pet generate: draft %d ready in %.1fs", index, time.monotonic() - t0)
        return index, _harden_transparency(out[0]), None

    results: dict[int, Path] = {}
    errors: list[str] = []
    for index, path, err in _run_parallel(
        _one, range(n), cancelled=cancelled, on_cancel_log="pet generate: cancelled — dropping remaining drafts"
    ):
        if path is None:
            if err:
                errors.append(err)
            continue
        results[index] = path
        if on_draft is not None:
            try:
                on_draft(index, path)
            except Exception as exc:  # noqa: BLE001 - progress is best-effort
                logger.debug("on_draft callback failed: %s", exc)

    drafts = [results[i] for i in sorted(results)]
    if not drafts and not cancelled():
        # Surface *why*: the most common failure reason is the representative cause.
        if not errors:
            raise GenerationError("image generation produced no usable drafts")
        from collections import Counter

        raise GenerationError(_humanize_image_error(Counter(errors).most_common(1)[0][0]))
    return drafts


def _humanize_image_error(error: str) -> str:
    """Turn a raw provider error into a friendly, actionable sentence."""
    low = error.lower()
    for needles, message in _IMAGE_ERROR_HINTS:
        if any(s in low for s in needles):
            return message
    return error.splitlines()[0].strip()[:200]  # first line, sans provider envelope


def hatch_pet(
    *,
    base_image: str | Path,
    slug: str,
    display_name: str = "",
    description: str = "",
    concept: str = "",
    style: str = "auto",
    on_progress: ProgressFn | None = None,
    provider: SpriteProvider | None = None,
    is_cancelled: Callable[[], bool] | None = None,
) -> HatchResult:
    """Turn an approved base image into a full, installed Hermes pet.

    Idle falls back to the base look so the pet always renders. Raises
    :class:`GenerationError` on failure. *is_cancelled* is polled cooperatively
    and, once tripped, aborts before composing/saving so a stopped hatch never
    writes a half-built pet.
    """
    base = Path(base_image)
    if not base.is_file():
        raise GenerationError(f"base image not found: {base}")

    sprite = provider or imagegen.resolve_provider(require_references=True)
    progress = on_progress or (lambda *_: None)
    cancelled = is_cancelled or (lambda: False)
    label = concept or display_name or slug

    frames_by_state: dict[str, list] = {}
    total_rows = len(atlas.ROW_SPECS)
    logger.info("pet hatch %r: generating %d animation rows", slug, total_rows)

    def _gen_row(spec: tuple[str, int, int]) -> tuple[str, list | None]:
        state, _row, count = spec
        if cancelled():
            return state, None
        t0 = time.monotonic()
        last_exc: Exception | None = None
        # Self-healing: a roll whose poses touch (no gutters) slices badly, so
        # ``components`` (raises on touching poses) drives regeneration and only
        # the final attempt uses lenient ``auto`` slicing.
        for attempt in range(_ROW_GEN_ATTEMPTS):
            if cancelled():
                return state, None
            strict = attempt < _ROW_GEN_ATTEMPTS - 1
            strips: list[Path] = []
            try:
                strips = imagegen.generate(
                    prompts.build_row_prompt(state, count, label, style=style),
                    n=1,
                    reference_images=[base],
                    provider=sprite,
                    prefix=f"pet_row_{state}",
                    # Wider canvas: each frame gets real horizontal room and clean gutters.
                    aspect_ratio="landscape",
                )
                # fit=False keeps raw columns so normalize_cells registers the whole pet at once.
                method = "components" if strict else "auto"
                frames = atlas.extract_strip_frames(strips[0], count, method=method, fit=False)
                logger.info(
                    "pet hatch %r: row %r ready in %.1fs (attempt %d)",
                    slug, state, time.monotonic() - t0, attempt + 1,
                )
                return state, frames
            except Exception as exc:  # noqa: BLE001 - retried; one bad row is tolerated
                last_exc = exc
                logger.warning(
                    "pet hatch %r: row %r attempt %d/%d failed: %s",
                    slug, state, attempt + 1, _ROW_GEN_ATTEMPTS, exc,
                )
            finally:
                # Strips are intermediates already decoded into memory; nothing
                # prunes cache/images outside the gateway loop, so drop them now.
                for strip in strips:
                    _unlink_quietly(Path(strip))
        logger.warning(
            "pet hatch %r: row %r gave up after %.1fs: %s",
            slug, state, time.monotonic() - t0, last_exc,
        )
        return state, None

    # running-left is mirrored from running-right (consistent, one fewer generation).
    generated_specs = [spec for spec in atlas.ROW_SPECS if spec[0] != "running-left"]
    done = 0
    for state, frames in _run_parallel(
        _gen_row,
        generated_specs,
        cancelled=cancelled,
        on_cancel_log=f"pet hatch {slug!r}: cancelled — dropping remaining rows",
    ):
        done += 1
        progress("row", f"{state}:{done}:{total_rows}")
        if frames:
            frames_by_state[state] = frames

    if cancelled():
        raise GenerationError("hatch cancelled")

    # Per-frame mirror preserves order/timing. A missing running-right is
    # rejected below: a pet without its canonical walk cycle is a failed hatch.
    right = frames_by_state.get("running-right")
    if right:
        done += 1
        progress("row", f"running-left:{done}:{total_rows}")
        frames_by_state["running-left"] = atlas.mirror_frames(right)
        logger.info("pet hatch %r: row 'running-left' mirrored from running-right", slug)
    else:
        logger.warning("pet hatch %r: no running-right to mirror; left walk left empty", slug)

    if not frames_by_state.get("idle"):  # the renderer's resting fallback — guarantee it
        progress("row", "idle-fallback")
        frames_by_state["idle"] = [atlas.single_frame(base, fit=False)]

    progress("compose", "")
    logger.info("pet hatch %r: composing atlas from %d states", slug, len(frames_by_state))
    # One shared scale + baseline across states so the pet never slides or pulses.
    sheet = atlas.compose_atlas(atlas.normalize_cells(frames_by_state))
    validation = atlas.validate_atlas(sheet)
    if not validation["ok"]:
        raise GenerationError("; ".join(validation["errors"]) or "atlas validation failed")
    filled_states = set(validation["filled_states"])
    missing_required = sorted(_REQUIRED_STATES - filled_states)
    if missing_required:
        raise GenerationError(f"missing required animation row(s): {', '.join(missing_required)}")
    if len(filled_states) < _MIN_FILLED_STATES:
        raise GenerationError(
            f"only {len(filled_states)}/{len(atlas.ROW_SPECS)} animation rows were usable; regenerate"
        )

    from agent.pet import store

    progress("save", slug)
    logger.info("pet hatch %r: saving pet", slug)
    pet = store.register_local_pet(
        sheet,
        slug=slug,
        display_name=display_name or slug,
        description=description,
    )
    return HatchResult(
        slug=pet.slug,
        display_name=pet.display_name,
        spritesheet=pet.spritesheet,
        states=validation["filled_states"],
        validation=validation,
    )