"""Preceding / overlap logic — extracted from the original process_iteration().

Implements P1 mode (iter 0: first frame is the single preceding frame) and
P9 mode (iter > 0: last N generated frames are the preceding frames), and
renders matching preceding scene/fg projections.

We deliberately mirror the original semantics so overlap-aware iterative
inference behaves identically.
"""
from __future__ import annotations

from typing import List, Optional, Tuple

import numpy as np
import torch

from .projection import blend_fg_over_scene, render_scene_proj_latent
from .fg import encode_first_frame_fg_to_latent
from .precomputed import encode_proj_frames_to_latent, subset_video_frames


def build_preceding_p1(state,
                       options,
                       output_size: Tuple[int, int],
                       t0: int,
                       pipeline,
                       use_fg_proj: bool) -> Tuple[Optional[np.ndarray],
                                                   Optional[torch.Tensor],
                                                   Optional[torch.Tensor]]:
    """P1 preceding: first frame + scene_proj at first frame pose + (optional) fg.

    Returns
    -------
    preceding_frames     : (1, H, W, 3) uint8 or None
    preceding_scene_proj : [16, 1, h, w] or None
    preceding_fg_proj    : [16, 1, h, w] or None
    """
    max_preceding = max(0, int(options.max_preceding_frames_first_iter))
    if max_preceding < 1:
        return None, None, None

    first_frame_np = np.array(state.current_first_frame)
    preceding_frames = first_frame_np[np.newaxis, ...]

    use_mp4_scene = bool(state.__dict__.get("use_mp4_scene", False))
    use_mp4_fg = bool(state.__dict__.get("use_mp4_fg", use_mp4_scene))
    blend_fg_into_scene = bool(state.__dict__.get("blend_fg_into_scene", False))
    scene_frames = state.__dict__.get("scene_proj_frames")
    fg_frames = state.__dict__.get("fg_proj_frames")

    preceding_scene_proj = None
    preceding_fg_proj = None

    fg_blend_frames = None
    if blend_fg_into_scene and fg_frames is not None:
        fg_blend_frames = subset_video_frames(fg_frames, [t0], output_size)

    if use_mp4_scene and scene_frames is not None:
        # scene_proj at the first-frame pose <- bg_projection.mp4 frame t0.
        if fg_blend_frames is not None:
            scene_sub = subset_video_frames(scene_frames, [t0], output_size)
            blended = blend_fg_over_scene(scene_sub, fg_blend_frames)
            preceding_scene_proj = encode_proj_frames_to_latent(
                frames_all=blended,
                frame_indices=list(range(len(blended))),
                output_size=output_size,
                vae=pipeline.vae, device=pipeline.device, dtype=pipeline.dtype,
            )
        else:
            preceding_scene_proj = encode_proj_frames_to_latent(
                frames_all=scene_frames,
                frame_indices=[t0],
                output_size=output_size,
                vae=pipeline.vae, device=pipeline.device, dtype=pipeline.dtype,
            )

    if not use_mp4_scene and state.points_world is not None:
        preceding_scene_proj = render_scene_proj_latent(
            points_world=state.points_world,
            colors=state.colors,
            colored_mask=state.colored_mask,
            target_frame_indices=[t0],
            poses_c2w=state.poses_c2w,
            intrinsics=state.intrinsics,
            intrinsics_size=state.intrinsics_size,
            output_size=output_size,
            vae=pipeline.vae,
            device=pipeline.device,
            dtype=pipeline.dtype,
            renderer=state.__dict__.get("scene_proj_renderer", "splat2d"),
            splat_rect_size=state.__dict__.get("scene_proj_splat_rect_size", 10),
            fg_blend_frames=fg_blend_frames,
        )

    if use_fg_proj and use_mp4_fg and fg_frames is not None:
        # fg_proj at the first-frame pose <- fg_projection.mp4 frame t0
        # (the dynamic-only render at camera 0, == first-frame fg).
        preceding_fg_proj = encode_proj_frames_to_latent(
            frames_all=fg_frames,
            frame_indices=[t0],
            output_size=output_size,
            vae=pipeline.vae, device=pipeline.device, dtype=pipeline.dtype,
        )
    elif use_fg_proj and state.initial_fg_only_mask is not None:
        preceding_fg_proj = encode_first_frame_fg_to_latent(
            first_frame_rgb=first_frame_np,
            fg_mask=state.initial_fg_only_mask,
            output_size=output_size,
            vae=pipeline.vae,
            device=pipeline.device,
            dtype=pipeline.dtype,
        )

    return preceding_frames, preceding_scene_proj, preceding_fg_proj


def build_preceding_p9(state,
                       options,
                       output_size: Tuple[int, int],
                       target_frame_indices: List[int],
                       pipeline) -> Tuple[Optional[np.ndarray],
                                          Optional[torch.Tensor],
                                          Optional[torch.Tensor]]:
    """P9 preceding: last N generated frames + scene_proj at their poses.

    fg_proj follows the configured source independently from scene_proj, so
    hybrid scene-from-pointcloud / fg-from-mp4 conditioning can keep P9 fg.
    """
    max_preceding = max(0, int(options.max_preceding_frames_other_iter))
    if max_preceding < 1 or len(state.all_generated_frames) == 0:
        return None, None, None

    num_use = min(max_preceding, len(state.all_generated_frames))
    preceding_start_idx = len(state.all_generated_frames) - num_use
    preceding_frames = np.stack(state.all_generated_frames[preceding_start_idx:], axis=0)

    use_mp4_scene = bool(state.__dict__.get("use_mp4_scene", False))
    use_mp4_fg = bool(state.__dict__.get("use_mp4_fg", use_mp4_scene))
    blend_fg_into_scene = bool(state.__dict__.get("blend_fg_into_scene", False))
    scene_frames = state.__dict__.get("scene_proj_frames")
    fg_frames = state.__dict__.get("fg_proj_frames")

    preceding_pose_start = target_frame_indices[0] - len(preceding_frames)
    preceding_pose_start = max(0, preceding_pose_start)
    preceding_pose_indices = list(range(preceding_pose_start, target_frame_indices[0]))

    preceding_scene_proj = None
    preceding_fg_proj = None

    fg_blend_frames = None
    if (blend_fg_into_scene and fg_frames is not None
            and preceding_pose_indices):
        fg_blend_frames = subset_video_frames(
            fg_frames, preceding_pose_indices, output_size,
        )

    if use_mp4_scene and scene_frames is not None:
        if preceding_pose_indices:
            if fg_blend_frames is not None:
                scene_sub = subset_video_frames(
                    scene_frames, preceding_pose_indices, output_size,
                )
                blended = blend_fg_over_scene(scene_sub, fg_blend_frames)
                preceding_scene_proj = encode_proj_frames_to_latent(
                    frames_all=blended,
                    frame_indices=list(range(len(blended))),
                    output_size=output_size,
                    vae=pipeline.vae, device=pipeline.device, dtype=pipeline.dtype,
                )
            else:
                preceding_scene_proj = encode_proj_frames_to_latent(
                    frames_all=scene_frames,
                    frame_indices=preceding_pose_indices,
                    output_size=output_size,
                    vae=pipeline.vae, device=pipeline.device, dtype=pipeline.dtype,
                )

    if not use_mp4_scene and state.points_world is not None and preceding_pose_indices:
        preceding_scene_proj = render_scene_proj_latent(
            points_world=state.points_world,
            colors=state.colors,
            colored_mask=state.colored_mask,
            target_frame_indices=preceding_pose_indices,
            poses_c2w=state.poses_c2w,
            intrinsics=state.intrinsics,
            intrinsics_size=state.intrinsics_size,
            output_size=output_size,
            vae=pipeline.vae,
            device=pipeline.device,
            dtype=pipeline.dtype,
            renderer=state.__dict__.get("scene_proj_renderer", "splat2d"),
            splat_rect_size=state.__dict__.get("scene_proj_splat_rect_size", 10),
            fg_blend_frames=fg_blend_frames,
        )

    if use_mp4_fg and fg_frames is not None and preceding_pose_indices:
        preceding_fg_proj = encode_proj_frames_to_latent(
            frames_all=fg_frames,
            frame_indices=preceding_pose_indices,
            output_size=output_size,
            vae=pipeline.vae, device=pipeline.device, dtype=pipeline.dtype,
        )

    return preceding_frames, preceding_scene_proj, preceding_fg_proj