"""
Attribution module for EchoPrime interpretability.
All computation is on CPU — tensors are explicitly moved at entry points.
"""

import re
from dataclasses import dataclass, field
from typing import Optional

import torch
import torch.nn.functional as F
import numpy as np


# ── Data classes ──

@dataclass
class VideoScore:
    video_idx: int
    view_label: str
    view_idx: int
    mil_weight: float
    cosine_similarity: float
    combined_score: float
    dicom_path: Optional[str] = None

@dataclass
class PhraseAttribution:
    phrase: str
    section: str
    section_idx: int
    video_scores: list = field(default_factory=list)

@dataclass
class SectionAttribution:
    section: str
    section_idx: int
    mil_weights_per_video: np.ndarray
    similarities_per_video: np.ndarray
    combined_scores_per_video: np.ndarray
    ranked_video_indices: np.ndarray
    section_embedding: np.ndarray


# ── Constants ──

ALL_SECTIONS = [
    "Left Ventricle", "Resting Segmental Wall Motion Analysis",
    "Right Ventricle", "Left Atrium", "Right Atrium", "Atrial Septum",
    "Mitral Valve", "Aortic Valve", "Tricuspid Valve", "Pulmonic Valve",
    "Pericardium", "Aorta", "IVC", "Pulmonary Artery", "Pulmonary Veins",
    "Postoperative Findings",
]

COARSE_VIEWS = [
    'A2C', 'A3C', 'A4C', 'A5C', 'Apical_Doppler',
    'Doppler_Parasternal_Long', 'Doppler_Parasternal_Short',
    'Parasternal_Long', 'Parasternal_Short', 'SSN', 'Subcostal',
]


# ── Report parsing ──

def parse_report_to_phrases(report_text: str) -> list:
    blocks = report_text.split("[SEP]")
    results = []
    for block in blocks:
        block = block.strip()
        if not block:
            continue
        section_name = None
        content = block
        for sec in ALL_SECTIONS:
            if block.startswith(sec):
                section_name = sec
                content = block[len(sec):].lstrip(":").strip()
                break
        if section_name is None:
            for sec in ALL_SECTIONS:
                if sec.lower() in block.lower()[:len(sec) + 5]:
                    section_name = sec
                    idx = block.lower().find(sec.lower())
                    content = block[idx + len(sec):].lstrip(":").strip()
                    break
        if section_name is None:
            continue
        section_idx = ALL_SECTIONS.index(section_name)
        for phrase in _split_into_phrases(content):
            phrase = phrase.strip()
            if phrase and len(phrase) > 2:
                results.append(PhraseAttribution(phrase=phrase, section=section_name, section_idx=section_idx))
    return results


def _split_into_phrases(text: str) -> list:
    sentences = re.split(r'(?<=[a-z])\.\s+(?=[A-Z])', text)
    phrases = [s.strip().rstrip(".") for s in sentences if s.strip()]
    if not phrases:
        phrases = [p.strip() for p in re.split(r'\s{2,}', text) if p.strip()]
    if not phrases and text.strip():
        phrases = [text.strip()]
    return phrases


# ── Per-video attribution ──

def compute_section_attributions(
    study_embedding: torch.Tensor,
    candidate_embeddings: torch.Tensor,
    section_weights: np.ndarray,
    non_empty_sections,
    view_labels: list,
    dicom_paths=None,
    k: int = 50,
) -> dict:
    # Force everything to CPU
    study_embedding = study_embedding.cpu()
    candidate_embeddings = candidate_embeddings.cpu()

    video_embeddings = study_embedding[:, :512]
    view_encodings = study_embedding[:, 512:]
    n_videos = video_embeddings.shape[0]
    results = {}

    for s_dx, sec in enumerate(non_empty_sections):
        sec = str(sec)

        mil_weights = np.zeros(n_videos, dtype=np.float32)
        for v_idx in range(n_videos):
            view_idx = torch.where(view_encodings[v_idx] == 1)[0]
            if len(view_idx) > 0:
                mil_weights[v_idx] = section_weights[s_dx][view_idx[0].item()]

        mil_weights_t = torch.tensor(mil_weights, dtype=torch.float32)
        weighted = video_embeddings * mil_weights_t.unsqueeze(1)
        section_embedding = F.normalize(weighted.mean(dim=0), dim=0)

        video_emb_norm = F.normalize(video_embeddings, dim=1)
        per_video_sims = video_emb_norm @ candidate_embeddings.T
        topk_sims = torch.topk(per_video_sims, k=min(k, per_video_sims.shape[1]), dim=1)
        avg_topk_sim = topk_sims.values.mean(dim=1).numpy()

        combined = mil_weights * avg_topk_sim
        ranked = np.argsort(combined)[::-1]

        results[sec] = SectionAttribution(
            section=sec, section_idx=s_dx,
            mil_weights_per_video=mil_weights,
            similarities_per_video=avg_topk_sim,
            combined_scores_per_video=combined,
            ranked_video_indices=ranked.copy(),
            section_embedding=section_embedding.numpy(),
        )
    return results


def build_phrase_attributions(phrase_list, section_attributions, view_labels, dicom_paths=None, top_k=10):
    for pa in phrase_list:
        sec = pa.section
        if sec not in section_attributions:
            continue
        sa = section_attributions[sec]
        top_indices = sa.ranked_video_indices[:top_k]
        pa.video_scores = [
            VideoScore(
                video_idx=int(idx),
                view_label=view_labels[idx] if idx < len(view_labels) else "Unknown",
                view_idx=COARSE_VIEWS.index(view_labels[idx]) if view_labels[idx] in COARSE_VIEWS else -1,
                mil_weight=float(sa.mil_weights_per_video[idx]),
                cosine_similarity=float(sa.similarities_per_video[idx]),
                combined_score=float(sa.combined_scores_per_video[idx]),
                dicom_path=dicom_paths[idx] if dicom_paths and idx < len(dicom_paths) else None,
            )
            for idx in top_indices
        ]
    return phrase_list


# ── Serialization ──

def phrase_attribution_to_dict(pa):
    return {
        "phrase": pa.phrase, "section": pa.section, "section_idx": pa.section_idx,
        "video_scores": [
            {"video_idx": vs.video_idx, "view_label": vs.view_label,
             "mil_weight": round(vs.mil_weight, 4),
             "cosine_similarity": round(vs.cosine_similarity, 4),
             "combined_score": round(vs.combined_score, 4),
             "dicom_path": vs.dicom_path}
            for vs in pa.video_scores
        ],
    }

def section_attribution_to_dict(sa):
    return {
        "section": sa.section, "section_idx": sa.section_idx,
        "top_videos": [
            {"video_idx": int(idx),
             "mil_weight": round(float(sa.mil_weights_per_video[idx]), 4),
             "cosine_similarity": round(float(sa.similarities_per_video[idx]), 4),
             "combined_score": round(float(sa.combined_scores_per_video[idx]), 4)}
            for idx in sa.ranked_video_indices[:10]
        ],
    }