"""Scoring utilities ported from chosun-projects."""


def issue_count_to_score(count: int) -> float:
    """Convert issue count to 0-1 score. Used by title and image_caption eval."""
    mapping = {0: 1.0, 1: 0.75, 2: 0.5, 3: 0.25}
    return mapping.get(count, 0.0)


def error_count_to_severity(count: int) -> str:
    """Convert error count to 7-tier severity. Used by body eval."""
    mapping = {0: "perfect", 1: "excellent", 2: "good", 3: "okay", 4: "fair", 5: "poor"}
    return mapping.get(count, "severe")


def severity_to_score(severity: str) -> float:
    """Convert severity label to 0-1 score."""
    mapping = {
        "perfect": 1.0,
        "excellent": 0.9,
        "good": 0.7,
        "okay": 0.5,
        "fair": 0.3,
        "poor": 0.1,
        "severe": 0.0,
    }
    return mapping.get(severity, 0.0)


def score_to_severity(score: float, tiers: int = 5) -> str:
    """Convert 0-1 score to severity label."""
    if tiers == 7:
        if score >= 0.95:
            return "perfect"
        elif score >= 0.8:
            return "excellent"
        elif score >= 0.6:
            return "good"
        elif score >= 0.4:
            return "okay"
        elif score >= 0.2:
            return "fair"
        elif score >= 0.05:
            return "poor"
        else:
            return "severe"
    else:  # tiers == 5
        if score >= 0.9:
            return "perfect"
        elif score >= 0.7:
            return "excellent"
        elif score >= 0.4:
            return "good"
        elif score >= 0.2:
            return "okay"
        else:
            return "poor"


def weighted_average(scores: dict[str, float], weights: dict[str, float]) -> float:
    """Compute weighted average of scores."""
    total = sum(scores.get(k, 0.0) * w for k, w in weights.items())
    return total


def compute_lcs(seq1: list[str], seq2: list[str]) -> list[tuple[int, int]]:
    """Compute Longest Common Subsequence. Returns list of (i, j) index pairs.

    Ported from chosun-projects proofread/eval/scoring.py.
    """
    m, n = len(seq1), len(seq2)
    dp = [[0] * (n + 1) for _ in range(m + 1)]

    for i in range(1, m + 1):
        for j in range(1, n + 1):
            if seq1[i - 1] == seq2[j - 1]:
                dp[i][j] = dp[i - 1][j - 1] + 1
            else:
                dp[i][j] = max(dp[i - 1][j], dp[i][j - 1])

    # Backtrack to find LCS indices
    result = []
    i, j = m, n
    while i > 0 and j > 0:
        if seq1[i - 1] == seq2[j - 1]:
            result.append((i - 1, j - 1))
            i -= 1
            j -= 1
        elif dp[i - 1][j] > dp[i][j - 1]:
            i -= 1
        else:
            j -= 1

    return list(reversed(result))


def find_diffs(
    original_tokens: list[str],
    corrected_tokens: list[str],
    lcs_pairs: list[tuple[int, int]],
) -> list[dict]:
    """Find differences between original and corrected using LCS alignment.

    Returns list of diffs with keys: orig_tokens, corrected_tokens,
    orig_start, orig_end, corr_start, corr_end.
    """
    diffs = []
    prev_i, prev_j = -1, -1

    for curr_i, curr_j in lcs_pairs:
        if curr_i > prev_i + 1 or curr_j > prev_j + 1:
            orig_slice = original_tokens[prev_i + 1 : curr_i]
            corr_slice = corrected_tokens[prev_j + 1 : curr_j]
            if orig_slice or corr_slice:
                diffs.append({
                    "orig_tokens": orig_slice,
                    "corrected_tokens": corr_slice,
                    "orig_start": prev_i + 1,
                    "orig_end": curr_i,
                    "corr_start": prev_j + 1,
                    "corr_end": curr_j,
                })
        prev_i, prev_j = curr_i, curr_j

    # Handle trailing differences
    orig_tail = original_tokens[prev_i + 1 :]
    corr_tail = corrected_tokens[prev_j + 1 :]
    if orig_tail or corr_tail:
        diffs.append({
            "orig_tokens": orig_tail,
            "corrected_tokens": corr_tail,
            "orig_start": prev_i + 1,
            "orig_end": len(original_tokens),
            "corr_start": prev_j + 1,
            "corr_end": len(corrected_tokens),
        })

    return diffs


def merge_adjacent_diffs(diffs: list[dict], max_gap: int = 2) -> list[dict]:
    """Merge adjacent diffs that are within max_gap tokens of each other."""
    if not diffs:
        return []
    merged = [diffs[0]]
    for d in diffs[1:]:
        prev = merged[-1]
        if d["orig_start"] - prev["orig_end"] <= max_gap:
            prev["orig_tokens"].extend(d["orig_tokens"])
            prev["corrected_tokens"].extend(d["corrected_tokens"])
            prev["orig_end"] = d["orig_end"]
            prev["corr_end"] = d["corr_end"]
        else:
            merged.append(d)
    return merged


def compute_proofread_metrics(
    original: str, golden: str, predicted: str
) -> dict[str, int | float]:
    """Compute proofread evaluation metrics using token-level LCS.

    Returns: {tp, fp, missing, redundant, precision, recall}
    """
    orig_tokens = original.split()
    gold_tokens = golden.split()
    pred_tokens = predicted.split()

    # Find golden diffs (what should have been corrected)
    gold_lcs = compute_lcs(orig_tokens, gold_tokens)
    gold_diffs = find_diffs(orig_tokens, gold_tokens, gold_lcs)
    gold_diffs = merge_adjacent_diffs(gold_diffs)

    # Find predicted diffs (what was actually corrected)
    pred_lcs = compute_lcs(orig_tokens, pred_tokens)
    pred_diffs = find_diffs(orig_tokens, pred_tokens, pred_lcs)
    pred_diffs = merge_adjacent_diffs(pred_diffs)

    # Compare diffs using 2-pass matching
    tp = 0
    fp = 0

    gold_by_start = {d["orig_start"]: d for d in gold_diffs}
    pred_by_start = {d["orig_start"]: d for d in pred_diffs}

    # 1st pass: exact orig_start position matching
    matched_gold = set()
    matched_pred = set()

    for start in set(gold_by_start.keys()) & set(pred_by_start.keys()):
        gold_corr = " ".join(gold_by_start[start]["corrected_tokens"])
        pred_corr = " ".join(pred_by_start[start]["corrected_tokens"])
        if gold_corr == pred_corr:
            tp += 1
        else:
            fp += 1
        matched_gold.add(start)
        matched_pred.add(start)

    # 2nd pass: content-based matching for unmatched diffs
    # Handles cases where merge_adjacent_diffs grouped differently due to
    # extra corrections shifting token positions.
    # Match if golden's orig_tokens are a subset of (or equal to) pred's orig_tokens
    # and the golden correction appears within the pred correction.
    unmatched_gold = [d for d in gold_diffs if d["orig_start"] not in matched_gold]
    unmatched_pred = [d for d in pred_diffs if d["orig_start"] not in matched_pred]

    for g in list(unmatched_gold):
        g_orig = " ".join(g["orig_tokens"])
        g_corr = " ".join(g["corrected_tokens"])

        candidates = []
        for p in unmatched_pred:
            p_orig = " ".join(p["orig_tokens"])
            p_corr = " ".join(p["corrected_tokens"])

            # Check if golden's original text is contained in pred's original text
            # (merge may have grouped more tokens together in pred)
            if g_orig in p_orig or p_orig in g_orig:
                # Check if the golden correction appears in pred correction
                if g_corr in p_corr:
                    candidates.append((p, True))   # correction matches
                else:
                    candidates.append((p, False))  # same spot, different correction

        if not candidates:
            continue

        # Prefer matching corrections, then closest position
        candidates.sort(key=lambda x: (not x[1], abs(x[0]["orig_start"] - g["orig_start"])))
        best, corr_matches = candidates[0]

        if corr_matches:
            tp += 1
        else:
            fp += 1

        unmatched_gold.remove(g)
        unmatched_pred.remove(best)

    missing = len(unmatched_gold)
    redundant = len(unmatched_pred)

    # Compute precision and recall
    # Default 100 only when nothing to correct AND nothing was corrected (perfect no-op)
    # Default 0 when there were things to correct but model did nothing, or vice versa
    no_golden = (tp + fp + missing) == 0   # nothing to correct
    no_pred = (tp + fp + redundant) == 0   # model corrected nothing

    if no_golden and no_pred:
        precision, recall = 100.0, 100.0  # perfect: nothing to fix, nothing changed
    else:
        precision = (tp / (tp + fp + redundant) * 100) if not no_pred else 0.0
        recall = (tp / (tp + fp + missing) * 100) if not no_golden else 0.0

    f1 = (2 * precision * recall / (precision + recall)) if (precision + recall) > 0 else 0.0

    return {
        "tp": tp,
        "fp": fp,
        "missing": missing,
        "redundant": redundant,
        "precision": precision,
        "recall": recall,
        "f1": f1,
    }