import re


def grep_search(
    lines: list[str],
    keyword: str,
    case_sensitive: bool = False,
    context_lines: int = 3,
) -> list[dict]:
    flags = 0 if case_sensitive else re.IGNORECASE
    pattern = re.compile(re.escape(keyword), flags)
    results = []
    for idx, line in enumerate(lines):
        if pattern.search(line):
            ctx_start = max(0, idx - context_lines)
            ctx_end = min(len(lines), idx + context_lines + 1)
            context = lines[ctx_start:ctx_end]
            results.append(
                {
                    "line_number": idx + 1,
                    "matched_line": line,
                    "context": context,
                    "context_start": ctx_start + 1,
                    "keyword": keyword,
                }
            )
    return results


def chain_search(
    lines: list[str],
    keywords: list[str],
    context_lines: int = 3,
) -> list[dict]:
    if not keywords:
        return []

    results = grep_search(lines, keywords[0], context_lines=context_lines)

    for kw in keywords[1:]:
        pattern = re.compile(re.escape(kw), re.IGNORECASE)
        results = [r for r in results if pattern.search(r["matched_line"])]

    # Update keyword field to reflect all keywords in the chain
    for r in results:
        r["keyword"] = keywords[0]
    return results


def search_corpus(
    corpus: dict[str, list[str]],
    chain_queries: list[list[str]],
    max_hits_per_query: int = 10,
) -> list[dict]:
    seen: set[tuple] = set()
    all_hits: list[dict] = []

    def _collect(query: list[str], hits_from_search: list[dict], filename: str) -> None:
        for hit in hits_from_search[:max_hits_per_query]:
            key = (filename, hit["line_number"])
            if key in seen:
                continue
            seen.add(key)
            all_hits.append(
                {
                    "file": filename,
                    "line_number": hit["line_number"],
                    "matched_line": hit["matched_line"],
                    "context": hit["context"],
                    "context_start": hit["context_start"],
                    "keywords": query,
                }
            )

    for query in chain_queries:
        if not query:
            continue
        for filename, lines in corpus.items():
            hits = chain_search(lines, query)
            if hits:
                _collect(query, hits, filename)
            else:
                # Fallback: search each keyword separately when no same-line matches
                for kw in query:
                    _collect([kw], grep_search(lines, kw), filename)

    return all_hits