from __future__ import annotations
from supabase import create_client, Client
from datetime import datetime
import os


def _client() -> Client:
    return create_client(os.environ["SUPABASE_URL"], os.environ["SUPABASE_KEY"])


# ── ChunkResult: rich return type for similarity search ──────────────────────

class ChunkResult:
    """Holds chunk text, its page of origin, and source document."""
    __slots__ = ("text", "page_number", "doc_id")

    def __init__(self, text: str, page_number: int, doc_id: str):
        self.text        = text
        self.page_number = page_number
        self.doc_id      = doc_id

    # Behaves like a plain string so old code that does `"\n".join(chunks)` still works
    def __str__(self)  -> str: return self.text
    def __repr__(self) -> str: return f"ChunkResult(doc={self.doc_id[:8]}, page={self.page_number})"


def store_chunks(
    doc_id: str,
    user_id: str,
    chunks,                         # list[ChunkMeta] or list[str]
    embeddings: list[list[float]],
    expires_at: datetime,
) -> None:
    client = _client()
    rows = []
    for i, (chunk, embedding) in enumerate(zip(chunks, embeddings)):
        # Support both ChunkMeta objects (with .text/.page_number) and plain strings
        text        = chunk.text        if hasattr(chunk, "text")        else str(chunk)
        page_number = chunk.page_number if hasattr(chunk, "page_number") else 1
        rows.append({
            "doc_id":      doc_id,
            "user_id":     user_id,
            "chunk_text":  text,
            "embedding":   embedding,
            "chunk_index": i,
            "page_number": page_number,
            "expires_at":  expires_at.isoformat(),
        })
    # Insert in batches of 100 to avoid payload limits
    for i in range(0, len(rows), 100):
        client.table("chunks").insert(rows[i : i + 100]).execute()


def similarity_search(
    doc_id: str,
    query_embedding: list[float],
    top_k: int = 5,
) -> list[ChunkResult]:
    """Search a single document and return rich ChunkResult objects."""
    client = _client()
    result = client.rpc(
        "match_chunks",
        {
            "query_embedding": query_embedding,
            "doc_id_filter": doc_id,
            "match_count": top_k,
        },
    ).execute()
    return [
        ChunkResult(
            text        = r["chunk_text"],
            page_number = r.get("page_number", 1),
            doc_id      = str(r.get("doc_id", doc_id)),
        )
        for r in result.data
    ]


def similarity_search_multi(
    doc_ids: list[str],
    query_embedding: list[float],
    top_k: int = 20,
) -> list[ChunkResult]:
    """Search across multiple documents and return rich ChunkResult objects."""
    if not doc_ids:
        return []
    if len(doc_ids) == 1:
        return similarity_search(doc_ids[0], query_embedding, top_k)

    client = _client()
    result = client.rpc(
        "match_chunks_multi",
        {
            "query_embedding": query_embedding,
            "doc_ids_filter":  doc_ids,
            "match_count":     top_k,
        },
    ).execute()
    return [
        ChunkResult(
            text        = r["chunk_text"],
            page_number = r.get("page_number", 1),
            doc_id      = str(r["doc_id"]),
        )
        for r in result.data
    ]


def get_all_chunks(doc_id: str) -> list[ChunkResult]:
    """Return every chunk for a document in order, for full-context retrieval."""
    client = _client()
    result = (
        client.table("chunks")
        .select("chunk_text, page_number, doc_id")
        .eq("doc_id", doc_id)
        .order("chunk_index", desc=False)
        .execute()
    )
    return [
        ChunkResult(
            text        = r["chunk_text"],
            page_number = r.get("page_number", 1),
            doc_id      = str(r.get("doc_id", doc_id)),
        )
        for r in result.data
    ]


def get_all_chunks_multi(doc_ids: list[str]) -> list[ChunkResult]:
    """Return all chunks for multiple documents in document+chunk order."""
    if not doc_ids:
        return []
    client = _client()
    result = (
        client.table("chunks")
        .select("chunk_text, page_number, doc_id, chunk_index")
        .in_("doc_id", doc_ids)
        .order("doc_id", desc=False)
        .order("chunk_index", desc=False)
        .execute()
    )
    return [
        ChunkResult(
            text        = r["chunk_text"],
            page_number = r.get("page_number", 1),
            doc_id      = str(r["doc_id"]),
        )
        for r in result.data
    ]