"""
indexer.py — Upserts parsed documents and embeddings into PostgreSQL.
"""

from __future__ import annotations

import hashlib
import json
import logging
from typing import Any

import asyncpg

from chunker import Chunk
from parser import ParsedDocument

logger = logging.getLogger(__name__)


def sha256(text: str) -> str:
    return hashlib.sha256(text.encode('utf-8')).hexdigest()


async def upsert_document(
    conn: asyncpg.Connection,
    doc: ParsedDocument,
    chunks: list[Chunk],
    embeddings: list[list[float]],
) -> str:
    """
    Upsert a document and its chunks atomically.

    Returns the document UUID.
    """
    content_hash = sha256(doc.content_raw)

    async with conn.transaction():
        # ---- Upsert document ----
        row = await conn.fetchrow(
            """
            INSERT INTO documents
                (path, title, content, content_hash, frontmatter, tags, aliases, word_count, indexed_at)
            VALUES ($1, $2, $3, $4, $5::jsonb, $6, $7, $8, now())
            ON CONFLICT (path) DO UPDATE SET
                title        = EXCLUDED.title,
                content      = EXCLUDED.content,
                content_hash = EXCLUDED.content_hash,
                frontmatter  = EXCLUDED.frontmatter,
                tags         = EXCLUDED.tags,
                aliases      = EXCLUDED.aliases,
                word_count   = EXCLUDED.word_count,
                indexed_at   = now()
            RETURNING id, (xmax = 0) AS inserted
            """,
            doc.path,
            doc.title,
            doc.content_raw,
            content_hash,
            json.dumps(doc.frontmatter),
            doc.tags,
            doc.aliases,
            doc.word_count,
        )
        doc_id: str = str(row['id'])
        is_new = row['inserted']
        logger.info('%s document %s (%s)', 'Inserted' if is_new else 'Updated', doc.path, doc_id)

        # ---- Delete stale chunks ----
        await conn.execute('DELETE FROM chunks WHERE document_id = $1', row['id'])

        # ---- Insert chunks + embeddings ----
        chunk_records = []
        for chunk, embedding in zip(chunks, embeddings):
            chunk_records.append((
                row['id'],
                chunk.chunk_index,
                chunk.content,
                chunk.token_count,
                embedding,
                json.dumps(chunk.metadata),
            ))

        await conn.executemany(
            """
            INSERT INTO chunks (document_id, chunk_index, content, token_count, embedding, metadata)
            VALUES ($1, $2, $3, $4, $5::vector, $6::jsonb)
            """,
            chunk_records,
        )
        logger.debug('Upserted %d chunks for document %s', len(chunk_records), doc.path)

        # ---- Upsert relations (WikiLinks) ----
        await conn.execute(
            'DELETE FROM relations WHERE source_doc_id = $1 AND relation_type = $2',
            row['id'],
            'wikilink',
        )
        if doc.wikilinks:
            relation_records = [
                (row['id'], link, 'wikilink')
                for link in doc.wikilinks
            ]
            await conn.executemany(
                """
                INSERT INTO relations (source_doc_id, target_path, relation_type)
                VALUES ($1, $2, $3)
                """,
                relation_records,
            )
            # Resolve targets that already exist in the vault
            await conn.execute(
                """
                UPDATE relations r
                SET target_doc_id = d.id
                FROM documents d
                WHERE r.source_doc_id = $1
                  AND r.relation_type = 'wikilink'
                  AND (d.path LIKE '%' || r.target_path || '%'
                    OR d.title = r.target_path
                    OR r.target_path = ANY(d.aliases))
                """,
                row['id'],
            )

    return doc_id


async def document_needs_reindex(conn: asyncpg.Connection, path: str, content_hash: str) -> bool:
    """Return True if the document is new or its content hash has changed."""
    row = await conn.fetchrow(
        'SELECT content_hash FROM documents WHERE path = $1',
        path,
    )
    if row is None:
        return True
    return row['content_hash'] != content_hash


async def delete_document(conn: asyncpg.Connection, path: str) -> None:
    """Remove a document and its cascaded chunks/relations."""
    result = await conn.execute('DELETE FROM documents WHERE path = $1', path)
    logger.info('Deleted document %s (%s)', path, result)