package session

import (
	"database/sql"
	"fmt"
	"strings"
)

type VectorStore struct {
	db      *sql.DB
	enabled bool
}

func NewVectorStore(db *sql.DB) (*VectorStore, error) {
	vs := &VectorStore{db: db}
	if err := vs.initSchema(); err != nil {
		return &VectorStore{db: db, enabled: false}, nil
	}
	vs.enabled = true
	return vs, nil
}

func (vs *VectorStore) initSchema() error {
	_, err := vs.db.Exec(`
		CREATE VIRTUAL TABLE IF NOT EXISTS vec_main_messages USING vec0(
			msg_id INTEGER PRIMARY KEY,
			embedding FLOAT[1024]
		)
	`)
	return err
}

func (vs *VectorStore) SaveEmbedding(msgID int64, embedding []float32) error {
	if !vs.enabled {
		return nil
	}

	if len(embedding) != 1024 {
		return fmt.Errorf("expected 1024 dimensions, got %d", len(embedding))
	}

	embeddingStr := formatEmbedding(embedding)
	_, err := vs.db.Exec(
		"INSERT INTO vec_main_messages (msg_id, embedding) VALUES (?, ?)",
		msgID, embeddingStr,
	)
	if err != nil {
		return fmt.Errorf("failed to save embedding: %w", err)
	}

	_, err = vs.db.Exec(
		"UPDATE main_messages SET has_embedding = TRUE WHERE id = ?",
		msgID,
	)
	return err
}

func (vs *VectorStore) SaveLongTermEmbedding(memoryID int64, embedding []float32) error {
	if !vs.enabled {
		return nil
	}

	if len(embedding) != 1024 {
		return fmt.Errorf("expected 1024 dimensions, got %d", len(embedding))
	}

	embeddingStr := formatEmbedding(embedding)
	_, err := vs.db.Exec(
		"INSERT INTO vec_long_term_memories (memory_id, embedding) VALUES (?, ?)",
		memoryID, embeddingStr,
	)
	if err != nil {
		return fmt.Errorf("failed to save long-term embedding: %w", err)
	}
	return nil
}

func (vs *VectorStore) SearchLongTermSimilar(embedding []float32, limit int) ([]struct {
	MemoryID int64
	Distance float64
}, error) {
	if !vs.enabled {
		return nil, nil
	}

	if len(embedding) != 1024 {
		return nil, fmt.Errorf("expected 1024 dimensions, got %d", len(embedding))
	}

	embeddingStr := formatEmbedding(embedding)
	rows, err := vs.db.Query(
		`SELECT memory_id, distance FROM vec_long_term_memories
		WHERE embedding MATCH ?
		ORDER BY distance
		LIMIT ?`,
		embeddingStr, limit,
	)
	if err != nil {
		return nil, fmt.Errorf("failed to search long-term vectors: %w", err)
	}
	defer rows.Close()

	var results []struct {
		MemoryID int64
		Distance float64
	}
	for rows.Next() {
		var r struct {
			MemoryID int64
			Distance float64
		}
		if err := rows.Scan(&r.MemoryID, &r.Distance); err != nil {
			return nil, err
		}
		results = append(results, r)
	}

	return results, rows.Err()
}

func (vs *VectorStore) SearchSimilar(embedding []float32, limit int) ([]int64, error) {
	if !vs.enabled {
		return []int64{}, nil
	}

	if len(embedding) != 1024 {
		return nil, fmt.Errorf("expected 1024 dimensions, got %d", len(embedding))
	}

	embeddingStr := formatEmbedding(embedding)
	rows, err := vs.db.Query(
		`SELECT msg_id FROM vec_main_messages
		WHERE embedding MATCH ?
		ORDER BY distance
		LIMIT ?`,
		embeddingStr, limit,
	)
	if err != nil {
		return nil, fmt.Errorf("failed to search vectors: %w", err)
	}
	defer rows.Close()

	var msgIDs []int64
	for rows.Next() {
		var id int64
		if err := rows.Scan(&id); err != nil {
			return nil, err
		}
		msgIDs = append(msgIDs, id)
	}

	return msgIDs, rows.Err()
}

func (vs *VectorStore) SearchSimilarInSession(sessionID string, embedding []float32, limit int) ([]int64, error) {
	if !vs.enabled {
		return []int64{}, nil
	}

	if len(embedding) != 1024 {
		return nil, fmt.Errorf("expected 1024 dimensions, got %d", len(embedding))
	}

	embeddingStr := formatEmbedding(embedding)
	rows, err := vs.db.Query(
		`SELECT v.msg_id FROM vec_main_messages v
		JOIN main_messages m ON v.msg_id = m.id
		WHERE m.session_id = ? AND v.embedding MATCH ?
		ORDER BY distance
		LIMIT ?`,
		sessionID, embeddingStr, limit,
	)
	if err != nil {
		return nil, fmt.Errorf("failed to search session vectors: %w", err)
	}
	defer rows.Close()

	var msgIDs []int64
	for rows.Next() {
		var id int64
		if err := rows.Scan(&id); err != nil {
			return nil, err
		}
		msgIDs = append(msgIDs, id)
	}

	return msgIDs, rows.Err()
}

func formatEmbedding(embedding []float32) string {
	parts := make([]string, len(embedding))
	for i, v := range embedding {
		parts[i] = fmt.Sprintf("%f", v)
	}
	return "[" + strings.Join(parts, ",") + "]"
}