package indexDB

import (
	"fmt"
	"log"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"sync"

	"github.com/blevesearch/bleve/v2"
	"github.com/blevesearch/bleve/v2/search/query"

	"apigo.cc/go/cast"
)

const SystemUserID = "_system"

type IndexDBUnauthorized struct {
	fulltextPath string
	vectorPath   string
	embedding    func(text string) ([]float32, error)
	logger       *log.Logger

	fulltext *Engine
	vector   *Store

	mu sync.RWMutex
}

func GetDB(fulltextPath, vectorPath string, embedding func(string) ([]float32, error), logger *log.Logger) (*IndexDBUnauthorized, error) {
	if logger == nil {
		logger = log.Default()
	}

	db := &IndexDBUnauthorized{
		fulltextPath: fulltextPath,
		vectorPath:   vectorPath,
		embedding:    embedding,
		logger:       logger,
	}

	if fulltextPath != "" {
		if parent := filepath.Dir(fulltextPath); parent != "." {
			os.MkdirAll(parent, 0755)
		}
		fEngine, err := newFulltextEngine(fulltextPath)
		if err != nil {
			return nil, fmt.Errorf("init fulltext error: %w", err)
		}
		db.fulltext = fEngine
	}

	if vectorPath != "" && embedding != nil {
		if parent := filepath.Dir(vectorPath); parent != "." {
			os.MkdirAll(parent, 0755)
		}
		vStore, err := newVectorStore(Config{StorageDir: vectorPath})
		if err != nil {
			return nil, fmt.Errorf("init vector error: %w", err)
		}
		db.vector = vStore
	}

	return db, nil
}

func (db *IndexDBUnauthorized) Close() error {
	db.mu.Lock()
	defer db.mu.Unlock()
	if db.fulltext != nil {
		return db.fulltext.Close()
	}
	return nil
}

func (db *IndexDBUnauthorized) Auth(userId string) *IndexDB {
	return &IndexDB{
		db:     db,
		userId: userId,
	}
}

type IndexDB struct {
	db     *IndexDBUnauthorized
	userId string
}

func (idx *IndexDB) Add(id string, text string, metadata map[string]any, allowUsers []string) error {
	idx.db.mu.RLock()
	defer idx.db.mu.RUnlock()

	if idx.db.fulltext != nil {
		err := idx.db.fulltext.AddDocument(id, text, metadata, allowUsers)
		if err != nil {
			return fmt.Errorf("fulltext add: %w", err)
		}
	}

	if idx.db.embedding != nil && idx.db.vector != nil {
		vec, err := idx.db.embedding(text)
		if err != nil {
			return fmt.Errorf("embedding: %w", err)
		}
		coll, err := idx.db.vector.GetOrCreateCollection("main")
		if err != nil {
			return fmt.Errorf("vector collection: %w", err)
		}
		err = coll.AddRecord(id, vec, metadata, allowUsers)
		if err != nil {
			return fmt.Errorf("vector add: %w", err)
		}
	}
	return nil
}

func (idx *IndexDB) Remove(id string) error {
	idx.db.mu.RLock()
	defer idx.db.mu.RUnlock()

	if idx.db.fulltext != nil {
		err := idx.db.fulltext.RemoveDocument(id)
		if err != nil {
			return fmt.Errorf("fulltext remove: %w", err)
		}
	}

	if idx.db.vector != nil {
		coll, err := idx.db.vector.GetOrCreateCollection("main")
		if err == nil {
			_ = coll.DeleteRecord(id)
		}
	}
	return nil
}

func (idx *IndexDB) Search(idPrefix string, queryStr string, topK int, filter []Condition) ([]SearchResult, error) {
	idx.db.mu.RLock()
	defer idx.db.mu.RUnlock()

	var wg sync.WaitGroup
	var fResults []SearchResult
	var vResults []SearchResult
	var fErr, vErr error

	if idx.db.fulltext != nil {
		wg.Add(1)
		go func() {
			defer wg.Done()
			fResults, fErr = idx.db.fulltext.Search(idPrefix, queryStr, topK*5, idx.userId, filter)
		}()
	}

	if idx.db.vector != nil && idx.db.embedding != nil && queryStr != "" {
		wg.Add(1)
		go func() {
			defer wg.Done()
			vec, err := idx.db.embedding(queryStr)
			if err != nil {
				vErr = fmt.Errorf("embed query: %w", err)
				return
			}
			if len(vec) > 0 {
				coll, err := idx.db.vector.GetOrCreateCollection("main")
				if err == nil {
					vResults, vErr = coll.Search(vec, topK*5, idx.userId, idPrefix, filter)
				} else {
					vErr = err
				}
			}
		}()
	}

	wg.Wait()

	if fErr != nil {
		return nil, fmt.Errorf("fulltext search: %w", fErr)
	}
	if vErr != nil {
		return nil, fmt.Errorf("vector search: %w", vErr)
	}

	merged := mergeAndRRF(fResults, vResults, topK)

	// Patch content for vector-only results
	if idx.db.fulltext != nil {
		for i := range merged {
			if merged[i].Content == "" {
				q := query.NewDocIDQuery([]string{merged[i].ID})
				req := bleve.NewSearchRequest(q)
				req.Fields = []string{"content", "metadata"}
				res, _ := idx.db.fulltext.index.Search(req)
				if res != nil && len(res.Hits) > 0 {
					merged[i].Content, _ = res.Hits[0].Fields["content"].(string)
					// Metadata might also be missing if it was vector-only hit
					if merged[i].Metadata == nil {
						metaIfc := make(map[string]any)
						for k, v := range res.Hits[0].Fields {
							if strings.HasPrefix(k, "metadata.") {
								metaIfc[strings.TrimPrefix(k, "metadata.")] = v
							}
						}
						merged[i].Metadata = metaIfc
					}
				}
			}
		}
	}

	return merged, nil
}

func mergeAndRRF(fResults []SearchResult, vResults []SearchResult, topK int) []SearchResult {
	scores := make(map[string]float32)
	items := make(map[string]SearchResult)

	const k = 60

	for i, r := range fResults {
		items[r.ID] = r
		rank := float32(i + 1)
		scores[r.ID] += 1.0 / (k + rank)
	}

	for i, r := range vResults {
		if _, ok := items[r.ID]; !ok {
			items[r.ID] = r
		}
		rank := float32(i + 1)
		scores[r.ID] += 1.0 / (k + rank)
	}

	var merged []SearchResult
	for id, score := range scores {
		item := items[id]
		item.Score = score
		merged = append(merged, item)
	}

	sort.Slice(merged, func(i, j int) bool {
		return merged[i].Score > merged[j].Score
	})

	if len(merged) > topK {
		merged = merged[:topK]
	}
	return merged
}

func (idx *IndexDB) ScanDocuments(lastID string, limit int) ([]RawDocument, error) {
	idx.db.mu.RLock()
	defer idx.db.mu.RUnlock()

	if idx.db.fulltext == nil {
		return nil, fmt.Errorf("fulltext engine not initialized")
	}

	var q query.Query
	if lastID == "" {
		q = query.NewMatchAllQuery()
	} else {
		rq := query.NewTermRangeQuery(lastID, "")
		f := false
		rq.InclusiveMin = &f
		rq.SetField("id")
		q = rq
	}

	req := bleve.NewSearchRequest(q)
	req.Size = limit
	req.SortBy([]string{"id"}) 
	req.Fields = []string{"*"}

	res, err := idx.db.fulltext.index.Search(req)
	if err != nil {
		return nil, fmt.Errorf("scan search error: %w", err)
	}

	var docs []RawDocument
	for _, hit := range res.Hits {
		idVal, _ := hit.Fields["id"].(string)
		if idVal == "" {
			idVal = hit.ID
		}

		content, _ := hit.Fields["content"].(string)
		metaIfc := make(map[string]any)
		var allowUsers []string

		for k, v := range hit.Fields {
			if strings.HasPrefix(k, "metadata.") {
				metaIfc[strings.TrimPrefix(k, "metadata.")] = v
			} else if strings.HasPrefix(k, "U-") && k != "U-_system" {
				if cast.To[string](v) == "1" {
					allowUsers = append(allowUsers, strings.TrimPrefix(k, "U-"))
				}
			}
		}

		docs = append(docs, RawDocument{
			ID:         idVal,
			Text:       content,
			Metadata:   metaIfc,
			AllowUsers: allowUsers,
		})
	}

	return docs, nil
}

func evalCondition(metadata map[string]any, id string, idPrefix string, filters []Condition) bool {
	if idPrefix != "" && !strings.HasPrefix(id, idPrefix) {
		return false
	}
	for _, cond := range filters {
		val, ok := metadata[cond.Field]
		if !ok {
			return false
		}
		
		valStr := cast.To[string](val)
		condValStr := cast.To[string](cond.Value)
		valFloat := cast.To[float64](val)
		condValFloat := cast.To[float64](cond.Value)

		switch cond.Operator {
		case "eq", "=", "==":
			if valStr != condValStr { return false }
		case "gt", ">":
			if valFloat <= condValFloat { return false }
		case "lt", "<":
			if valFloat >= condValFloat { return false }
		case "ge", ">=":
			if valFloat < condValFloat { return false }
		case "le", "<=":
			if valFloat > condValFloat { return false }
		case "contains":
			if !strings.Contains(valStr, condValStr) { return false }
		case "in":
			found := false
			if arr, ok := cond.Value.([]any); ok {
				for _, item := range arr {
					if cast.To[string](item) == valStr {
						found = true
						break
					}
				}
			} else if arr, ok := cond.Value.([]string); ok {
				for _, item := range arr {
					if item == valStr {
						found = true
						break
					}
				}
			}
			if !found { return false }
		case "between":
			if arr, ok := cond.Value.([]any); ok && len(arr) == 2 {
				minV := cast.To[float64](arr[0])
				maxV := cast.To[float64](arr[1])
				if valFloat < minV || valFloat > maxV { return false }
			} else if arr, ok := cond.Value.([]float64); ok && len(arr) == 2 {
				if valFloat < arr[0] || valFloat > arr[1] { return false }
			}
		default:
			return false
		}
	}
	return true
}