package rag

import (
	"context"
	"encoding/json"
	"fmt"
	"log"
	"strings"

	"github.com/neo4j/neo4j-go-driver/v5/neo4j"
	"github.com/neo4j/neo4j-go-driver/v5/neo4j/auth"
)

// Triple 是一条知识三元组（主体-关系-客体）。
type Triple struct {
	S string `json:"s"`
	P string `json:"p"`
	O string `json:"o"`
}

// graphStore 是 GraphRAG 的图路：实体/关系存 Neo4j。
type graphStore struct {
	driver neo4j.DriverWithContext
}

func openGraph(ctx context.Context, uri, user, pass string) *graphStore {
	if uri == "" {
		return &graphStore{}
	}
	drv, err := neo4j.NewDriverWithContext(uri,
		auth.BasicTokenManager(func(context.Context) (neo4j.AuthToken, error) {
			return neo4j.BasicAuth(user, pass, ""), nil
		}))
	if err != nil {
		log.Printf("[rag] Neo4j 连接失败，图谱路降级: %v", err)
		return &graphStore{}
	}
	if err := drv.VerifyConnectivity(ctx); err != nil {
		log.Printf("[rag] Neo4j 不可用，图谱路降级: %v", err)
		return &graphStore{}
	}
	// 实体唯一约束（kb+name）。
	_, _ = neo4j.ExecuteQuery(ctx, drv,
		"CREATE CONSTRAINT entity_key IF NOT EXISTS FOR (e:Entity) REQUIRE (e.kb, e.name) IS UNIQUE",
		nil, neo4j.EagerResultTransformer)
	log.Printf("[rag] Neo4j connected %s", uri)
	return &graphStore{driver: drv}
}

func (g *graphStore) ready() bool { return g != nil && g.driver != nil }

func (g *graphStore) close(ctx context.Context) {
	if g.ready() {
		_ = g.driver.Close(ctx)
	}
}

// store 把三元组 MERGE 进 Neo4j（实体 + 关系，按 kb 隔离）。
func (g *graphStore) store(ctx context.Context, kb string, triples []Triple) (int, error) {
	if !g.ready() {
		return 0, nil
	}
	n := 0
	for _, t := range triples {
		if t.S == "" || t.O == "" || t.P == "" {
			continue
		}
		_, err := neo4j.ExecuteQuery(ctx, g.driver,
			`MERGE (a:Entity {kb:$kb, name:$s})
			 MERGE (b:Entity {kb:$kb, name:$o})
			 MERGE (a)-[r:REL {type:$p}]->(b)`,
			map[string]any{"kb": kb, "s": t.S, "o": t.O, "p": t.P},
			neo4j.EagerResultTransformer, neo4j.ExecuteQueryWithDatabase("neo4j"))
		if err != nil {
			return n, err
		}
		n++
	}
	return n, nil
}

// search 图谱召回：找查询里提到的实体，返回其相连三元组（文本化）。
func (g *graphStore) search(ctx context.Context, kb, query string, limit int) []Hit {
	if !g.ready() || query == "" {
		return nil
	}
	res, err := neo4j.ExecuteQuery(ctx, g.driver,
		`MATCH (a:Entity {kb:$kb})-[r:REL]->(b:Entity {kb:$kb})
		 WHERE $q CONTAINS a.name OR $q CONTAINS b.name
		 RETURN a.name AS s, r.type AS p, b.name AS o LIMIT $k`,
		map[string]any{"kb": kb, "q": query, "k": limit},
		neo4j.EagerResultTransformer, neo4j.ExecuteQueryWithDatabase("neo4j"))
	if err != nil {
		return nil
	}
	var hits []Hit
	for _, rec := range res.Records {
		s, _ := rec.Get("s")
		p, _ := rec.Get("p")
		o, _ := rec.Get("o")
		hits = append(hits, Hit{Text: fmt.Sprintf("%v —%v→ %v", s, p, o), Score: 1})
	}
	return hits
}

// triples 返回某 kb 的全部三元组（供 UI 图谱可视化）。
func (g *graphStore) triples(ctx context.Context, kb string, limit int) []Triple {
	if !g.ready() {
		return nil
	}
	res, err := neo4j.ExecuteQuery(ctx, g.driver,
		`MATCH (a:Entity {kb:$kb})-[r:REL]->(b:Entity {kb:$kb})
		 RETURN a.name AS s, r.type AS p, b.name AS o LIMIT $k`,
		map[string]any{"kb": kb, "k": limit},
		neo4j.EagerResultTransformer, neo4j.ExecuteQueryWithDatabase("neo4j"))
	if err != nil {
		return nil
	}
	var out []Triple
	for _, rec := range res.Records {
		s, _ := rec.Get("s")
		p, _ := rec.Get("p")
		o, _ := rec.Get("o")
		out = append(out, Triple{S: fmt.Sprint(s), P: fmt.Sprint(p), O: fmt.Sprint(o)})
	}
	return out
}

// extractTriples 用 LLM 从文本抽取知识三元组。
func extractTriples(ctx context.Context, chat *chatClient, text string) ([]Triple, error) {
	if !chat.ready() {
		return nil, nil
	}
	const sys = "你是知识图谱抽取器。从用户文本中抽取知识三元组，输出 JSON 数组，每项形如 {\"s\":\"主体\",\"p\":\"关系\",\"o\":\"客体\"}。实体用简洁名词，关系用简短动词短语。只输出 JSON，不要任何解释或代码块标记。"
	out, err := chat.complete(ctx, sys, text)
	if err != nil {
		return nil, err
	}
	return parseTriples(out), nil
}

// parseTriples 容忍代码块/前后噪声地解析三元组 JSON。
func parseTriples(s string) []Triple {
	s = strings.TrimSpace(s)
	s = strings.TrimPrefix(s, "```json")
	s = strings.TrimPrefix(s, "```")
	s = strings.TrimSuffix(s, "```")
	if i := strings.Index(s, "["); i >= 0 {
		if j := strings.LastIndex(s, "]"); j > i {
			s = s[i : j+1]
		}
	}
	var triples []Triple
	if json.Unmarshal([]byte(s), &triples) != nil {
		return nil
	}
	return triples
}