package engine

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"log/slog"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"time"

	"github.com/local/glpi-neural-brain/internal/graph"
	"github.com/local/glpi-neural-brain/internal/model"
)

const researchEvidenceSchemaVersion = 1

type researchEvidenceRecord struct {
	SchemaVersion int                  `json:"schema_version"`
	SavedAt       time.Time            `json:"saved_at"`
	ContentSHA256 string               `json:"content_sha256"`
	Result        model.ResearchResult `json:"result"`
}

// queueResearchEvidence stores accepted full-text evidence outside graph.db.
// The graph node only keeps a small summary and a portable relative path, so
// the browser graph payload does not grow by the full page content.
func (e *Engine) queueResearchEvidence(result model.ResearchResult) (string, string, error) {
	if e.Persistence == nil || strings.TrimSpace(e.Cfg.DataDir) == "" {
		return "", "", fmt.Errorf("research evidence persistence is unavailable")
	}
	if !result.Fetched || !result.Relevant || strings.TrimSpace(result.Content) == "" || strings.TrimSpace(result.URL) == "" {
		return "", "", fmt.Errorf("research evidence is not an accepted full-text result")
	}
	hashBytes := sha256.Sum256([]byte(result.URL + "\x00" + result.Content))
	contentHash := hex.EncodeToString(hashBytes[:])
	id := graph.ID("external", result.URL)
	relPath := filepath.ToSlash(filepath.Join("research-evidence", strings.ToLower(id)+".json"))
	record := researchEvidenceRecord{SchemaVersion: researchEvidenceSchemaVersion, SavedAt: time.Now().UTC(), ContentSHA256: contentHash, Result: result}
	data, err := json.MarshalIndent(record, "", "  ")
	if err != nil {
		return "", "", fmt.Errorf("encode research evidence: %w", err)
	}
	absPath := filepath.Join(e.Cfg.DataDir, filepath.FromSlash(relPath))
	if _, err := e.Persistence.QueueFile(absPath, append(data, '\n'), 0o640); err != nil {
		return "", "", fmt.Errorf("queue research evidence %q: %w", absPath, err)
	}
	e.cacheResearchEvidence(relPath, record)
	return relPath, contentHash, nil
}

// researchEvidenceForSources reuses full-text evidence learned in earlier
// synthesis cycles when it is already linked to one of the selected sources.
// The knowledge model still has to confirm that the evidence closes a current
// gap; reuse never bypasses the consolidation or article quality gates.
func (e *Engine) researchEvidenceForSources(sources []articleSource) []model.ResearchResult {
	if len(sources) == 0 || strings.TrimSpace(e.Cfg.DataDir) == "" {
		return nil
	}
	sourceIDs := map[string]bool{}
	for _, source := range sources {
		sourceIDs[source.Node.ID] = true
	}
	snapshot := e.Graph.Snapshot()
	externalIDs := map[string]bool{}
	for _, edge := range snapshot.Edges {
		if edge.Status == "rejected" {
			continue
		}
		switch edge.Type {
		case "research_evidence":
			if sourceIDs[edge.Target] {
				externalIDs[edge.Source] = true
			}
		case "grounded_by":
			if sourceIDs[edge.Source] {
				externalIDs[edge.Target] = true
			}
		}
	}
	if len(externalIDs) == 0 {
		return nil
	}
	nodes := make([]model.Node, 0, len(externalIDs))
	filter := e.effectiveThinkingFilter()
	for _, node := range snapshot.Nodes {
		if externalIDs[node.ID] && node.Kind == "external" && filter.Matches(node) {
			nodes = append(nodes, node)
		}
	}
	sort.SliceStable(nodes, func(i, j int) bool {
		if nodes[i].Weight == nodes[j].Weight {
			return nodes[i].ID < nodes[j].ID
		}
		return nodes[i].Weight > nodes[j].Weight
	})
	limit := e.Cfg.ArticleResearchResults * 2
	if limit < 8 {
		limit = 8
	}
	if limit > 24 {
		limit = 24
	}
	out := make([]model.ResearchResult, 0, min(limit, len(nodes)))
	for _, node := range nodes {
		if len(out) >= limit {
			break
		}
		relPath := metadataString(node.Metadata, "evidence_path")
		if relPath == "" {
			continue
		}
		record, err := e.loadResearchEvidence(relPath)
		if err != nil {
			slog.Warn("stored research evidence could not be reused", "node_id", node.ID, "path", relPath, "error", err)
			continue
		}
		result := record.Result
		if result.Relevance < e.Cfg.ArticleResearchMinRelevance || result.SourceQualityScore < e.Cfg.ArticleResearchMinQuality {
			continue
		}
		out = append(out, result)
	}
	return uniqueResearchEvidence(out)
}

func (e *Engine) loadResearchEvidence(relPath string) (researchEvidenceRecord, error) {
	var record researchEvidenceRecord
	clean := filepath.Clean(filepath.FromSlash(strings.TrimSpace(relPath)))
	if clean == "." || clean == "" || filepath.IsAbs(clean) || clean == ".." || strings.HasPrefix(clean, ".."+string(filepath.Separator)) {
		return record, fmt.Errorf("unsafe research evidence path %q", relPath)
	}
	cacheKey := filepath.ToSlash(clean)
	if cached, ok := e.cachedResearchEvidence(cacheKey); ok {
		return cached, nil
	}
	root, err := filepath.Abs(e.Cfg.DataDir)
	if err != nil {
		return record, fmt.Errorf("resolve data directory: %w", err)
	}
	path := filepath.Join(root, clean)
	rel, err := filepath.Rel(root, path)
	if err != nil || rel == ".." || strings.HasPrefix(rel, ".."+string(filepath.Separator)) {
		return record, fmt.Errorf("research evidence path escapes data directory")
	}
	data, err := os.ReadFile(path)
	if err != nil {
		return record, err
	}
	if err := json.Unmarshal(data, &record); err != nil {
		return record, fmt.Errorf("decode research evidence: %w", err)
	}
	if record.SchemaVersion != researchEvidenceSchemaVersion {
		return record, fmt.Errorf("unsupported research evidence schema %d", record.SchemaVersion)
	}
	if !record.Result.Fetched || !record.Result.Relevant || strings.TrimSpace(record.Result.Content) == "" || strings.TrimSpace(record.Result.URL) == "" {
		return record, fmt.Errorf("stored research evidence is incomplete")
	}
	hashBytes := sha256.Sum256([]byte(record.Result.URL + "\x00" + record.Result.Content))
	if record.ContentSHA256 == "" || !strings.EqualFold(record.ContentSHA256, hex.EncodeToString(hashBytes[:])) {
		return record, fmt.Errorf("stored research evidence checksum mismatch")
	}
	e.cacheResearchEvidence(cacheKey, record)
	return record, nil
}

func (e *Engine) cacheResearchEvidence(key string, record researchEvidenceRecord) {
	key = filepath.ToSlash(filepath.Clean(filepath.FromSlash(strings.TrimSpace(key))))
	if key == "." || key == "" {
		return
	}
	e.researchEvidenceMu.Lock()
	if e.researchEvidenceCache == nil {
		e.researchEvidenceCache = map[string]researchEvidenceRecord{}
	}
	e.researchEvidenceCache[key] = record
	e.researchEvidenceMu.Unlock()
}

func (e *Engine) cachedResearchEvidence(key string) (researchEvidenceRecord, bool) {
	e.researchEvidenceMu.RLock()
	record, ok := e.researchEvidenceCache[key]
	e.researchEvidenceMu.RUnlock()
	return record, ok
}

// learnResearchEvidence embeds newly accepted external evidence immediately.
// It is still persisted by the normal batched graph flush, but becomes usable
// for semantic placement and later relations in the current process at once.
func (e *Engine) learnResearchEvidence(ctx context.Context, results []model.ResearchResult) {
	if !e.LearningEnabled() || len(results) == 0 || e.Ollama == nil {
		return
	}
	ids := make([]string, 0, len(results))
	texts := make([]string, 0, len(results))
	for _, result := range results {
		id := graph.ID("external", result.URL)
		node, ok := e.Graph.GetNode(id)
		if !ok || !e.effectiveLearningFilter().Matches(node) {
			continue
		}
		content := strings.TrimSpace(result.Content)
		if content == "" {
			content = node.Summary
		}
		text := strings.TrimSpace(result.Title + "\n" + clamp(content, 6000))
		if text == "" {
			continue
		}
		ids = append(ids, id)
		texts = append(texts, text)
	}
	if len(ids) == 0 {
		return
	}
	vectors, err := e.Ollama.Embed(ctx, texts)
	fallback := err != nil || len(vectors) != len(ids)
	if !fallback {
		for _, vector := range vectors {
			if len(vector) == 0 {
				fallback = true
				break
			}
		}
	}
	if fallback {
		for i, id := range ids {
			e.Graph.SetVector(id, hashEmbedding(texts[i], 256))
		}
		e.Broker.Publish(model.Activity{Type: "article.research.learned", Source: "brain", Phase: "embedding", NodeIDs: ids, Message: fmt.Sprintf("%d geprüfte Webbelege wurden mit lokalen Fallback-Vektoren gelernt", len(ids)), Strength: .48, Metadata: map[string]any{"result_count": len(ids), "fallback": true, "error": errorString(err)}})
		return
	}
	for i, id := range ids {
		e.Graph.SetVector(id, vectors[i])
	}
	e.Broker.Publish(model.Activity{Type: "article.research.learned", Source: "ollama", Phase: "embedding", NodeIDs: ids, Message: fmt.Sprintf("%d geprüfte Volltextbelege wurden eingebettet und sind semantisch nutzbar", len(ids)), Strength: .72, Metadata: map[string]any{"result_count": len(ids), "model": e.Cfg.EmbeddingModel, "dimensions": len(vectors[0])}})
}

func errorString(err error) string {
	if err == nil {
		return ""
	}
	return err.Error()
}