// Heuristic metadata-suggestion HTTP handlers (see
// internal/storage/metadata_suggestions.go):
//
//	POST /api/documents/{id}/suggest-metadata
//	GET  /api/documents/{id}/suggest-metadata
//	POST /api/documents/{id}/suggest-metadata/{suggestionId}/reviewed
//
// All three are normal authenticated tenant actions (s.auth). Suggestions are
// rule-based (no LLM) and NON-binding: nothing here applies a suggested field —
// accepting one goes through the normal edit endpoints (PATCH title,
// tag-attach, ...). Ownership is enforced in the store layer (id+tenant_id).
package api

import (
	"errors"
	"net/http"
	"strconv"

	"archivdms/internal/audit"
	"archivdms/internal/storage"
)

// handleGenerateSuggestions handles POST /api/documents/{id}/suggest-metadata.
// Triggers a fresh heuristic suggestion run and returns the persisted result.
func (s *Server) handleGenerateSuggestions(w http.ResponseWriter, r *http.Request) {
	sess := sessionFromCtx(r.Context())
	if sess.TenantID == nil {
		writeError(w, http.StatusForbidden, "tenant context required")
		return
	}
	docID, err := strconv.ParseInt(r.PathValue("id"), 10, 64)
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid document id")
		return
	}
	docRef := strconv.FormatInt(docID, 10)

	// provider selects the suggestion engine: "heuristic" (default, rule-based,
	// always available) or "ollama" (external LLM, only when the tenant has it
	// enabled). On an Ollama failure there is NO silent fallback to heuristic —
	// the error is surfaced so the frontend knows which provider did not answer.
	provider := r.URL.Query().Get("provider")
	if provider == "" {
		provider = "heuristic"
	}

	var sug *storage.MetadataSuggestion
	switch provider {
	case "heuristic":
		sug, err = s.store.GenerateHeuristicSuggestions(r.Context(), docID, *sess.TenantID, &sess.UserID)
	case "ollama":
		cfg, cfgErr := s.store.GetOllamaConfig(r.Context(), *sess.TenantID)
		if cfgErr != nil {
			s.audlog.Log(audit.Entry{EventType: audit.EventSuggestionGenerated, Username: sess.Username, TenantID: sess.TenantID, DocumentID: docRef, Success: false, Detail: "suggest_metadata ollama config err:" + cfgErr.Error()})
			writeError(w, http.StatusInternalServerError, "load ollama config failed")
			return
		}
		if !cfg.Enabled {
			s.audlog.Log(audit.Entry{EventType: audit.EventSuggestionGenerated, Username: sess.Username, TenantID: sess.TenantID, DocumentID: docRef, Success: false, Detail: "suggest_metadata ollama not enabled"})
			writeError(w, http.StatusBadRequest, "ollama provider is not enabled for this tenant")
			return
		}
		sug, err = s.store.GenerateOllamaSuggestions(r.Context(), docID, *sess.TenantID, &sess.UserID, *cfg)
	case "naive_bayes":
		// Trained, dependency-free ML classifier (internal/classifier). Yields no
		// candidates for a kind whose model is untrained/below threshold — that is
		// not an error. Any real failure is surfaced (no silent fallback).
		sug, err = s.store.GenerateNaiveBayesSuggestions(r.Context(), docID, *sess.TenantID, &sess.UserID)
	default:
		writeError(w, http.StatusBadRequest, "unknown provider (use 'heuristic', 'ollama' or 'naive_bayes')")
		return
	}

	if err != nil {
		status := http.StatusInternalServerError
		if errors.Is(err, storage.ErrDocumentNotFound) {
			status = http.StatusNotFound
		} else if provider == "ollama" {
			// Ollama unreachable/timeout/bad-response: a dependency failure, not a
			// server bug. 502 signals "upstream provider failed".
			status = http.StatusBadGateway
		}
		s.audlog.Log(audit.Entry{EventType: audit.EventSuggestionGenerated, Username: sess.Username, TenantID: sess.TenantID, DocumentID: docRef, Success: false, Detail: "suggest_metadata provider:" + provider + " err:" + err.Error()})
		writeError(w, status, "generate metadata suggestions failed")
		return
	}
	s.audlog.Log(audit.Entry{
		EventType: audit.EventSuggestionGenerated, Username: sess.Username, TenantID: sess.TenantID,
		DocumentID: docRef, Success: true, Detail: "suggest_metadata provider:" + provider + " id:" + strconv.FormatInt(sug.ID, 10),
	})
	writeJSON(w, http.StatusOK, sug)
}

// handleGetLatestSuggestion handles GET /api/documents/{id}/suggest-metadata.
// Returns the most recent suggestion run for the document.
func (s *Server) handleGetLatestSuggestion(w http.ResponseWriter, r *http.Request) {
	sess := sessionFromCtx(r.Context())
	if sess.TenantID == nil {
		writeError(w, http.StatusForbidden, "tenant context required")
		return
	}
	docID, err := strconv.ParseInt(r.PathValue("id"), 10, 64)
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid document id")
		return
	}
	sug, err := s.store.GetLatestSuggestion(r.Context(), docID, *sess.TenantID)
	if err != nil {
		if errors.Is(err, storage.ErrSuggestionNotFound) {
			writeError(w, http.StatusNotFound, "no metadata suggestion found")
			return
		}
		writeError(w, http.StatusInternalServerError, "get metadata suggestion failed")
		return
	}
	writeJSON(w, http.StatusOK, sug)
}

// handleMarkSuggestionReviewed handles
// POST /api/documents/{id}/suggest-metadata/{suggestionId}/reviewed. Flags a
// suggestion as reviewed (the user acted on it in the UI). Which fields were
// accepted went through the normal edit endpoints, not this call.
func (s *Server) handleMarkSuggestionReviewed(w http.ResponseWriter, r *http.Request) {
	sess := sessionFromCtx(r.Context())
	if sess.TenantID == nil {
		writeError(w, http.StatusForbidden, "tenant context required")
		return
	}
	docID, err := strconv.ParseInt(r.PathValue("id"), 10, 64)
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid document id")
		return
	}
	suggestionID, err := strconv.ParseInt(r.PathValue("suggestionId"), 10, 64)
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid suggestion id")
		return
	}
	docRef := strconv.FormatInt(docID, 10)
	if err := s.store.MarkSuggestionReviewed(r.Context(), suggestionID, *sess.TenantID, sess.UserID); err != nil {
		status := http.StatusNotFound
		if !errors.Is(err, storage.ErrSuggestionNotFound) {
			status = http.StatusInternalServerError
		}
		s.audlog.Log(audit.Entry{EventType: audit.EventSuggestionGenerated, Username: sess.Username, TenantID: sess.TenantID, DocumentID: docRef, Success: false, Detail: "suggest_metadata_reviewed id:" + strconv.FormatInt(suggestionID, 10) + " err:" + err.Error()})
		writeError(w, status, "mark suggestion reviewed failed")
		return
	}
	s.audlog.Log(audit.Entry{
		EventType: audit.EventSuggestionGenerated, Username: sess.Username, TenantID: sess.TenantID,
		DocumentID: docRef, Success: true, Detail: "suggest_metadata_reviewed id:" + strconv.FormatInt(suggestionID, 10),
	})
	writeJSON(w, http.StatusOK, map[string]string{"status": "reviewed"})
}