package bot

import (
	"context"
	"fmt"

	"queryorchestration/internal/database/repository"

	"github.com/google/uuid"
)

// BuildConversationHistory returns the last cfg.RecentTurns completed
// turns for the session as a flat slice of ConversationMessage entries
// in ascending ordinal order: each turn produces (user prompt, assistant
// completion). Plan §7 mapping table.
//
// An empty session returns a non-nil zero-length slice so the FastAPI
// payload emits "conversation_history": [] (the swagger requires a
// non-null array).
func (s *Service) BuildConversationHistory(ctx context.Context, sessionID uuid.UUID) ([]ConversationMessage, error) {
	rows, err := s.dbCfg.GetDBQueries().GetCompletedTurnsForSessionAscending(ctx, &repository.GetCompletedTurnsForSessionAscendingParams{
		SessionID: sessionID,
		TurnLimit: int32(s.cfg.RecentTurns), //nolint:gosec // RecentTurns is bounded [1, 5] by ChatbotConfig.Validate
	})
	if err != nil {
		return nil, fmt.Errorf("bot: list completed turns: %w", err)
	}
	out := make([]ConversationMessage, 0, len(rows)*2)
	for _, r := range rows {
		userMsg := ConversationMessage{
			Role:      "user",
			Content:   r.Prompt,
			Timestamp: r.CreatedAt.Time,
		}
		assistantContent := ""
		if r.Completion != nil {
			assistantContent = *r.Completion
		}
		assistantMsg := ConversationMessage{
			Role:      "assistant",
			Content:   assistantContent,
			Timestamp: r.CreatedAt.Time,
		}
		out = append(out, userMsg, assistantMsg)
	}
	return out, nil
}

// BuildChatScope assembles the ChatScope payload sent to FastAPI. Plan
// §7 mapping table:
//
//   - Stored doc ids ∪ folder-expanded doc ids; stored folder ids preserved.
//   - Plan §4 fallback: empty scope tables mean "all documents for the
//     client", with folders returning an empty list.
//
// All ids are returned as strings so the swagger's array-of-string
// schema matches without callers re-stringifying. Document deduplication
// is performed in-memory using a UUID set; folder ids are emitted in
// stable insertion order (sorted by SQL).
func (s *Service) BuildChatScope(ctx context.Context, sessionID uuid.UUID, clientID string) (ChatScope, error) {
	queries := s.dbCfg.GetDBQueries()

	storedDocs, err := queries.ListBotSessionDocumentsForSession(ctx, sessionID)
	if err != nil {
		return ChatScope{}, fmt.Errorf("bot: list session documents: %w", err)
	}
	storedFolders, err := queries.ListBotSessionFoldersForSession(ctx, sessionID)
	if err != nil {
		return ChatScope{}, fmt.Errorf("bot: list session folders: %w", err)
	}

	// Plan §4 fallback: empty scope tables → all client docs, no folders.
	if len(storedDocs) == 0 && len(storedFolders) == 0 {
		all, err := queries.ListDocumentsByClient(ctx, clientID)
		if err != nil {
			return ChatScope{}, fmt.Errorf("bot: list all client documents: %w", err)
		}
		docIDs := make([]string, 0, len(all))
		for _, row := range all {
			docIDs = append(docIDs, row.ID.String())
		}
		return ChatScope{DocumentIDs: docIDs, FolderIDs: []string{}}, nil
	}

	// Stored docs + folder-expansion. Dedup via set since a stored doc
	// may also live under a stored folder.
	seen := make(map[uuid.UUID]struct{}, len(storedDocs))
	docIDs := make([]string, 0, len(storedDocs))
	for _, id := range storedDocs {
		if _, dup := seen[id]; dup {
			continue
		}
		seen[id] = struct{}{}
		docIDs = append(docIDs, id.String())
	}

	for _, folderID := range storedFolders {
		expanded, err := queries.GetDocumentIDsInFolderTreeForClient(ctx, &repository.GetDocumentIDsInFolderTreeForClientParams{
			FolderID: folderID,
			ClientID: clientID,
		})
		if err != nil {
			return ChatScope{}, fmt.Errorf("bot: expand folder tree: %w", err)
		}
		for _, id := range expanded {
			if _, dup := seen[id]; dup {
				continue
			}
			seen[id] = struct{}{}
			docIDs = append(docIDs, id.String())
		}
	}

	folderIDs := make([]string, 0, len(storedFolders))
	for _, id := range storedFolders {
		folderIDs = append(folderIDs, id.String())
	}
	return ChatScope{DocumentIDs: docIDs, FolderIDs: folderIDs}, nil
}