import { createClient, SupabaseClient, PostgrestError } from '@supabase/supabase-js';
import type { Flyer, FlyerItem, MasterGroceryItem, Profile, ShoppingList, ShoppingListItem, Store, SuggestedCorrection, UnitPrice } from '../types';
import { logger } from './logger';
import { Database, Json } from '../types/supabase';

// In a Vite project, environment variables are exposed on the `import.meta.env` object.
// For security, only variables prefixed with `VITE_` are exposed to the client-side code.
const supabaseUrl = import.meta.env.VITE_SUPABASE_URL;
const supabaseAnonKey = import.meta.env.VITE_SUPABASE_ANON_KEY;

if (!supabaseUrl || !supabaseAnonKey) {
  console.warn("Supabase environment variables not set. Running in no-database mode.");
}

// Create and export the Supabase client.
// If the keys are missing, this will be null, and features requiring it will be disabled.
export let supabase = (supabaseUrl && supabaseAnonKey) 
  ? createClient<Database>(supabaseUrl, supabaseAnonKey)
  : null;

// =============================================
// INTERNAL HELPERS
// =============================================

/**
 * Initializes or re-initializes the Supabase client with new credentials.
 * This is used for manual connection from the UI.
 * @param url The Supabase project URL.
 * @param anonKey The Supabase anon key.
 * @returns The newly created Supabase client instance.
 */
export const initializeSupabase = (url: string, anonKey: string): SupabaseClient<Database> => {
    if (!url || !anonKey) {
        throw new Error("Supabase URL and Anon Key are required.");
    }
    supabase = createClient<Database>(url, anonKey);
    return supabase;
};

/**
 * A centralized check to ensure the Supabase client is initialized before use.
 * @throws {Error} If the client is not initialized.
 */
const ensureSupabase = (): SupabaseClient<Database> => {
    if (!supabase) {
        throw new Error("Supabase client not initialized. Please check your environment variables and configuration.");
    }
    return supabase;
};

/**
 * Generic helper to handle Supabase query responses, centralizing error handling and data casting.
 * @param query A Supabase query promise.
 * @returns The data from the query, or throws an error.
 */
const handleResponse = async <T>(query: PromiseLike<{
    data: T | null;
    error: PostgrestError | null;
}>): Promise<T | null> => {
    const { data, error } = await query;
    if (error) throw new Error(error.message);
    return data;
};

/**
 * A type guard to check if a given JSON object conforms to the UnitPrice interface.
 * This provides runtime validation to safely cast the generic `Json` type from
 * Supabase to our specific application `UnitPrice` type.
 * @param obj The object to check.
 * @returns True if the object is a valid UnitPrice, false otherwise.
 */
const isUnitPrice = (obj: unknown): obj is UnitPrice => {
    return (
        typeof obj === 'object' && obj !== null && 'value' in obj && 'unit' in obj && typeof (obj as UnitPrice).value === 'number' && typeof (obj as UnitPrice).unit === 'string'
    );
};

/**
 * Disconnects the Supabase client by setting the instance to null.
 */
export const disconnectSupabase = (): void => {
    supabase = null;
    // Clear stored credentials on explicit disconnect
    localStorage.removeItem('supabaseUrl');
    localStorage.removeItem('supabaseAnonKey');
};

/**
 * Tests basic read access to the database.
 * @returns An object indicating success and any error message.
 */
export const testDatabaseConnection = async (): Promise<{ success: boolean; error: string | null }> => {
    try {
        const { error } = await ensureSupabase().from('stores').select('id').limit(1);
        if (error) throw error;
        return { success: true, error: null };
    } catch (error) {
        const errorMessage = error instanceof Error ? error.message : String(error);
        return { success: false, error: `Database connection test failed: ${errorMessage}. Check RLS policies and client initialization.` };
    }
};

/**
 * Performs a full CRUD (Create, Read, Update, Delete) test on a table.
 * @returns An object indicating success and any error message.
 */
export const runDatabaseSelfTest = async (): Promise<{ success: boolean; error: string | null }> => {
    const supabaseClient = ensureSupabase();

    const testItem = {
        item: `DB_SELF_TEST_ITEM_${Date.now()}`,
        price_display: '$0.00',
        quantity: 'test',
    };

    try {
        // 1. Insert
        const { data: insertData, error: insertError } = await supabaseClient
            .from('flyer_items')
            .insert(testItem)
            .select()
            .single();
        if (insertError) throw new Error(`Insert failed: ${insertError.message}`);
        if (!insertData) throw new Error('Insert did not return data.');

        // 2. Select (implicit in insert's .select())
        const testItemId = insertData.id;

        // 3. Update
        const { error: updateError } = await supabaseClient
            .from('flyer_items')
            .update({ item: 'DB_SELF_TEST_ITEM_UPDATED' })
            .eq('id', testItemId);
        if (updateError) throw new Error(`Update failed: ${updateError.message}`);

        // 4. Delete
        const { error: deleteError } = await supabaseClient
            .from('flyer_items')
            .delete()
            .eq('id', testItemId);
        if (deleteError) throw new Error(`Delete failed: ${deleteError.message}`);

        return { success: true, error: null };
    } catch (error) {
        const errorMessage = error instanceof Error ? error.message : String(error);
        return { success: false, error: `Database self-test failed: ${errorMessage}. Check table permissions (select, insert, update, delete) and RLS policies for 'flyer_items'.` };
    }
};

/**
 * Tests storage by uploading and deleting a file.
 * @returns An object indicating success and any error message.
 */
export const testStorageConnection = async (): Promise<{ success: boolean; error: string | null }> => {
    const supabaseClient = ensureSupabase();
    
    const bucketName = 'flyers';
    const testFileName = `storage-self-test-${Date.now()}.txt`;
    const testFileContent = 'test';

    try {
        // 1. Upload
        const { error: uploadError } = await supabaseClient.storage
            .from(bucketName)
            .upload(testFileName, testFileContent);
        if (uploadError) throw new Error(`Upload to storage failed: ${uploadError.message}`);
        
        // 2. Delete
        const { error: deleteError } = await supabaseClient.storage
            .from(bucketName)
            .remove([testFileName]);
        if (deleteError) throw new Error(`Deleting from storage failed: ${deleteError.message}`);

        return { success: true, error: null };
    } catch (error) {
        const errorMessage = error instanceof Error ? error.message : String(error);
        return { success: false, error: `Storage connection test failed: ${errorMessage}. Check bucket permissions (select, insert, delete) and RLS policies for bucket '${bucketName}'.` };
    }
};

/**
 * Uploads a flyer image to Supabase storage.
 * @param file The image file to upload.
 * @returns The public URL of the uploaded image.
 */
export const uploadFlyerImage = async (file: File): Promise<string> => {
    const supabaseClient = ensureSupabase();
    
    const fileName = `${Date.now()}-${file.name.replace(/[^a-zA-Z0-9.-]/g, '_')}`;
    const { data: uploadData, error } = await supabaseClient.storage
        .from('flyers')
        .upload(fileName, file);
    if (error) throw new Error(`Failed to upload flyer image: ${error.message}`);
    if (!uploadData) throw new Error("Upload did not return a path.");

    const { data: urlData } = supabaseClient.storage.from('flyers').getPublicUrl(uploadData.path);
    const publicUrl = urlData?.publicUrl;
    if (!publicUrl) throw new Error("Could not get public URL for uploaded flyer image.");
    
    return publicUrl;
};

/**
 * Creates a record for a new flyer in the database, handling store creation if needed.
 * @returns The newly created flyer object, joined with its store.
 */
export const createFlyerRecord = async (
    fileName: string,
    imageUrl: string,
    checksum: string,
    storeName: string,
    validFrom: string | null,
    validTo: string | null,
    storeAddress: string | null
): Promise<Flyer> => {
    const supabaseClient = ensureSupabase();

    let store = await handleResponse<Store>(
        supabaseClient
        .from('stores')
        .select('*')
        .ilike('name', storeName)
        .maybeSingle()
    );

    if (!store) {
        store = await handleResponse(supabaseClient
            .from('stores')
            .insert({ name: storeName })
            .select()
            .single());
    }

    const { data: newFlyer, error: flyerError } = await supabase
        .from('flyers')
        .insert({
            file_name: fileName,
            image_url: imageUrl,
            checksum: checksum,
            store_id: store.id,
            valid_from: validFrom,
            valid_to: validTo,
            store_address: storeAddress,
        })
        .select('*, store:stores(*)')
        .single();
    
    if (flyerError) throw new Error(`Failed to create flyer record: ${flyerError.message}`);
    if (!newFlyer) throw new Error("Flyer record creation did not return data.");

    return newFlyer as Flyer;
};

/**
 * Saves a list of extracted items to the database.
 * @param items The items to save.
 * @param flyerId The ID of the flyer these items belong to.
 * @returns The array of saved items with their new IDs.
 */
export const saveFlyerItems = async (items: Omit<FlyerItem, 'id' | 'created_at' | 'flyer_id'>[], flyerId: number): Promise<FlyerItem[]> => {
    const supabaseClient = ensureSupabase();
    if (items.length === 0) return [];

    // Define the type for the items we are inserting, which matches the DB schema.
    type FlyerItemInsert = Database['public']['Tables']['flyer_items']['Insert'];

    const itemsToInsert: FlyerItemInsert[] = items.map(item => {
        // Create a new object without the properties that don't exist in the DB table
        return { ...item, flyer_id: flyerId, unit_price: item.unit_price as unknown as Json | null };
    });

    const { data: savedItems, error } = await supabaseClient
        .from('flyer_items')
        // The `itemsToInsert` array is now correctly typed for the insert operation.
        .insert(itemsToInsert)
        .select();
    if (error) throw new Error(`Failed to save flyer items: ${error.message}`);
    if (!savedItems) return [];

    // Safely map the returned data to the application type, handling unit_price
    return savedItems.map(item => ({
        ...item,
        unit_price: isUnitPrice(item.unit_price) ? item.unit_price : null,
    }));
};

/**
 * Retrieves all flyers from the database, ordered by most recent.
 * @returns An array of flyer objects.
 */
export const getFlyers = async (): Promise<Flyer[]> => {
    const supabaseClient = ensureSupabase();
    const data = await handleResponse<Flyer[]>(supabaseClient
        .from('flyers')
        .select('*, store:stores(*)')
        .order('created_at', { ascending: false }));
    return data ?? [];
};

/**
 * Retrieves all items for a specific flyer.
 * @param flyerId The ID of the flyer.
 * @returns An array of flyer item objects.
 */
export const getFlyerItems = async (flyerId: number): Promise<FlyerItem[]> => {
    const supabaseClient = ensureSupabase();

    // Fetch the data using the raw, auto-generated type from Supabase.
    // This avoids the initial type conflict with `unit_price`.
    const rawData = await handleResponse<Database['public']['Tables']['flyer_items']['Row'][]>(supabaseClient
        .from('flyer_items')
        .select('*')
        .eq('flyer_id', flyerId)
        .order('item', { ascending: true }));

    if (!rawData) {
        return [];
    }

    // Explicitly map the raw data to our application's `FlyerItem` type.
    // We use the `isUnitPrice` type guard to safely handle the conversion
    // from the generic `Json` type to our specific `UnitPrice` type.
    return rawData.map(item => ({
        ...item,
        // The type guard validates the shape at runtime. If it's not a valid
        // UnitPrice, we treat it as null to maintain type safety.
        unit_price: isUnitPrice(item.unit_price) ? item.unit_price : null,
    }));
};

/**
 * Looks for an existing flyer with a matching checksum to prevent duplicates.
 * @param checksum The SHA-256 checksum of the file.
 * @returns The found flyer object or null.
 */
export const findFlyerByChecksum = async (checksum: string): Promise<Flyer | null> => {
    const supabaseClient = ensureSupabase();

    const { data, error } = await supabaseClient
        .from('flyers')
        .select('*')
        .eq('checksum', checksum)
        .single();
    
    if (error && error.code !== 'PGRST116') throw new Error(`Error finding flyer by checksum: ${error.message}`);

    return data;
};

/**
 * Uploads a store logo and updates the store record.
 * This is designed to be a non-critical step. It won't throw an error but will log warnings.
 * It will only update the store if no logo_url is currently set.
 * @param storeId The ID of the store to update.
 * @param logoBase64 The base64 encoded logo string.
 * @returns The public URL of the logo if successful, otherwise null.
 */
export const uploadLogoAndUpdateStore = async (storeId: number, logoBase64: string): Promise<string | null> => {
    const supabaseClient = ensureSupabase();

    try {
        // Helper function to convert base64 to a Blob for uploading.
        const base64ToBlob = (base64: string, mimeType: string): Blob => {
            const byteCharacters = atob(base64);
            const byteNumbers = new Array(byteCharacters.length);
            for (let i = 0; i < byteCharacters.length; i++) {
                byteNumbers[i] = byteCharacters.charCodeAt(i);
            }
            const byteArray = new Uint8Array(byteNumbers);
            return new Blob([byteArray], { type: mimeType });
        };

        const logoBlob = base64ToBlob(logoBase64, 'image/png');
        const filePath = `logos/store_logo_${storeId}.png`;

        const { data, error: uploadError } = await supabaseClient.storage
            .from('flyers')
            .upload(filePath, logoBlob, {
                cacheControl: '3600',
                upsert: true, // Overwrite if it exists, simplifies logic
            });

        if (uploadError) {
            console.warn(`Failed to upload logo image: ${uploadError.message}`);
            return null;
        }

        const { data: urlData } = supabaseClient.storage.from('flyers').getPublicUrl(data.path);
        const publicUrl = urlData?.publicUrl;
        if (!publicUrl) {
            console.warn("Could not get public URL for uploaded logo.");
            return null;
        }

        // Update the store record with the new URL, but only if it's currently null.
        const { error: updateError } = await supabaseClient
            .from('stores')
            .update({ logo_url: publicUrl })
            .eq('id', storeId)
            .is('logo_url', null);

        if (updateError) {
            console.warn(`Failed to update store with new logo URL: ${updateError.message}`);
        }

        return publicUrl;
    } catch (e) { // This catch block is now valid because of the preceding `try`.
        const errorMessage = e instanceof Error ? e.message : String(e);
        console.warn(`An error occurred during logo processing: ${errorMessage}`);
        return null;
    }
};

/**
 * Retrieves all items a specific user is watching.
 * @param userId The UUID of the user.
 * @returns An array of master grocery item objects.
 */
export const getWatchedItems = async (userId: string): Promise<MasterGroceryItem[]> => {
    const supabaseClient = ensureSupabase();
    const data = await handleResponse<{ master_item: MasterGroceryItem & { category: { name: string } | null } }[] | null>(supabaseClient
        .from('user_watched_items')
        .select(`
            master_item:master_grocery_items (
                *,
                category:categories (name)
            )
        `)
        .eq('user_id', userId)
        .order('name', { referencedTable: 'master_grocery_items', ascending: true }));
    
    return (data?.map(item => ({ ...item.master_item, category_name: item.master_item.category?.name })) ?? []) as MasterGroceryItem[];
};

/**
 * Retrieves all master grocery items. This is used for matching during extraction.
 * @returns An array of master grocery item objects.
 */
export const getAllMasterItems = async (): Promise<MasterGroceryItem[]> => {
    const supabaseClient = ensureSupabase();

    // Define the expected raw type from the query, including the nested category object.
    type MasterItemWithCategory = Database['public']['Tables']['master_grocery_items']['Row'] & {
        category_name: { name: string } | null;
    };

    // Fetch the data using the raw, auto-generated type from Supabase.
    const rawData = await handleResponse<MasterItemWithCategory[]>(supabaseClient
        .from('master_grocery_items')
        .select('*, category_name:categories(name)')
        .order('name', { ascending: true }));

    // Explicitly map the raw data to our application's `MasterGroceryItem` type,
    // flattening the nested category name in the process.
    return (rawData?.map(item => ({
        ...item,
        category_name: item.category_name?.name,
    })) ?? []) as MasterGroceryItem[]; // The final cast is safe as we've constructed the correct shape.
};

/**
 * Adds a new item to a user's watchlist.
 * It first ensures the master item exists, then creates the user-item link.
 * @param userId The UUID of the user.
 * @param itemName The name of the item to add.
 * @param category The category of the item.
 * @returns The master item object that was added to the watchlist.
 */
export const addWatchedItem = async (userId: string, itemName: string, category: string): Promise<MasterGroceryItem> => {
    const supabaseClient = ensureSupabase();
    
    try {
        // 1. Find or create the category
        let categoryData = await handleResponse<{ id: number } | null>(
            supabaseClient
                .from('categories')
                .select('id')
                .eq('name', category)
                .maybeSingle()
        );

        if (!categoryData) {
            categoryData = await handleResponse<{ id: number } | null>(
                supabaseClient
                    .from('categories')
                    .insert({ name: category })
                    .select('id')
                    .single()
            );
        }

        // 2. Upsert the master item to ensure it exists and get its ID
        const { data: masterItem, error: masterItemError } = await supabaseClient
            .from('master_grocery_items')
            .upsert({ name: itemName.trim(), category_id: categoryData.id }, { onConflict: 'name' })
            .select('*, category_name:categories(name)')
            .single();
        if (masterItemError) throw new Error(`Failed to upsert master item: ${masterItemError.message}`);
        if (!masterItem) throw new Error("Master item operation did not return data.");

        // 3. Create the link in user_watched_items
        const { error: watchLinkError } = await supabaseClient
            .from('user_watched_items')
            .insert({ user_id: userId, master_item_id: masterItem.id });

        // Ignore duplicate errors (user already watching), throw others
        if (watchLinkError && watchLinkError.code !== '23505') { // 23505 is unique_violation
            throw new Error(`Failed to add item to watchlist: ${watchLinkError.message}`);
        } else if (watchLinkError) { // This block is now valid because of the preceding `if`.
            // Log the ignored duplicate error for debugging purposes if needed.
            logger.debug(`Ignored duplicate watch item error for user ${userId} and item ${masterItem.id}`);
        }
        // 4. Return the full master item object for UI update.
        // We explicitly construct the object to match the `MasterGroceryItem` type
        // by flattening the nested `category_name` object into a string.
        return {
            id: masterItem.id,
            created_at: masterItem.created_at,
            name: masterItem.name,
            category_id: masterItem.category_id,
            category_name: masterItem.category_name?.name ?? null,
        };
    } catch (error) {
        // This catch block is now valid because of the preceding `try`.
        const errorMessage = error instanceof Error ? error.message : 'An unknown error occurred in addWatchedItem.';
        throw new Error(`Failed to add watched item: ${errorMessage}`);
    }
};

/**
 * Removes an item from a user's watchlist.
 * @param userId The UUID of the user.
 * @param masterItemId The ID of the master item to remove.
 */
export const removeWatchedItem = async (userId: string, masterItemId: number): Promise<void> => {
    const supabaseClient = ensureSupabase();
    
    const { error } = await supabaseClient
        .from('user_watched_items')
        .delete()
        .eq('user_id', userId)
        .eq('master_item_id', masterItemId);

    if (error) {
        throw new Error(`Failed to remove watched item: ${error.message}`);
    }
};

/**
 * Fetches all flyer items for a given list of flyer IDs.
 * @param flyerIds An array of flyer IDs.
 * @returns An array of flyer item objects.
 */
export const getFlyerItemsForFlyers = async (flyerIds: number[]): Promise<FlyerItem[]> => {
    const supabaseClient = ensureSupabase();
    if (flyerIds.length === 0) return [];

    // Fetch the data using the raw, auto-generated type from Supabase.
    const rawData = await handleResponse<Database['public']['Tables']['flyer_items']['Row'][]>(supabaseClient
        .from('flyer_items')
        .select('*')
        .in('flyer_id', flyerIds));

    if (!rawData) {
        return [];
    }

    // Explicitly map the raw data to our application's `FlyerItem` type,
    // using the type guard to safely handle the `unit_price` conversion.
    return rawData.map(item => ({
        ...item,
        unit_price: isUnitPrice(item.unit_price) ? item.unit_price : null,
    }));
};

/**
 * Counts the total number of items across a list of flyers.
 * @param flyerIds An array of flyer IDs.
 * @returns The total count of items.
 */
export const countFlyerItemsForFlyers = async (flyerIds: number[]): Promise<number> => {
    const supabaseClient = ensureSupabase();
    if (flyerIds.length === 0) return 0;
    
    const { count, error } = await supabaseClient
        .from('flyer_items')
        .select('*', { count: 'exact', head: true })
        .in('flyer_id', flyerIds);
    if (error) throw new Error(`Error counting items for flyers: ${error.message}`);
    
    return count || 0;
};

/**
 * Fetches all flyer items corresponding to a user's watched items to build a price history.
 * @param watchedItems An array of master grocery items.
 * @returns An array of historical price data points.
 */
export const getHistoricalWatchedItems = async (watchedItems: MasterGroceryItem[]): Promise<Pick<FlyerItem, 'master_item_id' | 'price_in_cents' | 'created_at'>[]> => {
    const supabaseClient = ensureSupabase();
    if (watchedItems.length === 0) return [];
    
    const watchedItemIds = watchedItems.map(item => item.id);
    
    const data = await handleResponse<Pick<FlyerItem, 'master_item_id' | 'price_in_cents' | 'created_at'>[] | null>(supabaseClient
        .from('flyer_items')
        .select('master_item_id, price_in_cents, created_at')
        .in('master_item_id', watchedItemIds)
        .not('price_in_cents', 'is', null)
        .order('created_at', { ascending: true }));
    
    return data ?? [];
};

/**
 * Fetches a user's profile from the database.
 * @param userId The UUID of the user.
 * @returns The user's profile object.
 */
export const getUserProfile = async (userId: string): Promise<Profile | null> => {
    const supabaseClient = ensureSupabase();

    const data = await handleResponse<Profile | null>(supabaseClient
        .from('profiles')
        .select('*, role')
        .eq('id', userId)
        .single());

    if (!data) { // handleResponse returns null if no data
        console.error("Error fetching user profile: No data returned.");
        return null;
    }
    // Cast the result back to the expected application type
    return data as Profile | null;
};

/**
 * Updates a user's profile information.
 * @param userId The UUID of the user.
 * @param updates The profile fields to update.
 * @returns The updated profile object.
 */
export const updateUserProfile = async (userId: string, updates: { full_name?: string; avatar_url?: string }): Promise<Profile> => {
    const supabaseClient = ensureSupabase();
    const data = await handleResponse<Profile | null>(supabaseClient
        .from('profiles')
        // Cast to `any` to handle potential JSONB type mismatches if more fields are added
        .update(updates)
        .eq('id', userId)
        .select()
        .single());
    return data as Profile; // Cast to application's Profile type
};

/**
 * Updates a user's preferences.
 * @param userId The UUID of the user.
 * @param preferences The preferences object to save.
 * @returns The updated profile object.
 */
export const updateUserPreferences = async (userId: string, preferences: Profile['preferences']): Promise<Profile> => {
    const supabaseClient = ensureSupabase();

    const data = await handleResponse<Profile | null>(supabaseClient
        .from('profiles')
        // Cast to `any` to handle the JSONB type mismatch for `preferences`
        .update({ preferences: preferences as Json })
        .eq('id', userId)
        .select().single()
    );
    return data as Profile; // Cast is safe here because we expect a single result
};

/**
 * Updates the authenticated user's password.
 * @param newPassword The new password.
 */
export const updateUserPassword = async (newPassword: string): Promise<void> => {
    const supabaseClient = ensureSupabase();

    const { error } = await supabaseClient.auth.updateUser({ password: newPassword });
    if (error) throw new Error(`Error updating password: ${error.message}`);
};

/**
 * Gathers all data for a specific user for export.
 * @param userId The UUID of the user.
 * @returns An object containing all of the user's data.
 */

type WatchedItemExport = { created_at: string; item: { name: string; category: { name: string } | null } | null };
type ShoppingListExport = { name: string; created_at: string; items: { custom_item_name: string | null; quantity: number; is_purchased: boolean; master_item: { name: string } | null }[] };

interface UserDataExport {
    profile: Profile | null;
    watchedItems: WatchedItemExport[] | null;
    shoppingLists: ShoppingListExport[] | null;
}

export const exportUserData = async (userId: string): Promise<UserDataExport> => {
    const supabaseClient = ensureSupabase();

    const profile = await handleResponse<Profile | null>(supabaseClient
        .from('profiles')
        .select('*')
        .eq('id', userId)
        .single());

    const watchedItems = await handleResponse<WatchedItemExport[] | null>(supabaseClient
        .from('user_watched_items')
        .select('created_at, item:master_grocery_items(name, category:categories(name))')
        .eq('user_id', userId));

    const shoppingLists = await handleResponse<ShoppingListExport[] | null>(supabaseClient
        .from('shopping_lists')
        .select('name, created_at, items:shopping_list_items(custom_item_name, quantity, is_purchased, master_item:master_grocery_items(name))')
        .eq('user_id', userId));

    return {
        profile,
        watchedItems,
        shoppingLists,
    };
};


/**
 * Deletes the current user's account by invoking a secure Edge Function.
 * @param password The user's current password for verification.
 */
export const deleteUserAccount = async (password: string): Promise<void> => {
    // Adding detailed logging to trace who is calling this function.
    console.trace("deleteUserAccount called. This trace will show the call stack.");
    const supabaseClient = ensureSupabase();

    // Invoking the 'delete-user' edge function.
    const { data, error } = await supabaseClient.functions.invoke('delete-user', {
        body: { password },
    });

    if (error) {
        let errorDetails = `Edge Function returned an error: ${error.message}.`;
        if (error.context) {
            try {
                const errorBody = await error.context.json();
                const message = errorBody.error || 'No error message in body.';
                const stack = errorBody.stack || 'No stack trace in body.';
                errorDetails = `Error: ${message}\n\nStack Trace:\n${stack}`;
            } catch {
                 errorDetails += `\nCould not parse error response body.`;
            }
        }
        throw new Error(errorDetails);
    }
    if (data?.error) throw new Error(data.error);
};

/**
 * Calls the `system-check` Edge Function to verify the backend setup.
 * @returns The results of the system checks.
 */
export const invokeSystemCheckFunction = async (): Promise<unknown> => {
    const supabaseClient = ensureSupabase();

    const { data, error } = await supabaseClient.functions.invoke('system-check');
    
    if (error) {
        let errorDetails = `System check function failed: ${error.message}.`;
        if (error.message.includes("Not found")) {
            errorDetails = "The 'system-check' Edge Function is not deployed. Please follow the instructions in the README to deploy it.";
        } else if (error.context) {
            try {
                const errorBody = await error.context.json();
                errorDetails += `\nDetails: ${errorBody.error || 'Unknown error'}`;
            } catch { /* ignore parsing error */ } 
        }
        throw new Error(errorDetails);
    }
    if (data?.error) throw new Error(data.error);
    return data.results;
};


/**
 * Creates the initial development users by invoking a secure Edge Function.
 */
export const invokeSeedDatabaseFunction = async (): Promise<{ message: string; }> => {
    const supabaseClient = ensureSupabase();

    const { data, error } = await supabaseClient.functions.invoke('seed-database');
    
    if (error) {
        let errorDetails = `Edge Function returned a non-2xx status code: ${error.message}.`;
        if (error.context) {
            try {
                const errorBody = await error.context.json();
                const message = errorBody.error || 'No error message in body.';
                const stack = errorBody.stack || 'No stack trace in body.';
                errorDetails = `Error: ${message}\n\nStack Trace:\n${stack}`;
            } catch {
                errorDetails += `\nCould not parse error response body. Raw response might be in browser network tab.`;
            }
        }
        throw new Error(errorDetails);
    }
    
    if (data?.error) throw new Error(data.error);
    return data;
};

/**
 * Fetches all pending suggested corrections from the database.
 * This is an admin-only function.
 * @returns An array of suggested correction objects with related user and item data.
 */
export const getSuggestedCorrections = async (): Promise<SuggestedCorrection[]> => {
    const supabaseClient = ensureSupabase();

    // Define a more specific type for the query result to avoid `any`.
    type CorrectionWithRelations = SuggestedCorrection & {
        user: { email: string | null } | null;
        item: { item: string; price_display: string } | null;
    };

    // Re-writing this query explicitly to avoid a complex type-inference issue
    // that was causing the TypeScript language server to report a phantom syntax error.
    const query = supabaseClient
        .from('suggested_corrections')
        .select(`
            *,
            user:profiles(email),
            item:flyer_items(item, price_display)
        `)
        .eq('status', 'pending')
        .order('created_at', { ascending: true });

    const { data, error } = await query;

    if (error) {
        throw new Error(`Failed to get suggested corrections: ${error.message}`);
    }

    // The data can be null if the query returns no rows, so we handle that case.
    if (!data) {
        return [];
    }

    return (data as unknown as CorrectionWithRelations[]).map((c) => ({
        ...c,
        user_email: c.user?.email ?? 'Unknown',
        flyer_item_name: c.item?.item ?? 'Unknown Item',
        flyer_item_price_display: c.item?.price_display ?? 'N/A'
    })) as SuggestedCorrection[];
};

/**
 * Approves a suggested correction by calling the `approve_correction` RPC.
 * This is an admin-only function.
 * @param correctionId The ID of the correction to approve.
 */
export const approveCorrection = async (correctionId: number): Promise<void> => {
    const supabaseClient = ensureSupabase();

    const { error } = await supabaseClient.rpc('approve_correction', { p_correction_id: correctionId });

    if (error) {
        throw new Error(`Failed to approve correction: ${error.message}`);
    }
};

/**
 * Rejects a suggested correction.
 * This is an admin-only function.
 * @param correctionId The ID of the correction to reject.
 */
export const rejectCorrection = async (correctionId: number): Promise<void> => {
    const supabaseClient = ensureSupabase();

    const { error } = await supabaseClient.from('suggested_corrections').update({ status: 'rejected', reviewed_at: new Date().toISOString() }).eq('id', correctionId);

    if (error) throw new Error(`Failed to reject correction: ${error.message}`);
};


// =============================================
// SHOPPING LIST FUNCTIONS
// =============================================

/**
 * Fetches all shopping lists for a user, including their items.
 * @param userId The UUID of the user.
 * @returns An array of shopping list objects.
 */
export const getShoppingLists = async (userId: string): Promise<ShoppingList[]> => {
    const supabaseClient = ensureSupabase();    
    const data = await handleResponse<ShoppingList[] | null>(
      supabaseClient
        .from('shopping_lists')
        .select(`
            *,
            items:shopping_list_items (
                *,
                master_item:master_grocery_items (name)
            )
        `)
        .eq('user_id', userId)
        .order('created_at', { ascending: true })
        .order('added_at', { ascending: true, referencedTable: 'shopping_list_items' })
    );
    return data ?? [];
};

/**
 * Creates a new shopping list for a user.
 * @param userId The UUID of the user.
 * @param name The name of the new list.
 * @returns The newly created shopping list object.
 */
export const createShoppingList = async (userId: string, name: string): Promise<ShoppingList> => {
    const supabaseClient = ensureSupabase();
    const data = await handleResponse<ShoppingList | null>(supabaseClient
        .from('shopping_lists')
        .insert({ user_id: userId, name })
        .select()
        .single());
    return { ...data, items: [] }; // Return with empty items array
};

/**
 * Deletes a shopping list.
 * @param listId The ID of the list to delete.
 */
export const deleteShoppingList = async (listId: number): Promise<void> => {
    const supabaseClient = ensureSupabase();

    const { error } = await supabaseClient
        .from('shopping_lists')
        .delete()
        .eq('id', listId);
    if (error) throw new Error(`Error deleting shopping list: ${error.message}`);
};

/**
 * Adds an item to a shopping list.
 * @param listId The ID of the list.
 * @param masterItemId Optional ID of the master grocery item.
 * @param customItemName Optional name for a custom item.
 * @returns The newly created shopping list item.
 */
export const addShoppingListItem = async (listId: number, { masterItemId, customItemName }: { masterItemId?: number; customItemName?: string }): Promise<ShoppingListItem> => {
	const supabaseClient = ensureSupabase();
	if (!masterItemId && !customItemName) {
		throw new Error("Either masterItemId or customItemName must be provided.");
	}

	let query;

	if (masterItemId) {
		const itemToUpsert = {
			shopping_list_id: listId,
			master_item_id: masterItemId,
			custom_item_name: null, // Ensure the object shape is complete for the type checker
			quantity: 1,
		};
		query = supabaseClient.from('shopping_list_items').upsert(itemToUpsert, { onConflict: 'shopping_list_id, master_item_id' });
	} else {
		const itemToInsert = {
			shopping_list_id: listId,
			master_item_id: null, // Ensure the object shape is complete
			custom_item_name: customItemName,
			quantity: 1,
		};
		query = supabaseClient.from('shopping_list_items').insert(itemToInsert);
	}

	// Bypassing the generic `handleResponse` helper to resolve the complex type inference issue.
	const { data, error } = await query.select('*, master_item:master_grocery_items(name)').single();

	if (error) throw new Error(`Failed to add shopping list item: ${error.message}`);
	if (!data) throw new Error("Adding shopping list item did not return data.");

	return data as ShoppingListItem;
};

/**
 * Updates a shopping list item.
 * @param itemId The ID of the item to update.
 * @param updates The fields to update (e.g., is_purchased, quantity).
 * @returns The updated shopping list item.
 */
export const updateShoppingListItem = async (itemId: number, updates: Partial<Omit<ShoppingListItem, 'id' | 'master_item'>>): Promise<ShoppingListItem> => {
    const supabaseClient = ensureSupabase();
    // The 'id' and 'master_item' cannot be part of the update payload.
    const { ...updateData } = updates;

    const data = await handleResponse<ShoppingListItem>(supabaseClient
        .from('shopping_list_items')
        .update(updateData)
        .eq('id', itemId)
        .select('*, master_item:master_grocery_items(name)')
        .single());
    return data as ShoppingListItem;
};

/**
 * Removes an item from a shopping list.
 * @param itemId The ID of the item to remove.
 */
export const removeShoppingListItem = async (itemId: number): Promise<void> => {
    const supabaseClient = ensureSupabase();

    const { error } = await supabaseClient
        .from('shopping_list_items')
        .delete()
        .eq('id', itemId);
    if (error) throw new Error(`Error removing shopping list item: ${error.message}`);
};