feat: add initial database schema migration (#13)

- Create all core tables: inventory_items, products, tags, item_tags, units, user_profiles
- Add ENUM types: tag_category, unit_type
- Implement indexes for performance optimization
- Add helper functions: update_updated_at(), convert_unit(), search_products()
- Add triggers for automatic timestamp updates
- Full-text search support for products
- Comprehensive table comments for documentation

Closes #13

supabase/migrations/001_initial_schema.sql

@@ -0,0 +1,282 @@
+-- Migration: Initial database schema
+-- Created: 2026-02-09
+-- Issue: #13
+-- Description: Creates core tables for Pantry app (inventory, products, tags, units)
+
+-- ======================
+-- ENUM TYPES
+-- ======================
+
+CREATE TYPE tag_category AS ENUM (
+  'position',    -- Location: fridge, freezer, pantry
+  'type',        -- Food type: dairy, meat, vegan
+  'dietary',     -- Diet: gluten-free, vegan, organic
+  'custom'       -- User-defined
+);
+
+CREATE TYPE unit_type AS ENUM (
+  'weight',   -- kg, g, lb, oz
+  'volume',   -- L, mL, cup, tbsp
+  'count',    -- pcs, items (no conversion)
+  'custom'    -- can, jar, bottle (user-defined)
+);
+
+-- ======================
+-- BASE TABLES (no foreign keys)
+-- ======================
+
+-- Units: measurement units with conversion support
+CREATE TABLE units (
+  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  
+  -- Core data
+  name TEXT NOT NULL,           -- "kilogram", "liter", "piece"
+  abbreviation TEXT NOT NULL,   -- "kg", "L", "pcs"
+  unit_type unit_type NOT NULL,
+  
+  -- Conversion system
+  base_unit_id UUID REFERENCES units(id),  -- NULL = this is a base unit
+  conversion_factor DECIMAL(20,10),        -- Factor to convert to base unit
+  
+  -- Metadata
+  is_default BOOLEAN DEFAULT false,  -- Shipped with app
+  created_by UUID REFERENCES auth.users(id),  -- NULL = system unit
+  created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  
+  CONSTRAINT unique_unit_abbr UNIQUE (abbreviation, created_by),
+  CONSTRAINT check_conversion_logic CHECK (
+    (base_unit_id IS NULL AND conversion_factor IS NULL) OR 
+    (base_unit_id IS NOT NULL AND conversion_factor IS NOT NULL)
+  )
+);
+
+-- Tags: flexible labeling system
+CREATE TABLE tags (
+  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  
+  -- Core data
+  name TEXT NOT NULL,
+  category tag_category NOT NULL DEFAULT 'custom',
+  
+  -- Visual
+  icon TEXT,    -- Emoji or icon name: "🧊", "cheese"
+  color TEXT,   -- Hex color: "#3b82f6"
+  
+  -- Ownership
+  created_by UUID REFERENCES auth.users(id),  -- NULL = system tag
+  created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  
+  CONSTRAINT unique_tag_name UNIQUE (name, created_by)
+);
+
+-- ======================
+-- MAIN TABLES
+-- ======================
+
+-- Products: cached product data from Open Food Facts
+CREATE TABLE products (
+  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  
+  -- Open Food Facts data
+  barcode TEXT UNIQUE NOT NULL,
+  name TEXT NOT NULL,
+  brand TEXT,
+  image_url TEXT,
+  image_small_url TEXT,  -- Thumbnail
+  
+  -- Categories from Open Food Facts
+  categories TEXT[],  -- Array: ['dairy', 'milk']
+  
+  -- Nutrition (optional, for future features)
+  nutrition JSONB,  -- Full nutrition data
+  
+  -- Defaults
+  default_unit_id UUID REFERENCES units(id),
+  default_quantity DECIMAL(10,2),  -- E.g., 1L bottle
+  
+  -- Metadata
+  source TEXT DEFAULT 'openfoodfacts',
+  cached_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  last_fetched TIMESTAMPTZ,
+  
+  -- Quality score (from Open Food Facts)
+  completeness_score INTEGER CHECK (completeness_score BETWEEN 0 AND 100)
+);
+
+-- Inventory Items: actual items in your kitchen right now
+CREATE TABLE inventory_items (
+  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  
+  -- Product reference (nullable for custom items)
+  product_id UUID REFERENCES products(id) ON DELETE SET NULL,
+  
+  -- Core data
+  name TEXT NOT NULL,  -- Product name or custom name
+  quantity DECIMAL(10,2) NOT NULL CHECK (quantity >= 0),
+  unit_id UUID NOT NULL REFERENCES units(id),
+  
+  -- Optional metadata
+  expiry_date DATE,
+  location TEXT,  -- Free text: "top shelf", "door", etc.
+  notes TEXT,
+  
+  -- Audit trail
+  added_by UUID NOT NULL REFERENCES auth.users(id),
+  created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+-- Item Tags: many-to-many relationship between items and tags
+CREATE TABLE item_tags (
+  item_id UUID NOT NULL REFERENCES inventory_items(id) ON DELETE CASCADE,
+  tag_id UUID NOT NULL REFERENCES tags(id) ON DELETE CASCADE,
+  
+  created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  
+  PRIMARY KEY (item_id, tag_id)
+);
+
+-- User Profiles: additional user metadata
+CREATE TABLE user_profiles (
+  id UUID PRIMARY KEY REFERENCES auth.users(id) ON DELETE CASCADE,
+  
+  display_name TEXT,
+  avatar_url TEXT,
+  
+  -- Preferences
+  default_unit_system TEXT DEFAULT 'metric',  -- 'metric' or 'imperial'
+  theme TEXT DEFAULT 'auto',                  -- 'light', 'dark', 'auto'
+  
+  created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+-- ======================
+-- INDEXES
+-- ======================
+
+-- Units
+CREATE INDEX idx_units_type ON units(unit_type);
+CREATE INDEX idx_units_base ON units(base_unit_id);
+
+-- Tags
+CREATE INDEX idx_tags_category ON tags(category);
+CREATE INDEX idx_tags_created_by ON tags(created_by);
+
+-- Products
+CREATE UNIQUE INDEX idx_products_barcode ON products(barcode);
+CREATE INDEX idx_products_name ON products USING GIN (to_tsvector('english', name));
+CREATE INDEX idx_products_search ON products 
+  USING GIN (to_tsvector('english', name || ' ' || COALESCE(brand, '')));
+
+-- Inventory Items
+CREATE INDEX idx_items_product ON inventory_items(product_id);
+CREATE INDEX idx_items_added_by ON inventory_items(added_by);
+CREATE INDEX idx_items_expiry ON inventory_items(expiry_date) WHERE expiry_date IS NOT NULL;
+
+-- Item Tags
+CREATE INDEX idx_item_tags_tag ON item_tags(tag_id);
+CREATE INDEX idx_item_tags_item ON item_tags(item_id);
+
+-- ======================
+-- FUNCTIONS
+-- ======================
+
+-- Auto-update timestamp trigger function
+CREATE OR REPLACE FUNCTION update_updated_at()
+RETURNS TRIGGER AS $$
+BEGIN
+  NEW.updated_at = NOW();
+  RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;
+
+-- Unit conversion function
+CREATE OR REPLACE FUNCTION convert_unit(
+  quantity DECIMAL,
+  from_unit_id UUID,
+  to_unit_id UUID
+)
+RETURNS DECIMAL AS $$
+DECLARE
+  from_factor DECIMAL;
+  to_factor DECIMAL;
+  from_type unit_type;
+  to_type unit_type;
+  base_quantity DECIMAL;
+BEGIN
+  -- Get unit types and conversion factors
+  SELECT unit_type, 
+         COALESCE(conversion_factor, 1.0) INTO from_type, from_factor
+  FROM units WHERE id = from_unit_id;
+  
+  SELECT unit_type,
+         COALESCE(conversion_factor, 1.0) INTO to_type, to_factor
+  FROM units WHERE id = to_unit_id;
+  
+  -- Check if units are compatible
+  IF from_type != to_type THEN
+    RAISE EXCEPTION 'Cannot convert between % and %', from_type, to_type;
+  END IF;
+  
+  -- Convert to base unit, then to target unit
+  base_quantity := quantity * from_factor;
+  RETURN base_quantity / to_factor;
+END;
+$$ LANGUAGE plpgsql IMMUTABLE;
+
+-- Full-text search function for products
+CREATE OR REPLACE FUNCTION search_products(search_query TEXT)
+RETURNS TABLE (
+  id UUID,
+  barcode TEXT,
+  name TEXT,
+  brand TEXT,
+  rank REAL
+) AS $$
+BEGIN
+  RETURN QUERY
+  SELECT 
+    p.id,
+    p.barcode,
+    p.name,
+    p.brand,
+    ts_rank(to_tsvector('english', p.name || ' ' || COALESCE(p.brand, '')), 
+            plainto_tsquery('english', search_query)) AS rank
+  FROM products p
+  WHERE to_tsvector('english', p.name || ' ' || COALESCE(p.brand, '')) 
+        @@ plainto_tsquery('english', search_query)
+  ORDER BY rank DESC
+  LIMIT 20;
+END;
+$$ LANGUAGE plpgsql;
+
+-- ======================
+-- TRIGGERS
+-- ======================
+
+-- Auto-update timestamp triggers
+CREATE TRIGGER update_items_updated_at
+  BEFORE UPDATE ON inventory_items
+  FOR EACH ROW
+  EXECUTE FUNCTION update_updated_at();
+
+CREATE TRIGGER update_profiles_updated_at
+  BEFORE UPDATE ON user_profiles
+  FOR EACH ROW
+  EXECUTE FUNCTION update_updated_at();
+
+-- ======================
+-- COMMENTS
+-- ======================
+
+COMMENT ON TABLE inventory_items IS 'Current inventory items in the kitchen';
+COMMENT ON TABLE products IS 'Cached product data from Open Food Facts';
+COMMENT ON TABLE tags IS 'Flexible labeling system for organization';
+COMMENT ON TABLE item_tags IS 'Many-to-many relationship between items and tags';
+COMMENT ON TABLE units IS 'Measurement units with conversion support';
+COMMENT ON TABLE user_profiles IS 'Additional user metadata and preferences';
+
+COMMENT ON FUNCTION update_updated_at() IS 'Automatically updates the updated_at timestamp';
+COMMENT ON FUNCTION convert_unit(DECIMAL, UUID, UUID) IS 'Converts quantity between compatible units';
+COMMENT ON FUNCTION search_products(TEXT) IS 'Full-text search for products by name and brand';