package

2025-11-10 20:38:51 +01:00
commit 19d7ad0de6
6 changed files with 385 additions and 0 deletions
--- a/pkg/inventory/redis_service.go
+++ b/pkg/inventory/redis_service.go
@@ -0,0 +1,249 @@
+package inventory
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"strconv"
+
+	"github.com/redis/go-redis/v9"
+)
+
+type RedisInventoryService struct {
+	client     *redis.Client
+	ctx        context.Context
+	luaScripts map[string]*redis.Script
+}
+
+func NewRedisInventoryService(client *redis.Client, ctx context.Context) (*RedisInventoryService, error) {
+	rdb := client
+
+	// Ping Redis to check connection
+	_, err := rdb.Ping(ctx).Result()
+	if err != nil {
+		return nil, err
+	}
+
+	return &RedisInventoryService{
+		client:     rdb,
+		ctx:        ctx,
+		luaScripts: make(map[string]*redis.Script),
+	}, nil
+}
+
+func (s *RedisInventoryService) LoadLuaScript(key string) error {
+	// Get the script from Redis
+	script, err := s.client.Get(s.ctx, key).Result()
+	if err != nil {
+		return err
+	}
+
+	// Load the script into the luaScripts cache
+	s.luaScripts[key] = redis.NewScript(script)
+	return nil
+}
+
+func (s *RedisInventoryService) AddWarehouse(warehouse *Warehouse) error {
+	// Convert warehouse to Redis-friendly format
+	data := map[string]interface{}{
+		"id":        string(warehouse.ID),
+		"name":      warehouse.Name,
+		"inventory": warehouse.Inventory,
+	}
+
+	// Store in Redis with a key pattern like "warehouse:<ID>"
+	key := "warehouse:" + string(warehouse.ID)
+	_, err := s.client.HMSet(s.ctx, key, data).Result()
+	return err
+}
+
+func (s *RedisInventoryService) GetInventory(sku SKU, locationID LocationID) (int64, error) {
+
+	cmd := s.client.Get(s.ctx, getInventoryKey(sku, locationID))
+	if err := cmd.Err(); err != nil {
+		return 0, err
+	}
+
+	i, err := cmd.Int64()
+	if err != nil {
+		return 0, err
+	}
+
+	return i, nil
+}
+
+func getInventoryKey(sku SKU, locationID LocationID) string {
+	return fmt.Sprintf("inventory:%s:%s", sku, locationID)
+}
+
+func (s *RedisInventoryService) UpdateInventory(rdb redis.Pipeliner, sku SKU, locationID LocationID, quantity int64) error {
+	key := getInventoryKey(sku, locationID)
+	cmd := rdb.Set(s.ctx, key, quantity, 0)
+	return cmd.Err()
+}
+
+var (
+	ErrInsufficientInventory = errors.New("insufficient inventory")
+	ErrInvalidQuantity       = errors.New("invalid quantity")
+	ErrMissingReservation    = errors.New("missing reservation")
+)
+
+func makeKeysAndArgs(req ...ReserveRequest) ([]string, []string) {
+	keys := make([]string, len(req))
+	args := make([]string, len(req))
+	for i, r := range req {
+		if r.Quantity <= 0 {
+			return nil, nil
+		}
+		keys[i] = getInventoryKey(r.SKU, r.LocationID)
+		args[i] = strconv.Itoa(int(r.Quantity))
+	}
+	return keys, args
+}
+
+func (s *RedisInventoryService) ReservationCheck(req ...ReserveRequest) (*ReserveRequest, error) {
+	if len(req) == 0 {
+		return nil, ErrMissingReservation
+	}
+
+	keys, args := makeKeysAndArgs(req...)
+	if keys == nil || args == nil {
+		return nil, ErrInvalidQuantity
+	}
+
+	cmd := reservationCheck.Run(s.ctx, s.client, keys, args)
+	if err := cmd.Err(); err != nil {
+		return nil, err
+	}
+	val := cmd.Val().(int64)
+	if val > 0 {
+		return nil, nil // success
+	}
+	// val is negative index of failing request
+	failingIndex := int(-val) - 1 // 0-based
+	return &req[failingIndex], ErrInsufficientInventory
+}
+
+func (s *RedisInventoryService) ReserveInventory(req ...ReserveRequest) error {
+	if len(req) == 0 {
+		return ErrMissingReservation
+	}
+
+	keys, args := makeKeysAndArgs(req...)
+	if keys == nil || args == nil {
+		return ErrInvalidQuantity
+	}
+	cmd := reserveScript.Run(s.ctx, s.client, keys, args)
+	if err := cmd.Err(); err != nil {
+		return err
+	}
+	if val, err := cmd.Int(); err != nil {
+		return err
+	} else if val != 1 {
+		return ErrInsufficientInventory
+	}
+	return nil
+}
+
+var reservationCheck = redis.NewScript(`
+-- Get the number of keys passed
+local num_keys = #KEYS
+
+-- Ensure the number of keys matches the number of quantities
+if num_keys ~= #ARGV then
+  return {err = "Script requires the same number of keys and quantities."}
+end
+
+-- ---
+-- CHECK PHASE
+-- ---
+-- Loop through all keys to check their values first
+for i = 1, num_keys do
+  local key = KEYS[i]
+  local quantity_to_check = tonumber(ARGV[i])
+
+  -- Fail if the quantity is not a valid number
+  if not quantity_to_check then
+    return {err = "Invalid quantity provided for key: " .. key}
+  end
+
+  -- Get the current value stored at the key
+  local current_val = tonumber(redis.call('GET', key))
+
+  -- Check the condition
+  -- Fail if:
+  -- 1. The key doesn't exist (current_val is nil)
+  -- 2. The value is not > the required quantity
+  if not current_val or current_val < quantity_to_check then
+    -- Return negative index (1-based) to indicate which request failed
+    return -i
+  end
+end
+
+return 1
+`)
+
+var reserveScript = redis.NewScript(`
+-- Get the number of keys passed
+local num_keys = #KEYS
+
+-- Ensure the number of keys matches the number of quantities
+if num_keys ~= #ARGV then
+  return {err = "Script requires the same number of keys and quantities."}
+end
+
+local new_values = {}
+local payload = {}
+
+-- ---
+-- 1. CHECK PHASE
+-- ---
+-- Loop through all keys to check their values first
+for i = 1, num_keys do
+  local key = KEYS[i]
+  local quantity_to_check = tonumber(ARGV[i])
+
+  -- Fail if the quantity is not a valid number
+  if not quantity_to_check then
+    return {err = "Invalid quantity provided for key: " .. key}
+  end
+
+  -- Get the current value stored at the key
+  local current_val = tonumber(redis.call('GET', key))
+
+  -- Check the condition
+  -- Fail if:
+  -- 1. The key doesn't exist (current_val is nil)
+  -- 2. The value is not > the required quantity
+  if not current_val or current_val < quantity_to_check then
+    -- Return 0 to indicate the operation failed and no changes were made
+    return 0
+  end
+
+  -- If the check passes, store the new value
+  local new_val = current_val - quantity_to_check
+  table.insert(new_values, new_val)
+
+  -- Add this key and its *new* value to our payload map
+  payload[key] = new_val
+end
+
+-- ---
+-- 2. UPDATE PHASE
+-- ---
+-- If the script reaches this point, all checks passed.
+-- Now, loop again and apply all the updates.
+for i = 1, num_keys do
+  local key = KEYS[i]
+  local new_val = new_values[i]
+
+  -- Set the key to its new calculated value
+  redis.call('SET', key, new_val)
+end
+local message_payload = cjson.encode(payload)
+
+-- Publish the JSON-encoded message to the specified channel
+redis.call('PUBLISH', "inventory_changed", message_payload)
+-- Return 1 to indicate the operation was successful
+return 1
+`)