Report the average price of each item

Author: at1as

README.md

@@ -0,0 +1,43 @@
+# Price Tracker
+
+Simple script to fetch current price of items on Amazon and archive historical prices
+
+
+### Usage
+
+Edit `items.json` with a key value list of the item name and it's URL on Amazon
+
+```
+$ go run main.go
+```
+
+
+### Output
+
+```
+atlas$ go run main.go
+2017/10/22 14:24:29 Fetching today's prices...
+
+2017/10/22 14:24:32 Today's price for "Seagate 8 TB Hard Drive" is $169.99
+
+2017/10/22 14:24:32 The Average price for this item was $169.99 over 2 samples
+2017/10/22 14:24:32 The max price for this item was $169.99 on 2017-10-21
+2017/10/22 14:24:32 The min price for this item was $169.99 on 2017-10-21
+
+2017/10/22 14:24:34 Today's price for "Western Digital 8 TB Hard Drive" is $198.99
+
+2017/10/22 14:24:34 The Average price for this item was $198.99 over 2 samples
+2017/10/22 14:24:34 The max price for this item was $198.99 on 2017-10-21
+2017/10/22 14:24:34 The min price for this item was $198.99 on 2017-10-21
+```
+
+
+### TODO
+
+* Provide range over which average price samples span
+* tests
+
+
+### Notes
+
+* Build with go1.6.2 on macOS 10.11

items.json

@@ -0,0 +1,32 @@
+{
+	"Items": [
+		{
+			"Name": "Seagate 8 TB Hard Drive",
+			"Link": "https://www.amazon.com/Seagate-Expansion-Desktop-External-STEB8000100/dp/B01HAPGEIE",
+			"Prices": [
+				{
+					"Date": "2017-10-21",
+					"Price": "$169.99"
+				},
+				{
+					"Date": "2017-10-22",
+					"Price": "$169.99"
+				}
+			]
+		},
+		{
+			"Name": "Western Digital 8 TB Hard Drive",
+			"Link": "https://www.amazon.com/dp/B01LQQHLGC/ref=twister_B0751SCZW7",
+			"Prices": [
+				{
+					"Date": "2017-10-21",
+					"Price": "$198.99"
+				},
+				{
+					"Date": "2017-10-22",
+					"Price": "$198.99"
+				}
+			]
+		}
+	]
+}

main.go

@@ -34,19 +34,28 @@ type Config struct {
 
 func main() {
 
-  log.Printf("Fetching today's prices...\n\n")
+  log.Printf("Fetching today's prices...")
 
   json_file := "items.json"
   product_link_map := getProductList(json_file)
 
   for name, link := range product_link_map {
     price := getPriceFromSite(name, link)
+    
+    fmt.Println("")
     log.Printf(`Today's price for "%s" is %s`, name, price)
+    fmt.Println("")
 
     addPriceToProductList(name, price, json_file)
 
     average_price, sample_size := getAveragePriceForItem(name, json_file)
-    log.Printf("The Average price for this item was $%.2f over %d samples\n\n", average_price, sample_size)
+    log.Printf("The Average price for this item was $%.2f over %d samples", average_price, sample_size)
+
+    min_price, max_price, valid := getMinMaxPriceForItem(name, json_file)
+    if valid {
+      log.Printf("The max price for this item was %s on %s", max_price.Price, max_price.Date)
+      log.Printf("The min price for this item was %s on %s", min_price.Price, min_price.Date)
+    }
   }
 }
 
@@ -172,6 +181,48 @@ func getAveragePriceForItem(name string, filename string) (float32, int) {
 }
 
 
+func getMinMaxPriceForItem(name string, filename string) (Price, Price, bool) {
+  
+  raw, err := ioutil.ReadFile(filename)
+
+  if err != nil {
+    panic("Failed to read JSON file : " + filename + " => " + err.Error())
+  }
+  
+  var conf Config
+  json.Unmarshal(raw, &conf)
+  
+  valid := false
+  samples := 0
+  var min_price Price
+  var max_price Price
+
+  for item := range conf.Items {
+    if conf.Items[item].Name == name {
+      for i := range conf.Items[item].Prices {
+        
+        current_price := conf.Items[item].Prices[i]
+
+        if current_price.Price > max_price.Price {
+          max_price = current_price
+        }
+
+        if current_price.Price < min_price.Price || i == 0 {
+          min_price = current_price
+        }
+
+        samples += 1
+      }
+    }
+  }
+
+  if samples > 0 { 
+    valid = true
+  }
+
+  return min_price, max_price, valid
+}
+
 
 func toJson(j Config) string {
   bytes, err := json.MarshalIndent(j, "", "\t")