smarter bulk price fetches

Previously, any single card for a batch would compromise the entire set
of prices. This allows up to 1/3 of a bulk fetch to fail.

closes #11

common/priceDB/bulk.go

@@ -2,22 +2,41 @@ package priceDB
 
 import (
 	"github.com/jackc/pgx"
+
+	"fmt"
 )
 
 func GetBulkLatestLowest(pool *pgx.ConnPool,
 	names []string, source string) (Prices, error) {
 
 	result:= make(Prices, len(names))
 
+	failed:= 0
+
 	for i, c:= range names {
 		p, err:= GetCardLatestLowest(pool, c, source)
 		if err!=nil {
-			return nil, err
+			// Record this as a failure
+			failed++
+
+			// Insert a placeholder
+			p = Price{
+				Name: c,
+				Set: "Unknown",
+				Price: -1,
+				Source: source,
+			}
 		}
 
 		result[i] = p
 	}
 
+	// If we fail to fetch more than 1/3 of prices for this bulk
+	// set, we error out
+	if failed >= len(names) / 3 {
+		return nil, fmt.Errorf("too many fetch failures")
+	}
+
 	return result, nil
 }
 
@@ -26,14 +45,31 @@ func GetBulkLatestHighest(pool *pgx.ConnPool,
 
 	result:= make(Prices, len(names))
 
+	failed:= 0
+
 	for i, c:= range names {
 		p, err:= GetCardLatestHighest(pool, c, source)
 		if err!=nil {
-			return nil, err
+			// Record this as a failure
+			failed++
+
+			// Insert a placeholder
+			p = Price{
+				Name: c,
+				Set: "Unknown",
+				Price: -1,
+				Source: source,
+			}
 		}
 
 		result[i] = p
 	}
 
+	// If we fail to fetch more than 1/3 of prices for this bulk
+	// set, we error out
+	if failed >= len(names) / 3 {
+		return nil, fmt.Errorf("too many fetch failures")
+	}
+
 	return result, nil
 }