From 2c935642f6aa3db2df3f48f81e80b37740512679 Mon Sep 17 00:00:00 2001
From: Chenyu Zhao <zchenyu92@gmail.com>
Date: Wed, 18 May 2022 03:34:03 -0400
Subject: [PATCH] Make Deck satisfy the sql.Scanner interface

---
 card.go      | 22 ++++++++++++++++++----
 card_test.go |  7 +++++++
 deck.go      | 21 +++++++++++++++++++++
 3 files changed, 46 insertions(+), 4 deletions(-)

diff --git a/card.go b/card.go
index f05f2e5..06affa6 100644
--- a/card.go
+++ b/card.go
@@ -1,5 +1,9 @@
 package cards
 
+import (
+	"errors"
+)
+
 type Card int32
 
 var (
@@ -53,22 +57,32 @@ func NewCard(s string) Card {
 
 func NewCards(s string) []Card {
 	cards := []Card{}
-  for i := 0; i < len(s); i += 2 {
-    cards = append(cards, NewCard(s[i:i+2]))
-  }
-  return cards
+	for i := 0; i < len(s); i += 2 {
+		cards = append(cards, NewCard(s[i:i+2]))
+	}
+	return cards
 }
 
 func (c Card) MarshalText() ([]byte, error) {
 	return []byte(c.String()), nil
 }
 
+func (c *Card) UnmarshalText(text []byte) error {
+	if len(text) != 2 {
+		return errors.New("must have len 2")
+	}
+	*c = NewCard(string(text))
+	// TODO: validate
+	return nil
+}
+
 func (c Card) MarshalJSON() ([]byte, error) {
 	return []byte("\"" + c.String() + "\""), nil
 }
 
 func (c *Card) UnmarshalJSON(b []byte) error {
 	*c = NewCard(string(b[1:3]))
+	// TODO: validate
 	return nil
 }
 
diff --git a/card_test.go b/card_test.go
index 7ac97fc..6d06d93 100644
--- a/card_test.go
+++ b/card_test.go
@@ -32,6 +32,13 @@ func TestMarshalText(t *testing.T) {
 	assert.Equal(t, "Ah", string(b))
 }
 
+func TestUnmarshalText(t *testing.T) {
+	var c Card
+	assert.Nil(t, c.UnmarshalText([]byte("Ah")))
+	assert.Equal(t, NewCard("Ah"), c)
+	assert.Error(t, c.UnmarshalText([]byte("Ahh")), "must have len 2")
+}
+
 func TestMarshalJSON(t *testing.T) {
 	cards := []Card{
 		NewCard("Ah"),
diff --git a/deck.go b/deck.go
index bb49c7f..e865b0b 100644
--- a/deck.go
+++ b/deck.go
@@ -1,6 +1,8 @@
 package cards
 
 import (
+	"errors"
+	"fmt"
 	"math/rand"
 	"time"
 )
@@ -62,6 +64,25 @@ func (deck *Deck) Empty() bool {
 	return len(deck.cards) == 0
 }
 
+// Scan implements the Scanner interface.
+func (deck *Deck) Scan(src interface{}) error {
+	switch v := src.(type) {
+	case string:
+		if len(v)%2 != 0 {
+			return errors.New("string must have even length")
+		}
+		deck.cards = make([]Card, len(v)/2)
+		for i := 0; i < len(v); i += 2 {
+			if err := deck.cards[i/2].UnmarshalText([]byte(v)); err != nil {
+				return fmt.Errorf("Could not unmarshal card '%s': %v", v[i:i+2], err)
+			}
+		}
+		return nil
+	default:
+		return errors.New("must be `string` type")
+	}
+}
+
 func initializeFullCards() []Card {
 	var cards []Card