From 8d051a14e5d9f3918b428791c249925b54c51115 Mon Sep 17 00:00:00 2001
From: mappu <mappu04@gmail.com>
Date: Sun, 30 Jun 2024 13:11:54 +1200
Subject: [PATCH] orderedkv: initial commit

---
 sqliteclidriver/orderedkv.go      | 85 +++++++++++++++++++++++++++++++
 sqliteclidriver/orderedkv_test.go | 30 +++++++++++
 2 files changed, 115 insertions(+)
 create mode 100644 sqliteclidriver/orderedkv.go
 create mode 100644 sqliteclidriver/orderedkv_test.go

diff --git a/sqliteclidriver/orderedkv.go b/sqliteclidriver/orderedkv.go
new file mode 100644
index 0000000..b6e90ef
--- /dev/null
+++ b/sqliteclidriver/orderedkv.go
@@ -0,0 +1,85 @@
+package sqliteclidriver
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+)
+
+type Pair struct {
+	Key   string
+	Value any
+}
+
+type OrderedKV []Pair
+
+func (o *OrderedKV) UnmarshalJSON(data []byte) error {
+	// Rough estimate malloc size based on number of `:`
+	// This is a lower bound since there might be nested elements
+	var elCount int64
+	for _, c := range data {
+		if c == ':' {
+			elCount += 1
+		}
+	}
+
+	*o = make([]Pair, 0, elCount)
+
+	// Parse the initial opening { delimiter from the JSON stream
+
+	reader := bytes.NewReader(data)
+	dec := json.NewDecoder(reader)
+
+	tok, err := dec.Token()
+	if err != nil {
+		return fmt.Errorf("expected '{': %w", err)
+	}
+	if d, ok := tok.(json.Delim); !ok || (rune(d) != '{') {
+		return fmt.Errorf("expected '{', got %v", tok)
+	}
+
+	// Read remaining content
+
+	for dec.More() {
+
+		var p Pair
+
+		// Parse key: either string or Delim('}')
+		tok, err := dec.Token()
+		if err != nil {
+			return fmt.Errorf("expected '{': %w", err)
+		}
+		switch tok := tok.(type) {
+		case json.Delim:
+			if rune(tok) == '}' {
+				// Finished
+				break
+			}
+			// Something else
+			return fmt.Errorf("expected string or }, got %v", tok)
+
+		case string:
+			// Valid key
+			p.Key = tok
+
+		default:
+			return fmt.Errorf("expected string or }, got %v", tok)
+		}
+
+		// Parse value (any)
+		err = dec.Decode(&p.Value)
+		if err != nil {
+			return err
+		}
+
+		*o = append(*o, p)
+	}
+
+	// Assert that there is no remaining content
+	if reader.Len() != 0 {
+		return fmt.Errorf("Unexpected trailing data (%d bytes remaining)", reader.Len())
+	}
+
+	// Done
+	return nil
+}
diff --git a/sqliteclidriver/orderedkv_test.go b/sqliteclidriver/orderedkv_test.go
new file mode 100644
index 0000000..5b50109
--- /dev/null
+++ b/sqliteclidriver/orderedkv_test.go
@@ -0,0 +1,30 @@
+package sqliteclidriver
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestOrderedKV(t *testing.T) {
+
+	input := `
+{
+	"zzz": "foo",
+	"aaa": "bar"
+}
+`
+	var got OrderedKV
+	err := json.Unmarshal([]byte(input), &got)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	expect := OrderedKV{
+		Pair{Key: "zzz", Value: "foo"},
+		Pair{Key: "aaa", Value: "bar"},
+	}
+
+	require.EqualValues(t, expect, got)
+}