feat: add Statements, the top-level statement iterator

Assisted-by: GLM 5.3 Flash

interpres_test.go

@@ -5,10 +5,12 @@ package interpres
 
 import (
 	"errors"
+	"fmt"
 	"math"
 	"os"
 	"path/filepath"
 	"reflect"
+	"slices"
 	"strings"
 	"testing"
 	"time"
@@ -821,3 +823,65 @@ func TestZeroOffsetRoundTrip(t *testing.T) {
 		t.Errorf("a = %q, want 1979-05-27T07:32Z", got)
 	}
 }
+
+func TestStatements(t *testing.T) {
+	src := strings.NewReader(`title = "demo"
+port = 8080
+
+[server]
+host = "127.0.0.1"
+
+[[items]]
+name = "a"
+
+[[items]]
+name = "b"
+`)
+	var lines []string
+	for stmt, err := range Statements(src) {
+		if err != nil {
+			t.Fatal(err)
+		}
+		switch {
+		case stmt.Index >= 0:
+			lines = append(lines, fmt.Sprintf("%s #%d", stmt.Key, stmt.Index))
+		case stmt.Table != nil:
+			lines = append(lines, fmt.Sprintf("[%s] %v", stmt.Key, stmt.Table.Keys()))
+		default:
+			lines = append(lines, fmt.Sprintf("%s = %v", stmt.Key, stmt.Value))
+		}
+	}
+	want := []string{
+		`title = demo`,
+		`port = 8080`,
+		`[server] [host]`,
+		`items #0`,
+		`items #1`,
+	}
+	if !slices.Equal(lines, want) {
+		t.Errorf("statements =\n%v\nwant:\n%v", lines, want)
+	}
+
+	t.Run("breaking stops the iteration", func(t *testing.T) {
+		src := strings.NewReader("a = 1\nb = 2\nc = 3\n")
+		count := 0
+		for range Statements(src) {
+			count++
+			break
+		}
+		if count != 1 {
+			t.Errorf("iterated %d statements after break, want 1", count)
+		}
+	})
+	t.Run("a parse error arrives as the second value", func(t *testing.T) {
+		for stmt, err := range Statements(strings.NewReader("broken =\n")) {
+			if err == nil {
+				t.Fatalf("statement %+v without an error", stmt)
+			}
+			if _, ok := errors.AsType[*SyntaxError](err); !ok {
+				t.Errorf("err = %v, want a SyntaxError", err)
+			}
+			break
+		}
+	})
+}