package runtimeinfo

import (
	"runtime/debug"
	"sync"
	"sync/atomic"
	"testing"
)

func TestVersion(t *testing.T) {
	tests := []struct {
		name     string
		injected string
		info     *debug.BuildInfo
		ok       bool
		want     string
	}{
		{
			name:     "injected version takes precedence",
			injected: "v1.2.3",
			info:     &debug.BuildInfo{Main: debug.Module{Version: "v4.5.6"}},
			ok:       true,
			want:     "v1.2.3",
		},
		{
			name: "main module version",
			info: &debug.BuildInfo{Main: debug.Module{Version: "v4.5.6"}},
			ok:   true,
			want: "v4.5.6",
		},
		{
			name: "missing build information",
			want: "dev",
		},
		{
			name: "development main module",
			info: &debug.BuildInfo{Main: debug.Module{Version: "(devel)"}},
			ok:   true,
			want: "dev",
		},
		{
			name: "empty main module version",
			info: &debug.BuildInfo{Main: debug.Module{}},
			ok:   true,
			want: "dev",
		},
	}

	for _, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			got := version(test.injected, func() (*debug.BuildInfo, bool) {
				return test.info, test.ok
			})
			if got != test.want {
				t.Fatalf("version() = %q, want %q", got, test.want)
			}
		})
	}
}

func TestFallbackVersionReadsMetadataOnceConcurrently(t *testing.T) {
	var reads atomic.Int32
	fallback := newFallbackVersion(func() (*debug.BuildInfo, bool) {
		reads.Add(1)
		return &debug.BuildInfo{Main: debug.Module{Version: "v4.5.6"}}, true
	})

	const callers = 32
	results := make(chan string, callers)
	var workers sync.WaitGroup
	workers.Add(callers)
	for i := 0; i < callers; i++ {
		go func() {
			defer workers.Done()
			results <- fallback()
		}()
	}
	workers.Wait()
	close(results)
	for result := range results {
		if result != "v4.5.6" {
			t.Errorf("fallback() = %q, want stable version", result)
		}
	}
	if got := reads.Load(); got != 1 {
		t.Fatalf("metadata reader called %d times, want once", got)
	}
}

func TestFallbackVersionCachesUnavailableAndDevelopmentMetadata(t *testing.T) {
	for _, test := range []struct {
		name string
		read func() (*debug.BuildInfo, bool)
	}{
		{name: "unavailable", read: func() (*debug.BuildInfo, bool) { return nil, false }},
		{name: "development", read: func() (*debug.BuildInfo, bool) {
			return &debug.BuildInfo{Main: debug.Module{Version: "(devel)"}}, true
		}},
	} {
		t.Run(test.name, func(t *testing.T) {
			fallback := newFallbackVersion(test.read)
			if got := fallback(); got != "dev" {
				t.Fatalf("fallback() = %q, want dev", got)
			}
			if got := fallback(); got != "dev" {
				t.Fatalf("repeated fallback() = %q, want dev", got)
			}
		})
	}
}