package simplelog

import (
	"bytes"
	"context"
	"fmt"
	"log/slog"
	"runtime"
	"strings"
	"testing"
	"time"
)

// These tests sit inside the package so they can read the console line
// from a buffer instead of from stdout.

// lineOf calls logCall and returns "file:line" for the line lineOf was
// called from. Each test writes its log call inside logCall on that same
// line, so the result is the location the console line must name.
func lineOf(logCall func()) string {
	_, file, line, _ := runtime.Caller(1)

	logCall()

	return fmt.Sprintf("%s:%d", file, line)
}

// wantLocation fails the test unless the console line names location as
// where the record "casting" was logged.
func wantLocation(t *testing.T, output, location string) {
	t.Helper()

	if !strings.Contains(output, location+": casting") {
		t.Fatalf("console line %q does not name %s", output, location)
	}
}

// The default handler as simplelog installs it when stdout is a terminal:
// a MultiplexHandler holding a ConsoleHandler.
func TestConsoleHandlerNamesCallSiteThroughDefaultHandler(t *testing.T) {
	t.Parallel()

	var output bytes.Buffer

	logger := slog.New(&MultiplexHandler{handlers: []ExtendedHandler{
		&ConsoleHandler{out: &output},
	}})

	want := lineOf(func() { logger.Info("casting") })

	wantLocation(t, output.String(), want)
}

func TestConsoleHandlerNamesCallSiteUsedWithSlogNew(t *testing.T) {
	t.Parallel()

	var output bytes.Buffer

	logger := slog.New(&ConsoleHandler{out: &output})

	want := lineOf(func() { logger.Info("casting") })

	wantLocation(t, output.String(), want)
}

// The record is built as the log/slog package documentation shows for a
// function that logs on its caller's behalf: runtime.Callers supplies the
// PC.
func TestConsoleHandlerNamesCallSiteOfRecordPassedToHandle(t *testing.T) {
	t.Parallel()

	var (
		output bytes.Buffer
		pcs    [1]uintptr
	)

	want := lineOf(func() { runtime.Callers(1, pcs[:]) })

	record := slog.NewRecord(time.Now(), slog.LevelInfo, "casting", pcs[0])

	err := (&ConsoleHandler{out: &output}).Handle(context.Background(), record)
	if err != nil {
		t.Fatalf("Handle: %v", err)
	}

	wantLocation(t, output.String(), want)
}

func TestConsoleHandlerPrintsPlaceholderWithoutPC(t *testing.T) {
	t.Parallel()

	var output bytes.Buffer

	record := slog.NewRecord(time.Now(), slog.LevelInfo, "casting", 0)

	err := (&ConsoleHandler{out: &output}).Handle(context.Background(), record)
	if err != nil {
		t.Fatalf("Handle: %v", err)
	}

	wantLocation(t, output.String(), "???:0")
}