package applog

import (
	"bytes"
	"encoding/json"
	"log/slog"
	"strings"
	"testing"
)

func TestNewLogger_FiltersBelowConfiguredLevel(t *testing.T) {
	var buf bytes.Buffer
	logger := NewLogger("warn", &buf)

	logger.Info("should be dropped")
	if buf.Len() != 0 {
		t.Fatalf("expected no output for an Info message under a warn-level logger, got %q", buf.String())
	}

	logger.Warn("should appear")
	if !strings.Contains(buf.String(), "should appear") {
		t.Fatalf("expected the Warn message in output, got %q", buf.String())
	}
}

func TestNewLogger_WritesValidJSON(t *testing.T) {
	var buf bytes.Buffer
	logger := NewLogger("info", &buf)
	logger.Info("hello", "key", "value")

	var decoded map[string]any
	if err := json.Unmarshal(buf.Bytes(), &decoded); err != nil {
		t.Fatalf("output is not valid JSON: %v (%q)", err, buf.String())
	}
	if decoded["msg"] != "hello" || decoded["key"] != "value" {
		t.Errorf("decoded = %+v, want msg=hello key=value", decoded)
	}
}

func TestNewLogger_OmitsEmptyMsg(t *testing.T) {
	var buf bytes.Buffer
	logger := NewLogger("info", &buf)
	logger.Info("", "type", "http", "status", 200)

	var decoded map[string]any
	if err := json.Unmarshal(buf.Bytes(), &decoded); err != nil {
		t.Fatalf("output not JSON: %v (%q)", err, buf.String())
	}
	if _, present := decoded["msg"]; present {
		t.Errorf("empty msg should be omitted, got %+v", decoded)
	}
	if decoded["type"] != "http" {
		t.Errorf("attrs lost alongside dropped msg: %+v", decoded)
	}
}

func TestApp_TagsMandatoryFields(t *testing.T) {
	var buf bytes.Buffer
	prev := slog.Default()
	slog.SetDefault(NewLogger("info", &buf))
	defer slog.SetDefault(prev)

	App("api.Server", "handleThing").Info("did it", "extra", 1)

	var decoded map[string]any
	if err := json.Unmarshal(buf.Bytes(), &decoded); err != nil {
		t.Fatalf("output not JSON: %v", err)
	}
	if decoded["type"] != "app" || decoded["class"] != "api.Server" || decoded["method"] != "handleThing" {
		t.Errorf("mandatory fields = %+v, want type=app class=api.Server method=handleThing", decoded)
	}
}