// Unless explicitly stated otherwise all files in this repository are licensed
// under the Apache License Version 2.0.
// This product includes software developed at Datadog (https://www.datadoghq.com/).
// Copyright 2016 Datadog, Inc.

package logs

import (
	"io"
	"os"
	"strconv"
	"testing"

	"github.com/stretchr/testify/assert"
)

// resetGlobalState is a helper that resets the package level variables that keep
// state between invocations. This is required so that each test can start with
// a clean slate and does not depend on execution order.
func resetGlobalState() {
	enabled = nil
	logsWriterInstance = nil
}

func TestIsEnabled_DefaultsToFalse(t *testing.T) {
	resetGlobalState()
	os.Unsetenv("DD_CIVISIBILITY_LOGS_ENABLED")

	assert.False(t, IsEnabled(), "IsEnabled should be false when the env var is not set")
}

func TestIsEnabled_EnvVarTrue(t *testing.T) {
	resetGlobalState()
	os.Setenv("DD_CIVISIBILITY_LOGS_ENABLED", "true")
	t.Cleanup(func() { os.Unsetenv("DD_CIVISIBILITY_LOGS_ENABLED") })

	assert.True(t, IsEnabled(), "IsEnabled should be true when the env var is set to true")
}

func TestInitializeAndStop(t *testing.T) {
	// Make sure feature is enabled
	resetGlobalState()
	os.Setenv("DD_CIVISIBILITY_LOGS_ENABLED", "true")
	t.Cleanup(func() { os.Unsetenv("DD_CIVISIBILITY_LOGS_ENABLED") })

	Initialize("my-awesome-service")
	assert.NotNil(t, logsWriterInstance, "logsWriterInstance should be set after Initialize")
	assert.Equal(t, "my-awesome-service", servName)
	assert.NotEmpty(t, host, "host should be detected during Initialize")

	Stop()
	assert.Nil(t, logsWriterInstance, "logsWriterInstance should be nil after Stop")
}

func TestWriteLog_WhenDisabled_NoOp(t *testing.T) {
	resetGlobalState()
	os.Unsetenv("DD_CIVISIBILITY_LOGS_ENABLED")

	// Call WriteLog – it should not panic and should not create a writer.
	WriteLog(123, "module", "suite", "test", "msg", "")
	assert.Nil(t, logsWriterInstance, "logsWriterInstance should remain nil when WriteLog is called while disabled")
}

func TestWriteLog_WritesEntry(t *testing.T) {
	resetGlobalState()
	os.Setenv("DD_CIVISIBILITY_LOGS_ENABLED", "true")
	t.Cleanup(func() { os.Unsetenv("DD_CIVISIBILITY_LOGS_ENABLED") })

	Initialize("writer-test-service")
	assert.NotNil(t, logsWriterInstance)

	WriteLog(42, "mod", "suite", "test", "hello", "tag:value")

	// Because WriteLog delegates to logsWriterInstance.add which, in turn,
	// stores the entry inside the payload, we can verify that the payload
	// now contains exactly one item.
	assert.Equal(t, 1, logsWriterInstance.payload.itemCount(), "Exactly one log entry should be stored after WriteLog")
}

func TestLogsPayloadResetAndRead(t *testing.T) {
	p := newLogsPayload()
	for i := range 5 {
		p.push(&logEntry{Message: "msg" + strconv.Itoa(i)})
	}

	// Read entire payload once.
	first, err := io.ReadAll(p)
	assert.NoError(t, err)
	assert.NotEmpty(t, first)

	// Reset and read again – bytes should match the first read.
	p.reset()
	second, err := io.ReadAll(p)
	assert.NoError(t, err)
	assert.Equal(t, first, second, "Payload contents should be identical after reset")
}

func TestLogsPayloadClear(t *testing.T) {
	p := newLogsPayload()
	p.push(&logEntry{Message: "msg"})

	assert.Greater(t, p.size(), 0, "Size should be > 0 after pushing an entry")

	p.clear()

	assert.Equal(t, 0, p.itemCount())
	assert.LessOrEqual(t, p.size(), 2, "Size should be minimal after clear")
}
