package circuitbreaker

import (
	"context"
	"errors"
	"fmt"
	"testing"
	"time"

	"github.com/afex/hystrix-go/hystrix"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
)

const success = "Success"

func TestCircuitBreaker_ExecuteSuccessSingle(t *testing.T) {
	cb := NewCircuitBreaker(Config{
		Timeout:                1000,
		MaxConcurrentRequests:  100,
		RequestVolumeThreshold: 10,
		SleepWindow:            10,
		ErrorPercentThreshold:  10,
	})

	expectedResult := success
	circuitName := "SuccessSingle"
	cmd := NewCommand(context.TODO(), []*Functor{
		NewFunctor(func() ([]interface{}, error) {
			return []any{expectedResult}, nil
		}, circuitName)},
	)

	result := cb.Execute(cmd)
	require.NoError(t, result.Error())
	require.Equal(t, expectedResult, result.Result()[0].(string))
}

func TestCircuitBreaker_ExecuteMultipleFallbacksFail(t *testing.T) {
	cb := NewCircuitBreaker(Config{
		Timeout:                10,
		MaxConcurrentRequests:  100,
		RequestVolumeThreshold: 10,
		SleepWindow:            10,
		ErrorPercentThreshold:  10,
	})

	circuitName := fmt.Sprintf("ExecuteMultipleFallbacksFail_%d", time.Now().Nanosecond()) // unique name to avoid conflicts with go tests `-count` option
	errSecProvFailed := errors.New("provider 2 failed")
	errThirdProvFailed := errors.New("provider 3 failed")
	cmd := NewCommand(context.TODO(), []*Functor{
		NewFunctor(func() ([]interface{}, error) {
			time.Sleep(100 * time.Millisecond) // will cause hystrix: timeout
			return []any{success}, nil
		}, circuitName+"1"),
		NewFunctor(func() ([]interface{}, error) {
			return nil, errSecProvFailed
		}, circuitName+"2"),
		NewFunctor(func() ([]interface{}, error) {
			return nil, errThirdProvFailed
		}, circuitName+"3"),
	})

	result := cb.Execute(cmd)
	require.Error(t, result.Error())
	assert.True(t, errors.Is(result.Error(), hystrix.ErrTimeout))
	assert.True(t, errors.Is(result.Error(), errSecProvFailed))
	assert.True(t, errors.Is(result.Error(), errThirdProvFailed))
}

func TestCircuitBreaker_ExecuteMultipleFallbacksFailButLastSuccessStress(t *testing.T) {
	cb := NewCircuitBreaker(Config{
		Timeout:                10,
		MaxConcurrentRequests:  100,
		RequestVolumeThreshold: 10,
		SleepWindow:            10,
		ErrorPercentThreshold:  10,
	})

	expectedResult := success
	circuitName := fmt.Sprintf("LastSuccessStress_%d", time.Now().Nanosecond()) // unique name to avoid conflicts with go tests `-count` option

	// These are executed sequentially, but I had an issue with the test failing
	// because of the open circuit
	for i := 0; i < 1000; i++ {
		cmd := NewCommand(context.TODO(), []*Functor{
			NewFunctor(func() ([]interface{}, error) {
				return nil, errors.New("provider 1 failed")
			}, circuitName+"1"),
			NewFunctor(func() ([]interface{}, error) {
				return nil, errors.New("provider 2 failed")
			}, circuitName+"2"),
			NewFunctor(func() ([]interface{}, error) {
				return []any{expectedResult}, nil
			}, circuitName+"3"),
		},
		)

		result := cb.Execute(cmd)
		require.NoError(t, result.Error())
		require.Equal(t, expectedResult, result.Result()[0].(string))
	}
}

func TestCircuitBreaker_ExecuteSwitchToWorkingProviderOnVolumeThresholdReached(t *testing.T) {
	cb := NewCircuitBreaker(Config{
		RequestVolumeThreshold: 10,
	})

	expectedResult := success
	circuitName := fmt.Sprintf("SwitchToWorkingProviderOnVolumeThresholdReached_%d", time.Now().Nanosecond()) // unique name to avoid conflicts with go tests `-count` option

	prov1Called := 0
	prov2Called := 0
	prov3Called := 0
	// These are executed sequentially
	for i := 0; i < 20; i++ {
		cmd := NewCommand(context.TODO(), []*Functor{
			NewFunctor(func() ([]interface{}, error) {
				prov1Called++
				return nil, errors.New("provider 1 failed")
			}, circuitName+"1"),
			NewFunctor(func() ([]interface{}, error) {
				prov2Called++
				return nil, errors.New("provider 2 failed")
			}, circuitName+"2"),
			NewFunctor(func() ([]interface{}, error) {
				prov3Called++
				return []any{expectedResult}, nil
			}, circuitName+"3"),
		})

		result := cb.Execute(cmd)
		require.NoError(t, result.Error())
		require.Equal(t, expectedResult, result.Result()[0].(string))
	}

	assert.Equal(t, 10, prov1Called)
	assert.Equal(t, 10, prov2Called)
	assert.Equal(t, 20, prov3Called)
}

func TestCircuitBreaker_ExecuteHealthCheckOnWindowTimeout(t *testing.T) {
	sleepWindow := 10
	cb := NewCircuitBreaker(Config{
		RequestVolumeThreshold: 1, // 1 failed request is enough to trip the circuit
		SleepWindow:            sleepWindow,
		ErrorPercentThreshold:  1, // Trip on first error
	})

	expectedResult := success
	circuitName := fmt.Sprintf("SwitchToWorkingProviderOnWindowTimeout_%d", time.Now().Nanosecond()) // unique name to avoid conflicts with go tests `-count` option

	prov1Called := 0
	prov2Called := 0
	// These are executed sequentially
	for i := 0; i < 10; i++ {
		cmd := NewCommand(context.TODO(), []*Functor{
			NewFunctor(func() ([]interface{}, error) {
				prov1Called++
				return nil, errors.New("provider 1 failed")
			}, circuitName+"1"),
			NewFunctor(func() ([]interface{}, error) {
				prov2Called++
				return []any{expectedResult}, nil
			}, circuitName+"2"),
		})

		result := cb.Execute(cmd)
		require.NoError(t, result.Error())
		require.Equal(t, expectedResult, result.Result()[0].(string))
	}

	assert.Less(t, prov1Called, 3) // most of the time only 1 call is made, but occasionally 2 can happen
	assert.Equal(t, 10, prov2Called)
	assert.True(t, CircuitExists(circuitName+"1"))
	assert.True(t, IsCircuitOpen(circuitName+"1"))

	// Wait for the sleep window to expire
	time.Sleep(time.Duration(sleepWindow+1) * time.Millisecond)
	cmd := NewCommand(context.TODO(), []*Functor{
		NewFunctor(func() ([]interface{}, error) {
			prov1Called++
			return []any{expectedResult}, nil // Now it is working
		}, circuitName+"1"),
		NewFunctor(func() ([]interface{}, error) {
			prov2Called++
			return []any{expectedResult}, nil
		}, circuitName+"2"),
	})
	result := cb.Execute(cmd)
	require.NoError(t, result.Error())

	assert.Less(t, prov1Called, 4) // most of the time only 2 calls are made, but occasionally 3 can happen
	assert.Equal(t, 10, prov2Called)
}

func TestCircuitBreaker_CommandCancel(t *testing.T) {
	cb := NewCircuitBreaker(Config{})

	circuitName := fmt.Sprintf("CommandCancel_%d", time.Now().Nanosecond()) // unique name to avoid conflicts with go tests `-count` option

	prov1Called := 0
	prov2Called := 0

	var ctx context.Context
	expectedErr := errors.New("provider 1 failed")

	cmd := NewCommand(ctx, nil)
	cmd.Add(NewFunctor(func() ([]interface{}, error) {
		prov1Called++
		cmd.Cancel()
		return nil, expectedErr
	}, circuitName+"1"))
	cmd.Add(NewFunctor(func() ([]interface{}, error) {
		prov2Called++
		return nil, errors.New("provider 2 failed")
	}, circuitName+"2"))

	result := cb.Execute(cmd)
	require.True(t, errors.Is(result.Error(), expectedErr))

	assert.Equal(t, 1, prov1Called)
	assert.Equal(t, 0, prov2Called)
}

func TestCircuitBreaker_EmptyOrNilCommand(t *testing.T) {
	cb := NewCircuitBreaker(Config{})
	cmd := NewCommand(context.TODO(), nil)
	result := cb.Execute(cmd)
	require.Error(t, result.Error())
	result = cb.Execute(nil)
	require.Error(t, result.Error())
}

func TestCircuitBreaker_CircuitExistsAndClosed(t *testing.T) {
	timestamp := time.Now().Nanosecond()
	nonExCircuit := fmt.Sprintf("nonexistent_%d", timestamp) // unique name to avoid conflicts with go tests `-count` option
	require.False(t, CircuitExists(nonExCircuit))

	cb := NewCircuitBreaker(Config{})
	cmd := NewCommand(context.TODO(), nil)
	existCircuit := fmt.Sprintf("existing_%d", timestamp) // unique name to avoid conflicts with go tests `-count` option
	// We add it twice as otherwise it's only used for the fallback
	cmd.Add(NewFunctor(func() ([]interface{}, error) {
		return nil, nil
	}, existCircuit))

	cmd.Add(NewFunctor(func() ([]interface{}, error) {
		return nil, nil
	}, existCircuit))
	_ = cb.Execute(cmd)
	require.True(t, CircuitExists(existCircuit))
	require.False(t, IsCircuitOpen(existCircuit))
}

func TestCircuitBreaker_Fallback(t *testing.T) {
	cb := NewCircuitBreaker(Config{
		RequestVolumeThreshold: 1, // 1 failed request is enough to trip the circuit
		SleepWindow:            50000,
		ErrorPercentThreshold:  1, // Trip on first error
	})

	circuitName := fmt.Sprintf("Fallback_%d", time.Now().Nanosecond()) // unique name to avoid conflicts with go tests `-count` option

	prov1Called := 0

	var ctx context.Context
	expectedErr := errors.New("provider 1 failed")

	// we start with 2, and we open the first
	for {
		cmd := NewCommand(ctx, nil)
		cmd.Add(NewFunctor(func() ([]interface{}, error) {
			return nil, expectedErr
		}, circuitName+"1"))
		cmd.Add(NewFunctor(func() ([]interface{}, error) {
			return nil, errors.New("provider 2 failed")
		}, circuitName+"2"))

		result := cb.Execute(cmd)
		require.NotNil(t, result.Error())
		if IsCircuitOpen(circuitName + "1") {
			break
		}
	}

	// Make sure circuit is open
	require.True(t, CircuitExists(circuitName+"1"))
	require.True(t, IsCircuitOpen(circuitName+"1"))

	// we send a single request, it should hit the provider, at that's a fallback
	cmd := NewCommand(ctx, nil)
	cmd.Add(NewFunctor(func() ([]interface{}, error) {
		prov1Called++
		return nil, expectedErr
	}, circuitName+"1"))

	result := cb.Execute(cmd)
	require.True(t, errors.Is(result.Error(), expectedErr))

	assert.Equal(t, 1, prov1Called)
}