package config_test

import (
	"os"
	"testing"
	"time"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"
	"go.uber.org/fx"
	"go.uber.org/fx/fxtest"
	"sneak.berlin/go/webhooker/internal/config"
	"sneak.berlin/go/webhooker/internal/globals"
	"sneak.berlin/go/webhooker/internal/logger"
)

// Shared subtest names for the env-parsing tables below, which all
// exercise the same three cases against different variables.
const (
	caseUnsetUsesDefault = "unset uses default"
	caseValidValueParsed = "valid value is parsed"
	caseUnparseableFails = "unparseable value fails startup"

	// cidrPrivateV4 is the sample trusted-proxy block the
	// TRUSTED_PROXIES cases are built from.
	cidrPrivateV4 = "10.0.0.0/8"
)

func TestEnvironmentConfig(t *testing.T) {
	tests := []struct {
		name        string
		envValue    string
		envVars     map[string]string
		expectError bool
		isDev       bool
		isProd      bool
	}{
		{
			name:   "default is dev",
			isDev:  true,
			isProd: false,
		},
		{
			name:     "explicit dev",
			envValue: "dev",
			isDev:    true,
			isProd:   false,
		},
		{
			name:     "explicit prod",
			envValue: "prod",
			isDev:    false,
			isProd:   true,
		},
		{
			name:        "invalid environment",
			envValue:    "staging",
			expectError: true,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			// Cannot use t.Parallel() here because t.Setenv
			// is incompatible with parallel subtests.
			if tt.envValue != "" {
				t.Setenv(
					"WEBHOOKER_ENVIRONMENT", tt.envValue,
				)
			} else {
				require.NoError(t, os.Unsetenv(
					"WEBHOOKER_ENVIRONMENT",
				))
			}

			for k, v := range tt.envVars {
				t.Setenv(k, v)
			}

			if tt.expectError {
				testEnvironmentConfigError(t)
			} else {
				testEnvironmentConfigSuccess(
					t, tt.isDev, tt.isProd,
				)
			}
		})
	}
}

func testEnvironmentConfigError(t *testing.T) {
	t.Helper()

	var cfg *config.Config

	app := fx.New(
		fx.NopLogger,
		fx.Provide(
			globals.New,
			logger.New,
			config.New,
		),
		fx.Populate(&cfg),
	)

	assert.Error(t, app.Err())
}

func testEnvironmentConfigSuccess(
	t *testing.T,
	isDev, isProd bool,
) {
	t.Helper()

	var cfg *config.Config

	app := fxtest.New(
		t,
		fx.Provide(
			globals.New,
			logger.New,
			config.New,
		),
		fx.Populate(&cfg),
	)
	require.NoError(t, app.Err())

	app.RequireStart()

	defer app.RequireStop()

	assert.Equal(t, isDev, cfg.IsDev())
	assert.Equal(t, isProd, cfg.IsProd())
}

func TestRetentionSweepInterval(t *testing.T) {
	tests := []struct {
		name        string
		set         bool
		value       string
		expectError bool
		expected    time.Duration
	}{
		{
			name:     caseUnsetUsesDefault,
			set:      false,
			expected: time.Hour,
		},
		{
			name:     caseValidValueParsed,
			set:      true,
			value:    "15m",
			expected: 15 * time.Minute,
		},
		{
			name:        caseUnparseableFails,
			set:         true,
			value:       "not-a-duration",
			expectError: true,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			// Cannot use t.Parallel() here because t.Setenv
			// is incompatible with parallel subtests.
			t.Setenv("WEBHOOKER_ENVIRONMENT", "dev")

			if tt.set {
				t.Setenv("RETENTION_SWEEP_INTERVAL", tt.value)
			} else {
				require.NoError(t, os.Unsetenv(
					"RETENTION_SWEEP_INTERVAL",
				))
			}

			if tt.expectError {
				expectStartupError(t)
			} else {
				testRetentionSweepIntervalSuccess(t, tt.expected)
			}
		})
	}
}

// startupError builds the app config.New belongs to and returns
// the error fx reports, which is non-nil whenever an environment
// value is set but invalid.
func startupError(t *testing.T) error {
	t.Helper()

	var cfg *config.Config

	app := fx.New(
		fx.NopLogger,
		fx.Provide(
			globals.New,
			logger.New,
			config.New,
		),
		fx.Populate(&cfg),
	)

	return app.Err()
}

// expectStartupError asserts that fx refuses to build the app,
// which is what a set-but-invalid environment value must cause.
func expectStartupError(t *testing.T) {
	t.Helper()

	assert.Error(t, startupError(t))
}

// expectStartupErrorFor asserts that startup fails, that the error
// names the offending variable so an operator can find it, and,
// when sentinel is non-nil, that it wraps that sentinel.
func expectStartupErrorFor(
	t *testing.T,
	key string,
	sentinel error,
) {
	t.Helper()

	err := startupError(t)
	require.ErrorContains(t, err, key)

	if sentinel != nil {
		require.ErrorIs(t, err, sentinel)
	}
}

func testRetentionSweepIntervalSuccess(
	t *testing.T,
	expected time.Duration,
) {
	t.Helper()

	var cfg *config.Config

	app := fxtest.New(
		t,
		fx.Provide(
			globals.New,
			logger.New,
			config.New,
		),
		fx.Populate(&cfg),
	)
	require.NoError(t, app.Err())

	app.RequireStart()

	defer app.RequireStop()

	assert.Equal(t, expected, cfg.RetentionSweepInterval)
}

func TestSessionIdleTimeout(t *testing.T) {
	tests := []struct {
		name        string
		set         bool
		value       string
		expectError bool
		expected    time.Duration
	}{
		{
			name:     caseUnsetUsesDefault,
			set:      false,
			expected: 24 * time.Hour,
		},
		{
			name:     caseValidValueParsed,
			set:      true,
			value:    "30m",
			expected: 30 * time.Minute,
		},
		{
			name:        caseUnparseableFails,
			set:         true,
			value:       "not-a-duration",
			expectError: true,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			// Cannot use t.Parallel() here because t.Setenv
			// is incompatible with parallel subtests.
			t.Setenv("WEBHOOKER_ENVIRONMENT", "dev")

			if tt.set {
				t.Setenv("SESSION_IDLE_TIMEOUT", tt.value)
			} else {
				require.NoError(t, os.Unsetenv(
					"SESSION_IDLE_TIMEOUT",
				))
			}

			if tt.expectError {
				expectStartupError(t)
			} else {
				testSessionIdleTimeoutSuccess(t, tt.expected)
			}
		})
	}
}

func testSessionIdleTimeoutSuccess(
	t *testing.T,
	expected time.Duration,
) {
	t.Helper()

	var cfg *config.Config

	app := fxtest.New(
		t,
		fx.Provide(
			globals.New,
			logger.New,
			config.New,
		),
		fx.Populate(&cfg),
	)
	require.NoError(t, app.Err())

	app.RequireStart()

	defer app.RequireStop()

	assert.Equal(t, expected, cfg.SessionIdleTimeout)
}

func TestDefaultDataDir(t *testing.T) {
	for _, env := range []string{"", "dev", "prod"} {
		name := env
		if name == "" {
			name = "unset"
		}

		t.Run("env="+name, func(t *testing.T) {
			// Cannot use t.Parallel() here because t.Setenv
			// is incompatible with parallel subtests.
			if env != "" {
				t.Setenv("WEBHOOKER_ENVIRONMENT", env)
			} else {
				require.NoError(t, os.Unsetenv(
					"WEBHOOKER_ENVIRONMENT",
				))
			}

			require.NoError(t, os.Unsetenv("DATA_DIR"))

			var cfg *config.Config

			app := fxtest.New(
				t,
				fx.Provide(
					globals.New,
					logger.New,
					config.New,
				),
				fx.Populate(&cfg),
			)
			require.NoError(t, app.Err())

			app.RequireStart()

			defer app.RequireStop()

			assert.Equal(
				t, "/var/lib/webhooker", cfg.DataDir,
			)
		})
	}
}

func TestReceiverRateLimit(t *testing.T) {
	tests := []struct {
		name        string
		set         bool
		value       string
		expectError bool
		// sentinel, when set, must be wrapped by the startup
		// error; every error case must additionally name the
		// variable in its message.
		sentinel error
		expected int
	}{
		{
			name:     caseUnsetUsesDefault,
			set:      false,
			expected: 120,
		},
		{
			name:     caseValidValueParsed,
			set:      true,
			value:    "30",
			expected: 30,
		},
		{
			name:        caseUnparseableFails,
			set:         true,
			value:       "not-a-number",
			expectError: true,
		},
		{
			name:        "zero fails startup",
			set:         true,
			value:       "0",
			expectError: true,
			sentinel:    config.ErrNonPositiveValue,
		},
		{
			name:        "negative fails startup",
			set:         true,
			value:       "-5",
			expectError: true,
			sentinel:    config.ErrNonPositiveValue,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			// Cannot use t.Parallel() here because t.Setenv
			// is incompatible with parallel subtests.
			t.Setenv("WEBHOOKER_ENVIRONMENT", "dev")

			if tt.set {
				t.Setenv("RECEIVER_RATE_LIMIT", tt.value)
			} else {
				require.NoError(t, os.Unsetenv(
					"RECEIVER_RATE_LIMIT",
				))
			}

			if tt.expectError {
				expectStartupErrorFor(
					t, "RECEIVER_RATE_LIMIT", tt.sentinel,
				)
			} else {
				testReceiverRateLimitSuccess(t, tt.expected)
			}
		})
	}
}

func testReceiverRateLimitSuccess(
	t *testing.T,
	expected int,
) {
	t.Helper()

	var cfg *config.Config

	app := fxtest.New(
		t,
		fx.Provide(
			globals.New,
			logger.New,
			config.New,
		),
		fx.Populate(&cfg),
	)
	require.NoError(t, app.Err())

	app.RequireStart()

	defer app.RequireStop()

	assert.Equal(t, expected, cfg.ReceiverRateLimit)
}

func TestTrustedProxies(t *testing.T) {
	tests := []struct {
		name        string
		set         bool
		value       string
		expectError bool
		expected    []string
	}{
		{
			// The default must be "trust nobody": an empty list
			// means forwarded headers are ignored, never that
			// every peer may speak for the client.
			name:     caseUnsetUsesDefault,
			set:      false,
			expected: []string{},
		},
		{
			name:     "blank value trusts nothing",
			set:      true,
			value:    "  ",
			expected: []string{},
		},
		{
			name:  caseValidValueParsed,
			set:   true,
			value: cidrPrivateV4 + ", 192.168.1.7 ,2001:db8::/32",
			expected: []string{
				cidrPrivateV4, "192.168.1.7/32", "2001:db8::/32",
			},
		},
		{
			name:     "host bits are masked off",
			set:      true,
			value:    "10.1.2.3/8",
			expected: []string{cidrPrivateV4},
		},
		{
			// Peer addresses are unmapped before they are
			// matched, so an IPv4-mapped prefix kept in that
			// form could never match anything.
			name:     "IPv4-mapped prefix is unmapped",
			set:      true,
			value:    "::ffff:10.0.0.0/104",
			expected: []string{cidrPrivateV4},
		},
		{
			name:        caseUnparseableFails,
			set:         true,
			value:       cidrPrivateV4 + ",not-an-address",
			expectError: true,
		},
		{
			name:        "out-of-range prefix length fails startup",
			set:         true,
			value:       "10.0.0.0/33",
			expectError: true,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			// Cannot use t.Parallel() here because t.Setenv
			// is incompatible with parallel subtests.
			t.Setenv("WEBHOOKER_ENVIRONMENT", "dev")

			if tt.set {
				t.Setenv("TRUSTED_PROXIES", tt.value)
			} else {
				require.NoError(t, os.Unsetenv("TRUSTED_PROXIES"))
			}

			if tt.expectError {
				expectStartupErrorFor(
					t, "TRUSTED_PROXIES", config.ErrInvalidCIDR,
				)
			} else {
				testTrustedProxiesSuccess(t, tt.expected)
			}
		})
	}
}

func testTrustedProxiesSuccess(
	t *testing.T,
	expected []string,
) {
	t.Helper()

	var cfg *config.Config

	app := fxtest.New(
		t,
		fx.Provide(
			globals.New,
			logger.New,
			config.New,
		),
		fx.Populate(&cfg),
	)
	require.NoError(t, app.Err())

	app.RequireStart()

	defer app.RequireStop()

	got := make([]string, 0, len(cfg.TrustedProxies))
	for _, prefix := range cfg.TrustedProxies {
		got = append(got, prefix.String())
	}

	assert.Equal(t, expected, got)
}