package config_test

import (
	"errors"
	"strings"
	"testing"
	"time"

	"github.com/spf13/viper"
	"sneak.berlin/go/simplexcalc/internal/config"
)

// Credentials used by the metrics-auth cases.
const (
	testUser = "scraper"
	testPass = "hunter2"
)

// env builds a viper instance holding exactly the given keys, so a test
// describes one environment without touching the process's.
func env(kv map[string]string) *viper.Viper {
	v := viper.New()
	for k, val := range kv {
		v.Set(k, val)
	}

	return v
}

// TestAbsentValuesTakeDefaults pins the other half of the iron rule: a
// value that is not set does get the default. Without this, a bug that
// rejected everything would pass every test below.
func TestAbsentValuesTakeDefaults(t *testing.T) {
	t.Parallel()

	c, err := config.Load(env(nil))
	if err != nil {
		t.Fatalf("empty environment must be valid, got: %v", err)
	}

	if c.Port != int(config.DefaultPort) {
		t.Errorf("Port = %d, want %d", c.Port, config.DefaultPort)
	}

	if c.MaxRequestBody != config.DefaultMaxRequestBody {
		t.Errorf("MaxRequestBody = %d, want %d",
			c.MaxRequestBody, config.DefaultMaxRequestBody)
	}

	if c.RequestTimeout != config.DefaultRequestTimeout {
		t.Errorf("RequestTimeout = %s, want %s",
			c.RequestTimeout, config.DefaultRequestTimeout)
	}

	if !c.HSTS {
		t.Error("HSTS must default on when DEBUG is not set")
	}

	if !c.CSRFKeyEphemeral {
		t.Error("an absent CSRF_KEY must mark the config for an ephemeral key")
	}
}

// TestSetButUnparseableAborts is the central contract of this package.
// Every case is a value an operator plausibly types, and every one of
// them must fail startup rather than be replaced by the default.
func TestSetButUnparseableAborts(t *testing.T) {
	t.Parallel()

	cases := map[string]map[string]string{
		"port is not a number":     {config.EnvPort: "eighty"},
		"port is zero":             {config.EnvPort: "0"},
		"port is above the range":  {config.EnvPort: "70000"},
		"port is a float":          {config.EnvPort: "8080.0"},
		"debug is yes":             {config.EnvDebug: "yes"},
		"hsts is on":               {config.EnvHSTS: "on"},
		"body cap is nonsense":     {config.EnvMaxRequestBody: "big"},
		"body cap is too large":    {config.EnvMaxRequestBody: "1TiB"},
		"body cap is too small":    {config.EnvMaxRequestBody: "10"},
		"timeout has no unit":      {config.EnvRequestTimeout: "30"},
		"timeout is out of range":  {config.EnvRequestTimeout: "1h"},
		"grace is nonsense":        {config.EnvShutdownGrace: "soon"},
		"sentry dsn is not a url":  {config.EnvSentryDSN: "not a dsn"},
		"csrf key is not hex":      {config.EnvCSRFKey: "not-hex-at-all"},
		"csrf key is wrong length": {config.EnvCSRFKey: "abcdef"},
	}

	for name, kv := range cases {
		t.Run(name, func(t *testing.T) {
			t.Parallel()

			c, err := config.Load(env(kv))
			if err == nil {
				t.Fatalf("wanted a startup failure, got a Config: %+v", c)
			}

			if !errors.Is(err, config.ErrInvalidConfig) {
				t.Errorf("error does not wrap ErrInvalidConfig: %v", err)
			}

			if c != nil {
				t.Error("a failed load must return no Config at all")
			}
		})
	}
}

// TestSecretsAreNotEchoed: a rejected CSRF key must not appear in the
// error, because errors are logged and a log is not a place to put a
// key.
func TestSecretsAreNotEchoed(t *testing.T) {
	t.Parallel()

	const secret = "00112233445566778899aabbccdd" // valid hex, wrong length

	_, err := config.Load(env(map[string]string{config.EnvCSRFKey: secret}))
	if err == nil {
		t.Fatal("wanted a failure for a short CSRF key")
	}

	if strings.Contains(err.Error(), secret) {
		t.Errorf("the rejected key was echoed in the error: %v", err)
	}
}

// TestHalfSetMetricsAuthAborts covers the case the issue calls out
// explicitly: auth config that is half-set must fail loudly, in both
// directions.
func TestHalfSetMetricsAuthAborts(t *testing.T) {
	t.Parallel()

	cases := map[string]map[string]string{
		"user without password": {config.EnvMetricsUser: testUser},
		"password without user": {config.EnvMetricsPassword: testPass},
	}

	for name, kv := range cases {
		t.Run(name, func(t *testing.T) {
			t.Parallel()

			_, err := config.Load(env(kv))
			if err == nil {
				t.Fatal("half-set metrics credentials must abort startup")
			}

			if !errors.Is(err, config.ErrInvalidConfig) {
				t.Errorf("error does not wrap ErrInvalidConfig: %v", err)
			}
		})
	}

	both, err := config.Load(env(map[string]string{
		config.EnvMetricsUser: testUser, config.EnvMetricsPassword: testPass,
	}))
	if err != nil {
		t.Fatalf("both credentials set must be valid, got: %v", err)
	}

	if both.MetricsUser != testUser || both.MetricsPassword != testPass {
		t.Error("credentials did not survive parsing")
	}

	neither, err := config.Load(env(nil))
	if err != nil {
		t.Fatalf("neither credential set must be valid, got: %v", err)
	}

	if neither.MetricsUser != "" || neither.MetricsPassword != "" {
		t.Error("credentials appeared from nowhere")
	}
}

// TestEveryFailureIsReported: one restart should surface the whole list,
// not just the first problem.
func TestEveryFailureIsReported(t *testing.T) {
	t.Parallel()

	_, err := config.Load(env(map[string]string{
		config.EnvPort:           "eighty",
		config.EnvDebug:          "yes",
		config.EnvRequestTimeout: "soon",
	}))
	if err == nil {
		t.Fatal("wanted failures")
	}

	for _, key := range []string{
		config.EnvPort, config.EnvDebug, config.EnvRequestTimeout,
	} {
		if !strings.Contains(err.Error(), key) {
			t.Errorf("%s is broken but is not named in the error: %v", key, err)
		}
	}
}

// TestValidValuesAreUsed proves the parsers accept what they document.
func TestValidValuesAreUsed(t *testing.T) {
	t.Parallel()

	const key = "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef"

	c, err := config.Load(env(map[string]string{
		config.EnvPort:           "9000",
		config.EnvDebug:          "true",
		config.EnvMaxRequestBody: "2MiB",
		config.EnvRequestTimeout: "45s",
		config.EnvShutdownGrace:  "5s",
		config.EnvDataDir:        "/var/lib/example",
		config.EnvCSRFKey:        key,
	}))
	if err != nil {
		t.Fatalf("valid environment was rejected: %v", err)
	}

	if c.Port != 9000 {
		t.Errorf("Port = %d, want 9000", c.Port)
	}

	if c.MaxRequestBody != 2<<20 {
		t.Errorf("MaxRequestBody = %d, want %d", c.MaxRequestBody, 2<<20)
	}

	if c.RequestTimeout != 45*time.Second {
		t.Errorf("RequestTimeout = %s, want 45s", c.RequestTimeout)
	}

	if c.HSTS {
		t.Error("HSTS must default off when DEBUG is true")
	}

	if len(c.CSRFKey) != config.CSRFKeyBytes || c.CSRFKeyEphemeral {
		t.Errorf("CSRFKey not decoded: len=%d ephemeral=%v",
			len(c.CSRFKey), c.CSRFKeyEphemeral)
	}

	if c.DBPath != "/var/lib/example/simplexcalc.db" {
		t.Errorf("DBPath = %q, want it derived from DATA_DIR", c.DBPath)
	}
}

// TestExplicitOverridesDerivedDBPath: DB_PATH wins over the DATA_DIR
// derivation, which is the only reason it exists.
func TestExplicitOverridesDerivedDBPath(t *testing.T) {
	t.Parallel()

	c, err := config.Load(env(map[string]string{
		config.EnvDataDir: "/var/lib/example",
		config.EnvDBPath:  "/srv/other.db",
	}))
	if err != nil {
		t.Fatalf("valid environment was rejected: %v", err)
	}

	if c.DBPath != "/srv/other.db" {
		t.Errorf("DBPath = %q, want /srv/other.db", c.DBPath)
	}
}