package config

import (
	"bytes"
	"encoding/json"
	"log/slog"
	"reflect"
	"strings"
	"testing"
	"time"

	"github.com/spf13/viper"
	"go.yaml.in/yaml/v3"
)

// resetViper isolates tests that touch the global Viper instance.
func resetViper(t *testing.T) {
	t.Helper()
	viper.Reset()
	t.Cleanup(viper.Reset)
}

// captureLogs sends the default slog logger to a buffer until the test ends.
func captureLogs(t *testing.T, level slog.Level) *bytes.Buffer {
	t.Helper()
	var buf bytes.Buffer
	def := slog.Default()
	handler := slog.NewTextHandler(&buf, &slog.HandlerOptions{
		Level: level,
	})
	slog.SetDefault(slog.New(handler))
	t.Cleanup(func() {
		slog.SetDefault(def)
	})
	return &buf
}

func defaultConfig(t *testing.T) JobSearchConfig {
	t.Helper()
	var conf JobSearchConfig
	if err := applyDefaults(&conf); err != nil {
		t.Fatalf("defaults: %v", err)
	}
	return conf
}

func TestDefaults(t *testing.T) {
	conf := defaultConfig(t)
	if conf.Logging.Level != "warn" {
		t.Errorf("Logging.Level = %q; want warn", conf.Logging.Level)
	}
	const apiRoot = "https://www.find-tender.service.gov.uk/api/1.0"
	if conf.Sources.FindATender.APIRoot != apiRoot {
		t.Errorf("FindATender.APIRoot = %q", conf.Sources.FindATender.APIRoot)
	}
	if conf.Sources.FTSMock.APIRoot != "" {
		t.Errorf("FTSMock.APIRoot = %q; want empty", conf.Sources.FTSMock.APIRoot)
	}
	for name, src := range map[string]JSCSourcesSource{
		"find_a_tender": conf.Sources.FindATender.JSCSourcesSource,
		"fts_mock":      conf.Sources.FTSMock.JSCSourcesSource,
		"sleeper":       conf.Sources.Sleeper.JSCSourcesSource,
	} {
		if src.Enabled || src.Interval != 10*time.Minute {
			t.Errorf("%s source = %+v; want disabled, 10m", name, src)
		}
	}
}

func TestLoggingSection(t *testing.T) {
	c := JSCLogging{
		Level: "info",
		File:  "/tmp/x.log",
	}

	if got, want := c.Keys(), []string{
		"level",
		"file",
	}; !reflect.DeepEqual(got, want) {
		t.Errorf("Keys = %v; want %v", got, want)
	}
	if got, want := c.Map(), map[string]any{
		"level": "info",
		"file":  "/tmp/x.log",
	}; !reflect.DeepEqual(got, want) {
		t.Errorf("Map = %v; want %v", got, want)
	}
	if got, want := c.Flatten(), map[string]any{
		"logging.level": "info",
		"logging.file":  "/tmp/x.log",
	}; !reflect.DeepEqual(got, want) {
		t.Errorf("Flatten = %v; want %v", got, want)
	}
	if k, err := c.TypeOf("file"); err != nil || k != reflect.String {
		t.Errorf("TypeOf(file) = %v, %v", k, err)
	}
	if v, err := c.ValueOf("level"); err != nil || v != "info" {
		t.Errorf("ValueOf(level) = %v, %v", v, err)
	}
	if _, err := c.TypeOf("nope"); err == nil {
		t.Error("TypeOf(nope) succeeded")
	}
	if err := c.SetValue("file", "/var/log/js.log"); err != nil ||
		c.File != "/var/log/js.log" {
		t.Errorf("SetValue(file) = %v, File = %q", err, c.File)
	}
}

func TestLoggingLevelValidation(t *testing.T) {
	var c JSCLogging
	for _, lvl := range []string{"debug", "info", "warn", "error"} {
		if err := c.SetValue("level", lvl); err != nil || c.Level != lvl {
			t.Errorf("SetValue(level, %q) = %v, Level = %q", lvl, err, c.Level)
		}
	}
	for _, lvl := range []string{"", "trace", "WARN", "fatal"} {
		if err := c.SetValue("level", lvl); err == nil ||
			!strings.Contains(err.Error(), "invalid log level") {
			t.Errorf("SetValue(level, %q) = %v; want invalid log level", lvl, err)
		}
	}
	if c.Level != "error" {
		t.Errorf("rejected level was stored: %q", c.Level)
	}
	// Validation also applies through the top-level config.
	conf := defaultConfig(t)
	if err := conf.SetValue("logging.level", "loud"); err == nil {
		t.Error("JobSearchConfig.SetValue(logging.level, loud) succeeded")
	}
	// Other keys are not validated.
	if err := c.validate("file", "anything"); err != nil {
		t.Errorf("validate(file) = %v", err)
	}
}

func TestLevelToLogLevel(t *testing.T) {
	tests := map[string]slog.Level{
		"debug": slog.LevelDebug,
		"info":  slog.LevelInfo,
		"warn":  slog.LevelWarn,
		"error": slog.LevelError,
		"":      99,
		"bogus": 99,
	}
	for in, want := range tests {
		if got := LevelToLogLevel(in); got != want {
			t.Errorf("LevelToLogLevel(%q) = %v; want %v", in, got, want)
		}
		c := JSCLogging{
			Level: in,
		}
		if got := c.LogLevel(); got != want {
			t.Errorf("LogLevel() with %q = %v; want %v", in, got, want)
		}
	}
}

func TestSourceSection(t *testing.T) {
	c := JSCSourcesSource{
		Enabled:  true,
		Interval: time.Minute,
	}

	if got, want := c.Keys(), []string{
		"enabled",
		"interval",
	}; !reflect.DeepEqual(got, want) {
		t.Errorf("Keys = %v; want %v", got, want)
	}
	want := map[string]any{"enabled": true, "interval": "1m0s"}
	if got := c.Map(); !reflect.DeepEqual(got, want) {
		t.Errorf("Map = %v; want %v", got, want)
	}
	wantFlat := map[string]any{"enabled": true, "interval": "1m0s"}
	if got := c.Flatten(); !reflect.DeepEqual(got, wantFlat) {
		t.Errorf("Flatten = %v; want %v (no prefix)", got, wantFlat)
	}
	if k, err := c.TypeOf("interval"); err != nil || k != reflect.String {
		t.Errorf("TypeOf(interval) = %v, %v; want String", k, err)
	}
	if k, err := c.TypeOf("enabled"); err != nil || k != reflect.Bool {
		t.Errorf("TypeOf(enabled) = %v, %v; want Bool", k, err)
	}
	if v, err := c.ValueOf("interval"); err != nil || v != "1m0s" {
		t.Errorf("ValueOf(interval) = %v, %v", v, err)
	}
	if err := c.SetValue("interval", "5s"); err != nil ||
		c.Interval != 5*time.Second {
		t.Errorf("SetValue(interval, 5s) = %v, Interval = %v", err, c.Interval)
	}
	if err := c.SetValue("interval", "never"); err == nil {
		t.Error("SetValue(interval, never) succeeded")
	}
}

func TestConcreteSourceSections(t *testing.T) {
	tests := []struct {
		prefix        string
		section       Section
		apiRoot       bool
		blockShutdown bool
	}{
		{JSCKSourceFindATender, &JSCSourceFindATender{}, true, false},
		{JSCKSourceFTSMock, &JSCSourceFTSMock{}, true, false},
		{JSCKSourceSleeper, &JSCSourceSleeper{}, false, true},
	}
	for _, tt := range tests {
		t.Run(tt.prefix, func(t *testing.T) {
			s := tt.section
			// Embedded source fields are promoted.
			if err := s.SetValue("enabled", "true"); err != nil {
				t.Fatalf("SetValue(enabled): %v", err)
			}
			if err := s.SetValue("interval", 2*time.Minute); err != nil {
				t.Fatalf("SetValue(interval): %v", err)
			}
			if v, err := s.ValueOf("enabled"); err != nil || v != true {
				t.Errorf("ValueOf(enabled) = %v, %v", v, err)
			}
			if k, err := s.TypeOf("interval"); err != nil || k != reflect.String {
				t.Errorf("TypeOf(interval) = %v, %v", k, err)
			}

			wantMap := map[string]any{"enabled": true, "interval": "2m0s"}
			wantFlat := map[string]any{
				tt.prefix + ".enabled":  true,
				tt.prefix + ".interval": "2m0s",
			}
			if tt.apiRoot {
				if err := s.SetValue("api_root", "http://localhost:8080"); err != nil {
					t.Fatalf("SetValue(api_root): %v", err)
				}
				if v, err := s.ValueOf("api_root"); err != nil ||
					v != "http://localhost:8080" {
					t.Errorf("ValueOf(api_root) = %v, %v", v, err)
				}
				wantMap["api_root"] = "http://localhost:8080"
				wantFlat[tt.prefix+".api_root"] = "http://localhost:8080"
			} else if _, err := s.TypeOf("api_root"); err == nil {
				t.Error("TypeOf(api_root) succeeded on a source without one")
			}
			if tt.blockShutdown {
				if err := s.SetValue("block_shutdown", "true"); err != nil {
					t.Fatalf("SetValue(block_shutdown): %v", err)
				}
				if k, err := s.TypeOf("block_shutdown"); err != nil ||
					k != reflect.Bool {
					t.Errorf("TypeOf(block_shutdown) = %v, %v", k, err)
				}
				wantMap["block_shutdown"] = true
				wantFlat[tt.prefix+".block_shutdown"] = true
			} else if _, err := s.TypeOf("block_shutdown"); err == nil {
				t.Error("TypeOf(block_shutdown) succeeded on a source without one")
			}

			if got := s.Map(); !reflect.DeepEqual(got, wantMap) {
				t.Errorf("Map = %v; want %v", got, wantMap)
			}
			if got := s.Flatten(); !reflect.DeepEqual(got, wantFlat) {
				t.Errorf("Flatten = %v; want %v", got, wantFlat)
			}
			if _, err := s.ValueOf("nope"); err == nil {
				t.Error("ValueOf(nope) succeeded")
			}
		})
	}
}

func TestSourcesSection(t *testing.T) {
	var c JSCSources
	if err := c.SetValue("fts_mock.api_root", "http://mock"); err != nil {
		t.Fatalf("SetValue: %v", err)
	}
	if c.FTSMock.APIRoot != "http://mock" {
		t.Errorf("FTSMock.APIRoot = %q", c.FTSMock.APIRoot)
	}
	if v, err := c.ValueOf("fts_mock.api_root"); err != nil ||
		v != "http://mock" {
		t.Errorf("ValueOf = %v, %v", v, err)
	}
	if k, err := c.TypeOf("sleeper.enabled"); err != nil || k != reflect.Bool {
		t.Errorf("TypeOf(sleeper.enabled) = %v, %v", k, err)
	}
	if _, err := c.TypeOf("sleeper"); err == nil {
		t.Error("TypeOf(sleeper) succeeded on a section key")
	}

	m := c.Map()
	for _, k := range []string{"find_a_tender", "fts_mock", "sleeper"} {
		if _, ok := m[k].(map[string]any); !ok {
			t.Errorf("Map()[%q] = %#v; want nested map", k, m[k])
		}
	}
	flat := c.Flatten()
	if flat["sources.fts_mock.api_root"] != "http://mock" {
		t.Errorf("Flatten missing sources.fts_mock.api_root: %v", flat)
	}
	if len(flat) != 9 {
		t.Errorf("Flatten has %d keys; want 9: %v", len(flat), flat)
	}
}

func TestJobSearchConfigMap(t *testing.T) {
	conf := defaultConfig(t)
	m := conf.Map()

	logging, ok := m["logging"].(map[string]any)
	if !ok || logging["level"] != "warn" {
		t.Errorf("Map()[logging] = %#v", m["logging"])
	}
	sources, ok := m["sources"].(map[string]any)
	if !ok {
		t.Fatalf("Map()[sources] = %#v", m["sources"])
	}
	fat, ok := sources["find_a_tender"].(map[string]any)
	if !ok || fat["interval"] != "10m0s" {
		t.Errorf("Map()[sources][find_a_tender] = %#v", sources["find_a_tender"])
	}
}

func TestString(t *testing.T) {
	conf := defaultConfig(t)
	s := conf.String()
	for _, want := range []string{
		"logging.level = warn <string>\n",
		"sources.sleeper.enabled = false <bool>\n",
		"sources.find_a_tender.interval = 10m0s <string>\n",
	} {
		if !strings.Contains(s, want) {
			t.Errorf("String() missing %q:\n%s", want, s)
		}
	}
	if n := strings.Count(s, "\n"); n != len(conf.Flatten()) {
		t.Errorf("String() has %d lines; want %d", n, len(conf.Flatten()))
	}
}

// JSON and YAML give the configuration as nested sections.
func TestSerialised(t *testing.T) {
	conf := defaultConfig(t)
	tests := []struct {
		name      string
		output    string
		unmarshal func([]byte, any) error
	}{
		{"JSON", conf.JSON(), json.Unmarshal},
		{"YAML", conf.YAML(), yaml.Unmarshal},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			var m map[string]map[string]any
			if err := tt.unmarshal([]byte(tt.output), &m); err != nil {
				t.Fatalf("%s() doesn't parse: %v\n%s", tt.name, err, tt.output)
			}

			if m["logging"]["level"] != "warn" {
				t.Errorf("logging.level = %#v", m["logging"]["level"])
			}
			for _, source := range []string{"fts_mock", "sleeper"} {
				if _, ok := m["sources"][source]; !ok {
					t.Errorf("missing sources.%s: %v", source, m["sources"])
				}
			}
		})
	}
}

// Output of JSON()/YAML() can be read back as a config file.
func TestSerialisedRoundTrip(t *testing.T) {
	orig := defaultConfig(t)
	orig.Logging.Level = "info"
	orig.Sources.FTSMock.Enabled = true
	orig.Sources.FTSMock.APIRoot = "http://mock"
	orig.Server.WebSocket.MaxMessageSize = 64 << 10

	for _, format := range []string{"json", "yaml"} {
		t.Run(format, func(t *testing.T) {
			resetViper(t)
			out := orig.JSON()
			if format == "yaml" {
				out = orig.YAML()
			}

			viper.SetConfigType(format)
			if err := viper.ReadConfig(strings.NewReader(out)); err != nil {
				t.Fatalf("ReadConfig: %v", err)
			}

			var got JobSearchConfig
			LoadFromViper(&got)
			if !reflect.DeepEqual(got, orig) {
				t.Errorf("round trip =\n%+v\nwant\n%+v", got, orig)
			}
		})
	}
}

func TestLoadToViper(t *testing.T) {
	resetViper(t)
	conf := defaultConfig(t)
	LoadToViper(conf)
	for key, want := range conf.Flatten() {
		if got := viper.Get(key); !reflect.DeepEqual(got, want) {
			t.Errorf("viper.Get(%q) = %#v; want %#v", key, got, want)
		}
	}
}

func TestLoadDefaultConfig(t *testing.T) {
	resetViper(t)
	LoadDefaultConfig()
	if got := viper.GetString("logging.level"); got != "warn" {
		t.Errorf("logging.level = %q; want warn", got)
	}
	if got := viper.GetDuration(
		"sources.sleeper.interval",
	); got != 10*time.Minute {
		t.Errorf("sources.sleeper.interval = %v; want 10m", got)
	}
}

func TestLoadFromViper(t *testing.T) {
	resetViper(t)
	LoadDefaultConfig()
	viper.Set("logging.level", "debug")
	viper.Set("logging.file", "/tmp/js.log")
	viper.Set("sources.sleeper.enabled", "true") // string, read as bool
	viper.Set("sources.fts_mock.interval", "30s")
	viper.Set("sources.fts_mock.api_root", "http://mock")
	viper.Set("unknown.key", "ignored")

	var conf JobSearchConfig
	LoadFromViper(&conf)

	want := defaultConfig(t)
	want.Logging.Level = "debug"
	want.Logging.File = "/tmp/js.log"
	want.Sources.Sleeper.Enabled = true
	want.Sources.FTSMock.Interval = 30 * time.Second
	want.Sources.FTSMock.APIRoot = "http://mock"
	if !reflect.DeepEqual(conf, want) {
		t.Errorf("LoadFromViper =\n%+v\nwant\n%+v", conf, want)
	}
}

func TestViperRoundTrip(t *testing.T) {
	resetViper(t)
	orig := defaultConfig(t)
	orig.Logging.Level = "error"
	orig.Sources.FindATender.Enabled = true
	orig.Sources.FindATender.Interval = 45 * time.Second
	LoadToViper(orig)

	var got JobSearchConfig
	LoadFromViper(&got)
	if !reflect.DeepEqual(got, orig) {
		t.Errorf("round trip =\n%+v\nwant\n%+v", got, orig)
	}
}

// Invalid values from Viper are skipped with a warning, leaving the existing
// value.
func TestLoadFromViperInvalidValues(t *testing.T) {
	resetViper(t)
	logs := captureLogs(t, slog.LevelWarn)
	viper.Set("logging.level", "shouty")
	viper.Set("sources.sleeper.interval", "eventually")

	conf := defaultConfig(t)
	LoadFromViper(&conf)
	if conf.Logging.Level != "warn" {
		t.Errorf("Logging.Level = %q; want warn kept", conf.Logging.Level)
	}
	if conf.Sources.Sleeper.Interval != 10*time.Minute {
		t.Errorf(
			"Sleeper.Interval = %v; want 10m kept", conf.Sources.Sleeper.Interval,
		)
	}
	for _, key := range []string{"logging.level", "sources.sleeper.interval"} {
		if !strings.Contains(logs.String(), "key="+key) {
			t.Errorf("no warning logged for %s: %s", key, logs)
		}
	}
}

func TestDatabaseSection(t *testing.T) {
	c := JSCDatabase{
		File: "./jobsearch.db",
	}

	if got, want := c.Keys(), []string{"file"}; !reflect.DeepEqual(got, want) {
		t.Errorf("Keys = %v; want %v", got, want)
	}
	if got, want := c.Map(), map[string]any{
		"file": "./jobsearch.db",
	}; !reflect.DeepEqual(got, want) {
		t.Errorf("Map = %v; want %v", got, want)
	}
	want := map[string]any{"database.file": "./jobsearch.db"}
	if got := c.Flatten(); !reflect.DeepEqual(got, want) {
		t.Errorf("Flatten = %v; want %v", got, want)
	}
	if k, err := c.TypeOf("file"); err != nil || k != reflect.String {
		t.Errorf("TypeOf(file) = %v, %v", k, err)
	}
	if v, err := c.ValueOf("file"); err != nil || v != "./jobsearch.db" {
		t.Errorf("ValueOf(file) = %v, %v", v, err)
	}
	if _, err := c.TypeOf("nope"); err == nil {
		t.Error("TypeOf(nope) succeeded")
	}
	if _, err := c.ValueOf("nope"); err == nil {
		t.Error("ValueOf(nope) succeeded")
	}
	if err := c.SetValue("file", "/var/lib/js.db"); err != nil ||
		c.File != "/var/lib/js.db" {
		t.Errorf("SetValue(file) = %v, File = %q", err, c.File)
	}
	if err := c.SetValue("file", 42); err == nil {
		t.Error("SetValue(file, 42) succeeded")
	}

	// The root configuration reaches it as database.file.
	conf := defaultConfig(t)
	if err := conf.SetValue("database.file", "./other.db"); err != nil ||
		conf.Database.File != "./other.db" {
		t.Errorf("SetValue(database.file) = %v, File = %q", err, conf.Database.File)
	}
}

func TestViperValue(t *testing.T) {
	resetViper(t)
	viper.Set("s", "text")
	viper.Set("i", "42") // strings are converted
	viper.Set("b", "true")
	viper.Set("env_list", "a, b")           // e.g. from an environment variable
	viper.Set("file_list", []any{"a", "b"}) // e.g. from a YAML list

	for _, tt := range []struct {
		key  string
		kind reflect.Kind
		want any
	}{
		{"s", reflect.String, "text"},
		{"i", reflect.Int, 42},
		{"b", reflect.Bool, true},
		{"env_list", reflect.Slice, "a, b"}, // split by SetValue
		{"file_list", reflect.Slice, []string{"a", "b"}},
	} {
		got, ok := viperValue(tt.key, tt.kind)
		if !ok || !reflect.DeepEqual(got, tt.want) {
			t.Errorf(
				"viperValue(%q, %v) = %#v, %v; want %#v",
				tt.key,
				tt.kind,
				got,
				ok,
				tt.want,
			)
		}
	}
	unhandled := []reflect.Kind{reflect.Float64, reflect.Int8, reflect.Map}
	for _, kind := range unhandled {
		if got, ok := viperValue("i", kind); ok {
			t.Errorf("viperValue(i, %v) = %#v, true; want unhandled", kind, got)
		}
	}
}

// max_message_size can't be -1 (no limit), directly or through the whole
// configuration; 0 (the default) and explicit sizes are accepted.
func TestWebSocketMaxMessageSizeNoLimit(t *testing.T) {
	var c JSCServerWebSocket
	if err := c.SetValue("max_message_size", "-1"); err == nil ||
		!strings.Contains(err.Error(), "can't be -1") {
		t.Errorf("SetValue(max_message_size, -1) = %v; want rejected", err)
	}
	if c.MaxMessageSize != 0 {
		t.Errorf("rejected size was stored: %v", c.MaxMessageSize)
	}

	for _, text := range []string{"0B", "64KiB"} {
		if err := c.SetValue("max_message_size", text); err != nil {
			t.Errorf("SetValue(max_message_size, %s): %v", text, err)
		}
	}

	conf := defaultConfig(t)
	if err := conf.SetValue(
		"server.websocket.max_message_size", "-1",
	); err == nil {
		t.Error(
			"JobSearchConfig.SetValue(server.websocket.max_message_size, -1) succeeded",
		)
	}
}

// A source's interval must be greater than 0, through the embedded section's
// promoted validate; a source is turned off with enabled.
func TestSourceIntervalMustBePositive(t *testing.T) {
	conf := defaultConfig(t)
	for _, key := range []string{
		"sources.find_a_tender.interval",
		"sources.fts_mock.interval",
		"sources.sleeper.interval",
	} {
		for _, value := range []string{"0s", "-1m"} {
			err := conf.SetValue(key, value)
			if err == nil || !strings.Contains(err.Error(), "greater than 0") {
				t.Errorf("SetValue(%s, %s) = %v; want rejected", key, value, err)
			}
		}
		if err := conf.SetValue(key, "1m"); err != nil {
			t.Errorf("SetValue(%s, 1m): %v", key, err)
		}
	}
	if conf.Sources.FindATender.Interval.Minutes() != 1 {
		t.Errorf(
			"FindATender.Interval = %v; want 1m", conf.Sources.FindATender.Interval,
		)
	}
}