package gamemaster

import (
	"os"
	"path/filepath"
	"runtime"
	"testing"

	"github.com/stretchr/testify/require"
	"gopkg.in/yaml.v3"
)

type runtimeEventPayloadExpectation struct {
	schemaName    string
	eventTypeConst string
	required       []string
}

var expectedRuntimeEventPayloads = []runtimeEventPayloadExpectation{
	{
		schemaName:     "RuntimeSnapshotUpdatePayload",
		eventTypeConst: "runtime_snapshot_update",
		required: []string{
			"event_type",
			"game_id",
			"current_turn",
			"runtime_status",
			"engine_health_summary",
			"player_turn_stats",
			"occurred_at_ms",
		},
	},
	{
		schemaName:     "GameFinishedPayload",
		eventTypeConst: "game_finished",
		required: []string{
			"event_type",
			"game_id",
			"final_turn_number",
			"runtime_status",
			"player_turn_stats",
			"finished_at_ms",
		},
	},
}

var expectedRuntimeStatusEnum = []string{
	"starting",
	"running",
	"generation_in_progress",
	"generation_failed",
	"stopped",
	"engine_unreachable",
	"finished",
}

// TestRuntimeEventsAsyncAPISpecLoads verifies the spec parses as YAML and is
// pinned to AsyncAPI 3.1.0.
func TestRuntimeEventsAsyncAPISpecLoads(t *testing.T) {
	t.Parallel()

	doc := loadAsyncAPISpec(t)
	require.Equal(t, "3.1.0", getStringValue(t, doc, "asyncapi"))
}

// TestRuntimeEventsAsyncAPIChannel verifies the single channel address and
// the two message references attached to it.
func TestRuntimeEventsAsyncAPIChannel(t *testing.T) {
	t.Parallel()

	doc := loadAsyncAPISpec(t)
	channel := getMapValue(t, doc, "channels", "lobbyEvents")

	require.Equal(t, "gm:lobby_events", getStringValue(t, channel, "address"))

	channelMessages := getMapValue(t, channel, "messages")
	require.ElementsMatch(t,
		[]string{"runtimeSnapshotUpdate", "gameFinished"},
		mapKeys(channelMessages))

	require.Equal(t,
		"#/components/messages/RuntimeSnapshotUpdate",
		getStringValue(t, getMapValue(t, channelMessages, "runtimeSnapshotUpdate"), "$ref"))
	require.Equal(t,
		"#/components/messages/GameFinished",
		getStringValue(t, getMapValue(t, channelMessages, "gameFinished"), "$ref"))
}

// TestRuntimeEventsAsyncAPIOperations verifies that each message has its own
// `send` operation with the correct channel and message reference. Game
// Master is the publisher; no `receive` operations exist on this stream.
func TestRuntimeEventsAsyncAPIOperations(t *testing.T) {
	t.Parallel()

	doc := loadAsyncAPISpec(t)
	operations := getMapValue(t, doc, "operations")

	require.ElementsMatch(t,
		[]string{"publishRuntimeSnapshotUpdate", "publishGameFinished"},
		mapKeys(operations))

	cases := []struct {
		operationName string
		messageKey    string
	}{
		{"publishRuntimeSnapshotUpdate", "runtimeSnapshotUpdate"},
		{"publishGameFinished", "gameFinished"},
	}

	for _, tc := range cases {
		tc := tc
		t.Run(tc.operationName, func(t *testing.T) {
			t.Parallel()

			op := getMapValue(t, operations, tc.operationName)
			require.Equal(t, "send", getStringValue(t, op, "action"))
			require.Equal(t, "#/channels/lobbyEvents",
				getStringValue(t, getMapValue(t, op, "channel"), "$ref"))

			messageRefs := getSliceValue(t, op, "messages")
			require.Len(t, messageRefs, 1, "%s must reference exactly one message", tc.operationName)

			ref, ok := messageRefs[0].(map[string]any)
			require.True(t, ok, "%s message reference must be a map", tc.operationName)
			require.Equal(t,
				"#/channels/lobbyEvents/messages/"+tc.messageKey,
				getStringValue(t, ref, "$ref"))
		})
	}
}

// TestRuntimeEventsAsyncAPIMessageNames verifies that components.messages
// contains exactly the two message names frozen by Stage 06.
func TestRuntimeEventsAsyncAPIMessageNames(t *testing.T) {
	t.Parallel()

	doc := loadAsyncAPISpec(t)
	messages := getMapValue(t, doc, "components", "messages")

	require.ElementsMatch(t,
		[]string{"RuntimeSnapshotUpdate", "GameFinished"},
		mapKeys(messages))

	for _, name := range []string{"RuntimeSnapshotUpdate", "GameFinished"} {
		message := getMapValue(t, messages, name)
		require.Equal(t, name, getStringValue(t, message, "name"),
			"message %s must declare its own name", name)
		require.Equal(t,
			"#/components/schemas/"+name+"Payload",
			getStringValue(t, getMapValue(t, message, "payload"), "$ref"),
			"message %s must reference its payload schema", name)
	}
}

// TestRuntimeEventsAsyncAPIPayloadFreeze verifies that each payload schema
// has the expected required-field set, the correct `event_type` const, and
// `additionalProperties: false`.
func TestRuntimeEventsAsyncAPIPayloadFreeze(t *testing.T) {
	t.Parallel()

	doc := loadAsyncAPISpec(t)
	schemas := getMapValue(t, doc, "components", "schemas")

	for _, expectation := range expectedRuntimeEventPayloads {
		expectation := expectation
		t.Run(expectation.schemaName, func(t *testing.T) {
			t.Parallel()

			payload := getMapValue(t, schemas, expectation.schemaName)

			require.Equal(t, false, getScalarValue(t, payload, "additionalProperties"),
				"%s must reject unknown fields", expectation.schemaName)

			require.ElementsMatch(t,
				toAnySlice(expectation.required),
				getSliceValue(t, payload, "required"),
				"%s required field set", expectation.schemaName)

			properties := getMapValue(t, payload, "properties")

			eventType := getMapValue(t, properties, "event_type")
			require.Equal(t, "string", getStringValue(t, eventType, "type"))
			require.Equal(t, expectation.eventTypeConst,
				getScalarValue(t, eventType, "const"),
				"%s.event_type const must be %q", expectation.schemaName, expectation.eventTypeConst)

			runtimeStatus := getMapValue(t, properties, "runtime_status")
			require.Equal(t, "#/components/schemas/RuntimeStatus",
				getStringValue(t, runtimeStatus, "$ref"),
				"%s.runtime_status must reference RuntimeStatus", expectation.schemaName)

			playerTurnStats := getMapValue(t, properties, "player_turn_stats")
			require.Equal(t, "array", getStringValue(t, playerTurnStats, "type"))
			require.Equal(t, "#/components/schemas/PlayerTurnStat",
				getStringValue(t, getMapValue(t, playerTurnStats, "items"), "$ref"),
				"%s.player_turn_stats items must reference PlayerTurnStat", expectation.schemaName)
		})
	}
}

// TestRuntimeEventsAsyncAPIPlayerTurnStat verifies the per-player stat
// schema shape from gamemaster/README.md §Async Stream Contracts.
func TestRuntimeEventsAsyncAPIPlayerTurnStat(t *testing.T) {
	t.Parallel()

	doc := loadAsyncAPISpec(t)
	stat := getMapValue(t, doc, "components", "schemas", "PlayerTurnStat")

	require.Equal(t, false, getScalarValue(t, stat, "additionalProperties"))
	require.ElementsMatch(t,
		[]any{"user_id", "planets", "population"},
		getSliceValue(t, stat, "required"))

	properties := getMapValue(t, stat, "properties")
	require.Equal(t, "string", getStringValue(t, getMapValue(t, properties, "user_id"), "type"))
	require.Equal(t, "integer", getStringValue(t, getMapValue(t, properties, "planets"), "type"))
	require.Equal(t, "integer", getStringValue(t, getMapValue(t, properties, "population"), "type"))
}

// TestRuntimeEventsAsyncAPIRuntimeStatusEnum verifies the RuntimeStatus
// enum copied locally for the AsyncAPI surface contains the same seven
// values as the OpenAPI surface.
func TestRuntimeEventsAsyncAPIRuntimeStatusEnum(t *testing.T) {
	t.Parallel()

	doc := loadAsyncAPISpec(t)
	schema := getMapValue(t, doc, "components", "schemas", "RuntimeStatus")

	require.ElementsMatch(t, expectedRuntimeStatusEnum, getStringSlice(t, schema, "enum"))
}

func loadAsyncAPISpec(t *testing.T) map[string]any {
	t.Helper()

	payload := loadTextFile(t, filepath.Join("api", "runtime-events-asyncapi.yaml"))

	var doc map[string]any
	if err := yaml.Unmarshal([]byte(payload), &doc); err != nil {
		require.Failf(t, "test failed", "decode spec: %v", err)
	}

	return doc
}

func loadTextFile(t *testing.T, relativePath string) string {
	t.Helper()

	path := filepath.Join(moduleRoot(t), relativePath)
	payload, err := os.ReadFile(path)
	if err != nil {
		require.Failf(t, "test failed", "read file %s: %v", path, err)
	}

	return string(payload)
}

func moduleRoot(t *testing.T) string {
	t.Helper()

	_, thisFile, _, ok := runtime.Caller(0)
	if !ok {
		require.FailNow(t, "runtime.Caller failed")
	}

	return filepath.Dir(thisFile)
}

func getMapValue(t *testing.T, value map[string]any, path ...string) map[string]any {
	t.Helper()

	current := value
	for _, segment := range path {
		raw, ok := current[segment]
		if !ok {
			require.Failf(t, "test failed", "missing map key %s", segment)
		}
		next, ok := raw.(map[string]any)
		if !ok {
			require.Failf(t, "test failed", "value at %s is not a map", segment)
		}
		current = next
	}

	return current
}

func getStringValue(t *testing.T, value map[string]any, key string) string {
	t.Helper()

	raw, ok := value[key]
	if !ok {
		require.Failf(t, "test failed", "missing key %s", key)
	}
	result, ok := raw.(string)
	if !ok {
		require.Failf(t, "test failed", "value at %s is not a string", key)
	}

	return result
}

func getStringSlice(t *testing.T, value map[string]any, key string) []string {
	t.Helper()

	raw := getSliceValue(t, value, key)
	result := make([]string, 0, len(raw))
	for _, item := range raw {
		text, ok := item.(string)
		if !ok {
			require.Failf(t, "test failed", "value at %s is not a string slice", key)
		}
		result = append(result, text)
	}

	return result
}

func getScalarValue(t *testing.T, value map[string]any, key string) any {
	t.Helper()

	raw, ok := value[key]
	if !ok {
		require.Failf(t, "test failed", "missing key %s", key)
	}

	return raw
}

func getSliceValue(t *testing.T, value map[string]any, key string) []any {
	t.Helper()

	raw, ok := value[key]
	if !ok {
		require.Failf(t, "test failed", "missing key %s", key)
	}
	result, ok := raw.([]any)
	if !ok {
		require.Failf(t, "test failed", "value at %s is not a slice", key)
	}

	return result
}

func mapKeys(value map[string]any) []string {
	keys := make([]string, 0, len(value))
	for key := range value {
		keys = append(keys, key)
	}

	return keys
}

func toAnySlice(values []string) []any {
	result := make([]any, 0, len(values))
	for _, value := range values {
		result = append(result, value)
	}

	return result
}