package httpapi

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"strings"
	"unicode/utf8"

	"data-terminal-cloud/internal/device"
	"data-terminal-cloud/internal/deviceauth"
	"data-terminal-cloud/internal/idempotency"
)

type DeviceTelemetrySubmitter interface {
	Submit(context.Context, deviceauth.Identity, string, []byte, device.TelemetryBatchInput) (device.TelemetryBatchResponse, bool, error)
}

func SubmitDeviceTelemetryHandler(service DeviceTelemetrySubmitter) http.Handler {
	return http.HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
		identity, ok := deviceauth.FromContext(request.Context())
		if !ok {
			WriteError(writer, request, http.StatusUnauthorized, "DEVICE_AUTHENTICATION_FAILED", "设备身份验证失败")
			return
		}
		idempotencyKey := strings.TrimSpace(request.Header.Get("Idempotency-Key"))
		if len(idempotencyKey) < 16 || len(idempotencyKey) > 128 {
			WriteAPIError(writer, request, http.StatusBadRequest, Error{
				Code: "VALIDATION_FAILED", Message: "缺少有效的重复请求识别码",
				FieldErrors: []FieldError{{Field: "Idempotency-Key", Message: "长度必须为16至128字符"}},
			})
			return
		}
		rawBody, err := io.ReadAll(request.Body)
		if err != nil {
			WriteError(writer, request, http.StatusBadRequest, "INVALID_REQUEST_BODY", "请求正文无法读取")
			return
		}
		decoder := json.NewDecoder(bytes.NewReader(rawBody))
		decoder.DisallowUnknownFields()
		var input device.TelemetryBatchInput
		if err := decoder.Decode(&input); err != nil || ensureJSONEOF(decoder) != nil {
			WriteAPIError(writer, request, http.StatusBadRequest, Error{
				Code: "VALIDATION_FAILED", Message: "设备遥测参数不正确",
				FieldErrors: []FieldError{{Field: "body", Message: "必须是符合契约的JSON对象"}},
			})
			return
		}
		if fieldErrors := validateTelemetryBatch(input); len(fieldErrors) > 0 {
			WriteAPIError(writer, request, http.StatusBadRequest, Error{Code: "VALIDATION_FAILED", Message: "设备遥测参数不正确", FieldErrors: fieldErrors})
			return
		}
		response, replayed, err := service.Submit(request.Context(), identity, idempotencyKey, rawBody, input)
		if err != nil {
			writeTelemetryError(writer, request, err)
			return
		}
		if replayed {
			writer.Header().Set("Idempotency-Replayed", "true")
		}
		WriteJSON(writer, request, http.StatusOK, response)
	})
}

func validateTelemetryBatch(input device.TelemetryBatchInput) []FieldError {
	fieldErrors := make([]FieldError, 0)
	if len(input.Events) < 1 || len(input.Events) > 500 {
		return append(fieldErrors, FieldError{Field: "events", Message: "必须包含1至500条遥测事件"})
	}
	eventKeys := make(map[string]struct{}, len(input.Events))
	sequences := make(map[int64]struct{}, len(input.Events))
	for index, event := range input.Events {
		prefix := fmt.Sprintf("events[%d]", index)
		eventKey := strings.TrimSpace(event.EventKey)
		if eventKey == "" || utf8.RuneCountInString(eventKey) > 255 || !isSafeErrorCode(eventKey) {
			fieldErrors = append(fieldErrors, FieldError{Field: prefix + ".event_key", Message: "必须是最长255字符的安全业务键"})
		} else if _, exists := eventKeys[eventKey]; exists {
			fieldErrors = append(fieldErrors, FieldError{Field: prefix + ".event_key", Message: "请求内不能重复"})
		} else {
			eventKeys[eventKey] = struct{}{}
		}
		if event.SequenceNo < 1 {
			fieldErrors = append(fieldErrors, FieldError{Field: prefix + ".sequence_no", Message: "必须大于0"})
		} else if _, exists := sequences[event.SequenceNo]; exists {
			fieldErrors = append(fieldErrors, FieldError{Field: prefix + ".sequence_no", Message: "请求内不能重复"})
		} else {
			sequences[event.SequenceNo] = struct{}{}
		}
		if event.OccurredAt.IsZero() {
			fieldErrors = append(fieldErrors, FieldError{Field: prefix + ".occurred_at", Message: "必须是RFC3339时间"})
		}
		if event.ConversationID != "" && !validUUID(event.ConversationID) {
			fieldErrors = append(fieldErrors, FieldError{Field: prefix + ".conversation_id", Message: "必须是UUID"})
		}
		switch event.EventType {
		case "status":
			if event.Status == nil || event.Error != nil || event.CommandResult != nil {
				fieldErrors = append(fieldErrors, FieldError{Field: prefix, Message: "status事件必须且只能包含status对象"})
				continue
			}
			if strings.TrimSpace(event.Status.FirmwareVersion) == "" || utf8.RuneCountInString(event.Status.FirmwareVersion) > 80 {
				fieldErrors = append(fieldErrors, FieldError{Field: prefix + ".status.firmware_version", Message: "不能为空且最长80字符"})
			}
			if event.Status.ReportedConfigRevision < 1 {
				fieldErrors = append(fieldErrors, FieldError{Field: prefix + ".status.reported_config_revision", Message: "必须大于0"})
			}
			if strings.TrimSpace(event.Status.Network.Type) == "" || utf8.RuneCountInString(event.Status.Network.Type) > 40 {
				fieldErrors = append(fieldErrors, FieldError{Field: prefix + ".status.network.type", Message: "不能为空且最长40字符"})
			}
			if event.Status.Network.RSSI != nil && (*event.Status.Network.RSSI < -127 || *event.Status.Network.RSSI > 0) {
				fieldErrors = append(fieldErrors, FieldError{Field: prefix + ".status.network.rssi", Message: "必须为-127至0"})
			}
			if event.Status.RecordingQueue.PendingSegments < 0 || event.Status.RecordingQueue.FailedSegments < 0 {
				fieldErrors = append(fieldErrors, FieldError{Field: prefix + ".status.recording_queue", Message: "分片数量不能为负数"})
			}
			if utf8.RuneCountInString(event.Status.RecordingQueue.LastFailureCode) > 80 || !isSafeErrorCode(event.Status.RecordingQueue.LastFailureCode) {
				fieldErrors = append(fieldErrors, FieldError{Field: prefix + ".status.recording_queue.last_failure_code", Message: "只能是最长80字符的错误码"})
			}
			if event.Status.RecordingQueue.LastFailureAt != nil && event.Status.RecordingQueue.LastFailureAt.IsZero() {
				fieldErrors = append(fieldErrors, FieldError{Field: prefix + ".status.recording_queue.last_failure_at", Message: "必须是RFC3339时间"})
			}
			if event.Status.ConversationStatus != "" && !oneOf(event.Status.ConversationStatus, "PREPARING", "ROOM_ISSUED", "STARTING_AGENT", "ACTIVE", "STOPPING", "COMPLETED", "FAILED", "EXPIRED") {
				fieldErrors = append(fieldErrors, FieldError{Field: prefix + ".status.conversation_status", Message: "不是有效的通话状态"})
			}
		case "error":
			if event.Error == nil || event.Status != nil || event.CommandResult != nil {
				fieldErrors = append(fieldErrors, FieldError{Field: prefix, Message: "error事件必须且只能包含error对象"})
				continue
			}
			if event.Error.Code == "" || utf8.RuneCountInString(event.Error.Code) > 80 || !isSafeErrorCode(event.Error.Code) {
				fieldErrors = append(fieldErrors, FieldError{Field: prefix + ".error.code", Message: "必须是最长80字符的错误码"})
			}
			if !oneOf(event.Error.Severity, "warning", "error", "critical") {
				fieldErrors = append(fieldErrors, FieldError{Field: prefix + ".error.severity", Message: "必须为warning、error或critical"})
			}
		case "command_result":
			if event.CommandResult == nil || event.Status != nil || event.Error != nil {
				fieldErrors = append(fieldErrors, FieldError{Field: prefix, Message: "command_result事件必须且只能包含command_result对象"})
				continue
			}
			if !validUUID(event.CommandResult.CommandID) {
				fieldErrors = append(fieldErrors, FieldError{Field: prefix + ".command_result.command_id", Message: "必须是UUID"})
			}
			if !oneOf(event.CommandResult.Status, "ACKNOWLEDGED", "SUCCEEDED", "FAILED") {
				fieldErrors = append(fieldErrors, FieldError{Field: prefix + ".command_result.status", Message: "必须为ACKNOWLEDGED、SUCCEEDED或FAILED"})
			}
			if event.CommandResult.ResultSummary == nil {
				fieldErrors = append(fieldErrors, FieldError{Field: prefix + ".command_result.result_summary", Message: "必须是JSON对象"})
			} else if path, found := forbiddenDeviceConfigField(event.CommandResult.ResultSummary, prefix+".command_result.result_summary"); found {
				fieldErrors = append(fieldErrors, FieldError{Field: path, Message: "命令结果不得包含密钥、令牌或凭据字段"})
			}
		default:
			fieldErrors = append(fieldErrors, FieldError{Field: prefix + ".event_type", Message: "必须为status、error或command_result"})
		}
	}
	return fieldErrors
}

func writeTelemetryError(writer http.ResponseWriter, request *http.Request, err error) {
	var conflict *device.TelemetryConflictError
	switch {
	case errors.As(err, &conflict):
		WriteAPIError(writer, request, http.StatusConflict, Error{Code: "TELEMETRY_EVENT_CONFLICT", Message: "遥测业务键与已保存事件冲突", Details: map[string]any{"conflicts": conflict.Conflicts}})
	case errors.Is(err, device.ErrTelemetryConfigAhead):
		WriteError(writer, request, http.StatusConflict, "CONFIG_VERSION_CONFLICT", "设备报告的配置版本高于云端期望版本")
	case errors.Is(err, device.ErrTelemetryConversationMissing):
		WriteError(writer, request, http.StatusNotFound, "TELEMETRY_CONVERSATION_NOT_FOUND", "关联通话不存在或不属于当前设备")
	case errors.Is(err, device.ErrTelemetryCommandConflict):
		WriteError(writer, request, http.StatusConflict, "DEVICE_COMMAND_STATE_CONFLICT", "命令不存在、已过期或状态不允许回执")
	case errors.Is(err, idempotency.ErrKeyConflict):
		WriteError(writer, request, http.StatusConflict, "IDEMPOTENCY_KEY_REUSED", "重复请求识别码已用于不同请求")
	case errors.Is(err, idempotency.ErrInProgress):
		WriteAPIError(writer, request, http.StatusConflict, Error{Code: "REQUEST_IN_PROGRESS", Message: "相同请求正在处理中", Retryable: true})
	default:
		WriteAPIError(writer, request, http.StatusServiceUnavailable, Error{Code: "DEVICE_TELEMETRY_UNAVAILABLE", Message: "暂时无法处理设备遥测", Retryable: true})
	}
}