package services

import (
	"fmt"
	"net/url"
	"strings"
	"time"

	"fwh-toolbox-server/domain"
)

// Each document kind owns its content identity version. Bump only the affected
// kind when its query, parsing, or stored content semantics change.
var dataDownloadContentIdentityVersion = map[domain.DataDownloadKind]string{
	domain.DataDownloadPowerFlow:     "v1",
	domain.DataDownloadMqttLog:       "v1",
	domain.DataDownloadEventAlarm:    "v1",
	domain.DataDownloadAlarmSnapshot: "v1",
	domain.DataDownloadEmsLog:        "v1",
	domain.DataDownloadFaultRecord:   "v2",
	domain.DataDownloadUpdateLog:     "v1",
}

type dataDownloadRequestKeyField struct {
	name  string
	value string
}

// buildDataDownloadRequestKey identifies the requested logical document. The
// fields intentionally differ by kind so task-only or irrelevant parameters do
// not reduce reuse between otherwise equivalent requests.
func buildDataDownloadRequestKey(item *domain.DataDownloadItem) (string, error) {
	if item == nil {
		return "", fmt.Errorf("data download item is nil")
	}
	contentVersion, ok := dataDownloadContentIdentityVersion[item.Kind]
	if !ok {
		return "", fmt.Errorf("unsupported data download kind %q", item.Kind)
	}
	if item.SiteSN == "" {
		return "", fmt.Errorf("site SN is required for %s", item.Kind)
	}

	fields := []dataDownloadRequestKeyField{
		{name: "kind", value: string(item.Kind)},
		{name: "content_version", value: contentVersion},
	}
	addSite := func() {
		fields = append(fields, dataDownloadRequestKeyField{name: "site_sn", value: item.SiteSN})
	}
	addDate := func() error {
		if _, err := time.Parse(time.DateOnly, item.Date); err != nil {
			return fmt.Errorf("invalid data date %q for %s", item.Date, item.Kind)
		}
		fields = append(fields, dataDownloadRequestKeyField{name: "date", value: item.Date})
		return nil
	}
	addSubtype := func() error {
		if item.Subtype == "" {
			return fmt.Errorf("subtype is required for %s", item.Kind)
		}
		fields = append(fields, dataDownloadRequestKeyField{name: "subtype", value: item.Subtype})
		return nil
	}
	addTimezone := func() error {
		if item.Timezone == "" {
			return fmt.Errorf("timezone is required for %s", item.Kind)
		}
		fields = append(fields, dataDownloadRequestKeyField{name: "timezone", value: item.Timezone})
		return nil
	}

	switch item.Kind {
	case domain.DataDownloadPowerFlow, domain.DataDownloadEventAlarm, domain.DataDownloadAlarmSnapshot:
		addSite()
		if err := addDate(); err != nil {
			return "", err
		}
		if err := addTimezone(); err != nil {
			return "", err
		}
	case domain.DataDownloadMqttLog:
		addSite()
		if err := addDate(); err != nil {
			return "", err
		}
		if err := addSubtype(); err != nil {
			return "", err
		}
		if err := addTimezone(); err != nil {
			return "", err
		}
	case domain.DataDownloadEmsLog:
		addSite()
		if err := addDate(); err != nil {
			return "", err
		}
		if err := addSubtype(); err != nil {
			return "", err
		}
	case domain.DataDownloadFaultRecord:
		if item.DeviceSN == "" || item.DeviceType == "" {
			return "", fmt.Errorf("device SN and device type are required for %s", item.Kind)
		}
		fields = append(fields,
			dataDownloadRequestKeyField{name: "device_sn", value: item.DeviceSN},
			dataDownloadRequestKeyField{name: "device_type", value: item.DeviceType},
		)
		if err := addDate(); err != nil {
			return "", err
		}
		if err := addTimezone(); err != nil {
			return "", err
		}
	case domain.DataDownloadUpdateLog:
		addSite()
	}

	var key strings.Builder
	key.WriteString("dd-request-v1")
	for _, field := range fields {
		key.WriteByte('|')
		key.WriteString(field.name)
		key.WriteByte('=')
		key.WriteString(url.QueryEscape(field.value))
	}
	return key.String(), nil
}