// Package manualsync synchronizes measurement manual-mode changes with the
// protocol service responsible for the measurement's data source
package manualsync

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"math"
	"net/http"
	"net/url"
	"strconv"
	"strings"

	"modelRT/config"
	"modelRT/constants"
	"modelRT/orm"
)

const maxErrorResponseBody = 4 << 10

// SyntheticData is one manually supplied measurement value
type SyntheticData struct {
	Time  int64   `json:"time"`
	Value float64 `json:"value"`
}

// Target identifies a measurement in a downstream protocol service
type Target struct {
	Type    int    `json:"type"`
	Station string `json:"station"`
	MainPos string `json:"main_pos"`
	SubPos  string `json:"sub_pos"`
	Option  string `json:"option"`
}

// Request is the payload accepted by POST /api/manual
type Request struct {
	Mode   int16           `json:"mode"`
	Data   []SyntheticData `json:"data,omitempty"`
	Target Target          `json:"target"`
}

// Syncer synchronizes a measurement mode or manual-value change
type Syncer interface {
	Sync(context.Context, orm.JSONMap, int16, *SyntheticData) error
}

// Client calls the protocol-specific manual synchronization endpoint
type Client struct {
	httpClient        *http.Client
	protocolCL3611URL string
	protocol104URL    string
}

// NewClient validates the configuration and constructs a reusable client
func NewClient(cfg config.ManualSyncConfig) (*Client, error) {
	if cfg.Timeout <= 0 {
		return nil, fmt.Errorf("manual sync timeout must be greater than zero")
	}
	protocolCL3611URL, err := endpointURL(cfg.ProtocolCL3611URL, cfg.APIPath)
	if err != nil {
		return nil, fmt.Errorf("invalid protocol CL3611 URL: %w", err)
	}
	protocol104URL, err := endpointURL(cfg.Protocol104URL, cfg.APIPath)
	if err != nil {
		return nil, fmt.Errorf("invalid protocol 104 URL: %w", err)
	}

	return &Client{
		httpClient:        &http.Client{Timeout: cfg.Timeout},
		protocolCL3611URL: protocolCL3611URL,
		protocol104URL:    protocol104URL,
	}, nil
}

// Sync posts one mode transition or manual-value update. Data is omitted for
// mode transitions and included only when sample is non-nil in manual mode
func (c *Client) Sync(ctx context.Context, dataSource orm.JSONMap, mode int16, data *SyntheticData) error {
	if c == nil || c.httpClient == nil {
		return fmt.Errorf("manual sync client is not initialized")
	}
	if mode != constants.MeasurementModeManual && mode != constants.MeasurementModeAutomatic {
		return fmt.Errorf("manual sync mode must be 0 or 1, got %d", mode)
	}
	if mode == constants.MeasurementModeAutomatic && data != nil {
		return fmt.Errorf("automatic mode manual sync request cannot contain data")
	}

	endpoint, target, err := c.resolveTarget(dataSource)
	if err != nil {
		return err
	}
	requestPayload := Request{Mode: mode, Target: target}
	if data != nil {
		requestPayload.Data = []SyntheticData{*data}
	}
	body, err := json.Marshal(requestPayload)
	if err != nil {
		return fmt.Errorf("encode manual sync request: %w", err)
	}

	request, err := http.NewRequestWithContext(ctx, http.MethodPost, endpoint, bytes.NewReader(body))
	if err != nil {
		return fmt.Errorf("create manual sync request: %w", err)
	}
	request.Header.Set("Content-Type", "application/json")

	response, err := c.httpClient.Do(request)
	if err != nil {
		return fmt.Errorf("call manual sync endpoint: %w", err)
	}
	defer response.Body.Close()
	if response.StatusCode >= http.StatusOK && response.StatusCode < http.StatusMultipleChoices {
		_, _ = io.Copy(io.Discard, response.Body)
		return nil
	}

	responseBody, readErr := io.ReadAll(io.LimitReader(response.Body, maxErrorResponseBody))
	if readErr != nil {
		return fmt.Errorf("manual sync endpoint returned %s and response body could not be read: %w", response.Status, readErr)
	}
	message := strings.TrimSpace(string(responseBody))
	if message == "" {
		return fmt.Errorf("manual sync endpoint returned %s", response.Status)
	}
	return fmt.Errorf("manual sync endpoint returned %s: %s", response.Status, message)
}

type rawDataSource struct {
	Type      int          `json:"type"`
	IOAddress rawIOAddress `json:"io_address"`
}

type rawIOAddress struct {
	DType   int    `json:"dtype"`
	Station string `json:"station"`
	Device  string `json:"device"`
	Channel string `json:"channel"`
	Option  string `json:"option"`
	Packet  any    `json:"packet"`
	Offset  any    `json:"offset"`
}

func (c *Client) resolveTarget(dataSource orm.JSONMap) (string, Target, error) {
	if dataSource == nil {
		return "", Target{}, fmt.Errorf("measurement data_source is null")
	}
	encoded, err := json.Marshal(dataSource)
	if err != nil {
		return "", Target{}, fmt.Errorf("encode measurement data_source: %w", err)
	}
	var source rawDataSource
	if err := json.Unmarshal(encoded, &source); err != nil {
		return "", Target{}, fmt.Errorf("decode measurement data_source: %w", err)
	}
	station := strings.TrimSpace(source.IOAddress.Station)
	if station == "" {
		return "", Target{}, fmt.Errorf("measurement data_source io_address.station is required")
	}

	switch source.Type {
	case 1:
		device := strings.TrimSpace(source.IOAddress.Device)
		channel := strings.TrimSpace(source.IOAddress.Channel)
		if device == "" {
			return "", Target{}, fmt.Errorf("CL3611 data_source io_address.device is required")
		}
		if channel == "" {
			return "", Target{}, fmt.Errorf("CL3611 data_source io_address.channel is required")
		}
		target := Target{
			Station: station,
			MainPos: device,
			SubPos:  channel,
		}
		switch source.IOAddress.DType {
		case 1:
			target.Type = 1
			target.Option = strings.TrimSpace(source.IOAddress.Option)
		case 2:
			target.Type = 2
		default:
			return "", Target{}, fmt.Errorf("CL3611 data_source dtype must be 1 or 2, got %d", source.IOAddress.DType)
		}
		return c.protocolCL3611URL, target, nil
	case 2:
		packet, err := integerString(source.IOAddress.Packet)
		if err != nil {
			return "", Target{}, fmt.Errorf("104 data_source io_address.packet: %w", err)
		}
		offset, err := integerString(source.IOAddress.Offset)
		if err != nil {
			return "", Target{}, fmt.Errorf("104 data_source io_address.offset: %w", err)
		}
		return c.protocol104URL, Target{
			Type:    3,
			Station: station,
			MainPos: packet,
			SubPos:  offset,
			Option:  "",
		}, nil
	default:
		return "", Target{}, fmt.Errorf("unsupported measurement data_source type %d", source.Type)
	}
}

func endpointURL(baseURL, apiPath string) (string, error) {
	baseURL = strings.TrimSpace(baseURL)
	if baseURL == "" {
		return "", fmt.Errorf("base URL is required")
	}
	apiPath = strings.TrimSpace(apiPath)
	if apiPath == "" {
		return "", fmt.Errorf("API path is required")
	}
	endpoint := strings.TrimRight(baseURL, "/") + "/" + strings.TrimLeft(apiPath, "/")
	parsed, err := url.Parse(endpoint)
	if err != nil {
		return "", err
	}
	if parsed.Scheme != "http" && parsed.Scheme != "https" {
		return "", fmt.Errorf("URL scheme must be http or https")
	}
	if parsed.Host == "" {
		return "", fmt.Errorf("URL host is required")
	}
	return parsed.String(), nil
}

func integerString(value any) (string, error) {
	switch typed := value.(type) {
	case nil:
		return "", fmt.Errorf("is required")
	case float64:
		if math.IsNaN(typed) || math.IsInf(typed, 0) || math.Trunc(typed) != typed {
			return "", fmt.Errorf("must be an integer")
		}
		return strconv.FormatInt(int64(typed), 10), nil
	case string:
		trimmed := strings.TrimSpace(typed)
		if trimmed == "" {
			return "", fmt.Errorf("is required")
		}
		integer, err := strconv.ParseInt(trimmed, 10, 64)
		if err != nil {
			return "", fmt.Errorf("must be an integer: %w", err)
		}
		return strconv.FormatInt(integer, 10), nil
	default:
		return "", fmt.Errorf("has unsupported type %T", value)
	}
}