package opsgenie

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"time"

	"github.com/nicholas-fedor/shoutrrr/pkg/format"
	"github.com/nicholas-fedor/shoutrrr/pkg/services/standard"
	"github.com/nicholas-fedor/shoutrrr/pkg/types"
)

// Service provides OpsGenie as a notification service.
type Service struct {
	standard.Standard

	Config     *Config
	pkr        format.PropKeyResolver
	httpClient types.HTTPClient
}

// alertEndpointTemplate is the OpsGenie API endpoint template for sending alerts.
const (
	alertEndpointTemplate = "https://%s:%d/v2/alerts"
	MaxMessageLength      = 130              // MaxMessageLength is the maximum length of the alert message field in OpsGenie.
	httpSuccessMax        = 299              // httpSuccessMax is the maximum HTTP status code for a successful response.
	defaultHTTPTimeout    = 10 * time.Second // defaultHTTPTimeout is the default timeout for HTTP requests.
)

// ErrUnexpectedStatus indicates that OpsGenie returned an unexpected HTTP status code.
var ErrUnexpectedStatus = errors.New("OpsGenie notification returned unexpected HTTP status code")

// GetID returns the service identifier.
func (s *Service) GetID() string {
	return Scheme
}

// Initialize configures the service with a URL and logger.
func (s *Service) Initialize(serviceURL *url.URL, logger types.StdLogger) error {
	s.SetLogger(logger)
	s.Config = &Config{}
	s.pkr = format.NewPropKeyResolver(s.Config)

	return s.Config.setURL(&s.pkr, serviceURL)
}

// Send delivers a notification message to OpsGenie.
// See: https://docs.opsgenie.com/docs/alert-api#create-alert
func (s *Service) Send(message string, params *types.Params) error {
	config := s.Config
	serviceURL := fmt.Sprintf(
		alertEndpointTemplate,
		config.Host,
		config.Port,
	)

	payload, err := s.newAlertPayload(message, params)
	if err != nil {
		return err
	}

	return s.sendAlert(serviceURL, config.APIKey, &payload)
}

// SetHTTPClient sets a custom HTTP client for the service.
func (s *Service) SetHTTPClient(client types.HTTPClient) {
	s.httpClient = client
}

// newAlertPayload creates a new alert payload for OpsGenie based on the message and parameters.
func (s *Service) newAlertPayload(
	message string,
	params *types.Params,
) (AlertPayload, error) {
	if params == nil {
		params = &types.Params{}
	}

	// Defensive copy
	payloadFields := *s.Config

	if err := s.pkr.UpdateConfigFromParams(&payloadFields, params); err != nil {
		return AlertPayload{}, fmt.Errorf("updating payload fields from params: %w", err)
	}

	// Use `Message` for the title if available, or if the message is too long
	// Use `Description` for the message in these scenarios
	title := payloadFields.Title
	description := message

	if title == "" {
		if len(message) > MaxMessageLength {
			title = message[:MaxMessageLength]
		} else {
			title = message
			description = ""
		}
	}

	if payloadFields.Description != "" && description != "" {
		description += "\n"
	}

	result := AlertPayload{
		Message:     title,
		Alias:       payloadFields.Alias,
		Description: description + payloadFields.Description,
		Responders:  payloadFields.Responders,
		VisibleTo:   payloadFields.VisibleTo,
		Actions:     payloadFields.Actions,
		Tags:        payloadFields.Tags,
		Details:     payloadFields.Details,
		Entity:      payloadFields.Entity,
		Source:      payloadFields.Source,
		Priority:    payloadFields.Priority,
		User:        payloadFields.User,
		Note:        payloadFields.Note,
	}

	return result, nil
}

// sendAlert sends an alert to OpsGenie using the specified URL and API key.
func (s *Service) sendAlert(serviceURL, apiKey string, payload *AlertPayload) error {
	jsonBody, err := json.Marshal(payload)
	if err != nil {
		return fmt.Errorf("marshaling alert payload to JSON: %w", err)
	}

	jsonBuffer := bytes.NewBuffer(jsonBody)

	ctx, cancel := context.WithTimeout(
		context.Background(),
		defaultHTTPTimeout,
	)
	defer cancel()

	req, err := http.NewRequestWithContext(
		ctx,
		http.MethodPost,
		serviceURL,
		jsonBuffer,
	)
	if err != nil {
		return fmt.Errorf("creating HTTP request: %w", err)
	}

	req.Header.Add("Authorization", "GenieKey "+apiKey)
	req.Header.Add("Content-Type", "application/json")

	client := s.httpClient
	if client == nil {
		client = &http.Client{}
	}

	resp, err := client.Do(req)
	if err != nil {
		return fmt.Errorf("failed to send notification to OpsGenie: %w", err)
	}

	defer func() { _ = resp.Body.Close() }()

	if resp.StatusCode < http.StatusOK || resp.StatusCode > httpSuccessMax {
		body, err := io.ReadAll(resp.Body)
		if err != nil {
			return fmt.Errorf(
				"%w: %d, cannot read body: %w",
				ErrUnexpectedStatus,
				resp.StatusCode,
				err,
			)
		}

		return fmt.Errorf(
			"%w: %d - %s",
			ErrUnexpectedStatus,
			resp.StatusCode,
			body,
		)
	}

	return nil
}
