package main

import (
	"errors"
	"fmt"
	"log"
	"net/http"
	"net/url"
	"os"
	"strconv"
	"strings"
	"time"

	"github.com/gin-gonic/gin"
	"gzzn.com/mini/ciimsproxy/internal"
)

const (
	servicePrefix            = "/services/ExchangeService"
	defaultTimeout           = 240
	maxMsgLen                = 1048576 // 1MB
	maxCount                 = 1000
	readHeaderTimeout        = 5 * time.Second
	readTimeout              = 10 * time.Second
	writeTimeoutGrace        = 10 * time.Second
	idleTimeout              = 60 * time.Second
	allowedServersEnvVarName = "CIIMS_ALLOWED_SERVERS"
)

type Config struct {
	ServerURL      string
	AllowedServers map[string]string
	Listen         string
	Timeout        int
	Client         *internal.Client
}

type App struct {
	config Config
}

type sendRequest struct {
	URL      string `json:"url"`
	User     string `json:"user" binding:"required"`
	Pass     string `json:"pass" binding:"required"`
	Event    string `json:"event" binding:"required"`
	Priority int    `json:"priority"`
	Val      bool   `json:"val"`
	Msg      string `json:"msg" binding:"required"`
}

type receiveRequest struct {
	URL   string `json:"url"`
	User  string `json:"user" binding:"required"`
	Pass  string `json:"pass" binding:"required"`
	Count int    `json:"count" binding:"required"`
}

func main() {
	config, err := loadConfig()
	if err != nil {
		log.Printf("[ERROR] configuration error: %v", err)
		os.Exit(1)
	}

	log.Printf("use ciims: %s", config.ServerURL)
	srv := newServer(config)
	log.Printf("Starting ciims proxy for %s", config.ServerURL)
	log.Printf("timeout: %d", config.Timeout)
	if err := srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
		log.Printf("[ERROR] server failed: %v", err)
		os.Exit(1)
	}
}

func loadConfig() (Config, error) {
	config := Config{
		Listen:  os.Getenv("PROXY_LISTEN"),
		Timeout: defaultTimeout,
	}

	serverURL, err := normalizeBaseURL(os.Getenv("CIIMS_SERVER"))
	if err != nil {
		return Config{}, fmt.Errorf("invalid CIIMS_SERVER: %w", err)
	}
	config.ServerURL = serverURL
	config.AllowedServers = map[string]string{serverURL: serverURL}

	allowedServers, err := parseAllowedServers(os.Getenv(allowedServersEnvVarName))
	if err != nil {
		return Config{}, err
	}
	for _, allowed := range allowedServers {
		config.AllowedServers[allowed] = allowed
	}

	t, err := getIntEnv("CIIMS_TIMEOUT")
	if err != nil {
		return Config{}, err
	}
	if t > 0 {
		config.Timeout = t
	}
	if config.Listen == "" {
		config.Listen = ":9090"
	}
	config.Client, err = internal.NewClient(config.Timeout)
	if err != nil {
		return Config{}, err
	}
	return config, nil
}

func newServer(config Config) *http.Server {
	return &http.Server{
		Addr:              config.Listen,
		Handler:           newRouter(config),
		ReadHeaderTimeout: readHeaderTimeout,
		ReadTimeout:       readTimeout,
		WriteTimeout:      time.Duration(config.Timeout)*time.Second + writeTimeoutGrace,
		IdleTimeout:       idleTimeout,
	}
}

func newRouter(config Config) *gin.Engine {
	if config.AllowedServers == nil && config.ServerURL != "" {
		config.AllowedServers = map[string]string{config.ServerURL: config.ServerURL}
	}
	app := &App{config: config}
	r := gin.Default()
	r.GET("/ping", func(c *gin.Context) {
		c.JSON(200, gin.H{
			"message": "pong",
		})
	})
	r.POST("/send", app.sendMessage)
	r.POST("/receive", app.receiveMessage)
	return r
}

func (a *App) sendMessage(c *gin.Context) {
	c.Request.Body = http.MaxBytesReader(c.Writer, c.Request.Body, maxMsgLen)

	var message sendRequest
	if err := c.ShouldBind(&message); err != nil {
		a.handleBindError(c, err)
		return
	}
	ciimsURL, ok := a.resolveTargetURL(c, message.URL)
	if !ok {
		return
	}
	msg := internal.CreateSend(message.User, message.Pass,
		message.Priority, message.Event, message.Val, message.Msg)
	resp, err := a.config.Client.Send(c.Request.Context(), ciimsURL, msg)
	if err != nil {
		a.handleSendError(c, "send", resp, err)
		return
	}
	if errMsg := resp.ErrorMessage(); errMsg != "" {
		log.Printf("[ERROR] SOAP fault: %s", errMsg)
		c.JSON(http.StatusInternalServerError, gin.H{"error": errMsg})
		return
	}
	c.JSON(http.StatusOK, gin.H{"error": ""})
}

func (a *App) receiveMessage(c *gin.Context) {
	c.Request.Body = http.MaxBytesReader(c.Writer, c.Request.Body, maxMsgLen)

	var message receiveRequest
	if err := c.ShouldBind(&message); err != nil {
		a.handleBindError(c, err)
		return
	}

	if message.Count < 1 || message.Count > maxCount {
		c.JSON(http.StatusBadRequest, gin.H{"error": "count must be between 1 and " + strconv.Itoa(maxCount)})
		return
	}

	ciimsURL, ok := a.resolveTargetURL(c, message.URL)
	if !ok {
		return
	}
	msg := internal.CreateReceive(message.User, message.Pass, message.Count)
	resp, err := a.config.Client.Send(c.Request.Context(), ciimsURL, msg)
	if err != nil {
		a.handleSendError(c, "receive", resp, err)
		return
	}
	if errMsg := resp.ErrorMessage(); errMsg != "" {
		log.Printf("[ERROR] SOAP fault: %s", errMsg)
		c.JSON(http.StatusInternalServerError, gin.H{"error": errMsg})
		return
	}
	c.JSON(http.StatusOK, gin.H{"msgs": resp.Messages()})
}

func (a *App) resolveTargetURL(c *gin.Context, requestedURL string) (string, bool) {
	targetBase, err := a.getBaseURL(requestedURL)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
		return "", false
	}
	return targetBase + servicePrefix, true
}

func (a *App) getBaseURL(requestedURL string) (string, error) {
	if strings.TrimSpace(requestedURL) == "" {
		return a.config.ServerURL, nil
	}
	normalized, err := normalizeBaseURL(requestedURL)
	if err != nil {
		return "", fmt.Errorf("invalid url: %w", err)
	}
	if _, ok := a.config.AllowedServers[normalized]; !ok {
		return "", fmt.Errorf("url is not allowed")
	}
	return normalized, nil
}

func normalizeBaseURL(raw string) (string, error) {
	raw = strings.TrimSpace(raw)
	if raw == "" {
		return "", fmt.Errorf("must not be empty")
	}
	u, err := url.Parse(raw)
	if err != nil {
		return "", err
	}
	u.Scheme = strings.ToLower(u.Scheme)
	u.Host = strings.ToLower(u.Host)
	if u.Scheme != "http" && u.Scheme != "https" {
		return "", fmt.Errorf("scheme must be http or https")
	}
	if u.Host == "" {
		return "", fmt.Errorf("host is required")
	}
	if u.RawQuery != "" || u.Fragment != "" {
		return "", fmt.Errorf("query and fragment are not allowed")
	}
	u.Path = strings.TrimRight(u.Path, "/")
	u.RawPath = ""
	return u.String(), nil
}

func parseAllowedServers(raw string) ([]string, error) {
	if strings.TrimSpace(raw) == "" {
		return nil, nil
	}
	parts := strings.Split(raw, ",")
	allowed := make([]string, 0, len(parts))
	for _, part := range parts {
		normalized, err := normalizeBaseURL(part)
		if err != nil {
			return nil, fmt.Errorf("invalid %s entry %q: %w", allowedServersEnvVarName, part, err)
		}
		allowed = append(allowed, normalized)
	}
	return allowed, nil
}

func (a *App) handleBindError(c *gin.Context, err error) {
	var maxBytesErr *http.MaxBytesError
	if errors.As(err, &maxBytesErr) {
		c.JSON(http.StatusRequestEntityTooLarge, gin.H{"error": err.Error()})
		return
	}
	log.Print(err.Error())
	c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
}

func (a *App) handleSendError(c *gin.Context, operation string, resp *internal.CIIMSResponse, err error) {
	if resp != nil {
		if errMsg := resp.ErrorMessage(); errMsg != "" {
			log.Printf("[ERROR] SOAP fault: %s", errMsg)
			c.JSON(http.StatusInternalServerError, gin.H{"error": errMsg})
			return
		}
	}
	var statusErr *internal.HTTPStatusError
	if errors.As(err, &statusErr) {
		if errMsg := internal.GetErrMsg(statusErr.Body); errMsg != "" {
			log.Printf("[ERROR] SOAP fault: %s", errMsg)
			c.JSON(http.StatusInternalServerError, gin.H{"error": errMsg})
			return
		}
	}
	log.Printf("[ERROR] %s failed: %v", operation, err)
	c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
}

func getIntEnv(key string) (int, error) {
	val := os.Getenv(key)
	if val == "" {
		return 0, nil
	}
	ret, err := strconv.Atoi(val)
	if err != nil {
		return 0, fmt.Errorf("invalid %s value %q: must be an integer", key, val)
	}
	if ret <= 0 {
		return 0, fmt.Errorf("invalid %s value %q: must be positive", key, val)
	}
	return ret, nil
}