// Package render generates frpc worker configuration (JSON) from canvas data.
package render

import (
	"encoding/json"
	"fmt"

	"webui4frpc/internal/store"
)

// Proxy is a single proxy to render inside a worker config. It carries enough
// info to build any supported frpc proxy type.
type Proxy struct {
	// Name is the display name (the local service name).
	Name string
	// Type is the proxy type: tcp | udp | http | https.
	Type string
	// LocalIP and LocalPort are the backend address.
	LocalIP   string
	LocalPort int
	// RemotePort is the exposed port on the frps server (tcp/udp only).
	RemotePort int
	// SubDomain is used by http/https proxies when set.
	SubDomain string
	// CustomDomains is used by http/https proxies when set.
	CustomDomains []string
}

// frpcAuth mirrors frpc's auth section.
type frpcAuth struct {
	Method string `json:"method"`
	Token  string `json:"token,omitempty"`
}

// frpcTransport is the transport section used by frpc.
type frpcTransport struct {
	Protocol string `json:"protocol,omitempty"`
}

// frpcProxy is the serialized proxy object. Different types use different
// fields; empty ones are omitted so the JSON is accepted by frpc.
type frpcProxy struct {
	Name          string   `json:"name"`
	Type          string   `json:"type"`
	LocalIP       string   `json:"localIP,omitempty"`
	LocalPort     int      `json:"localPort"`
	RemotePort    int      `json:"remotePort,omitempty"`
	CustomDomains []string `json:"customDomains,omitempty"`
	SubDomain     string   `json:"subdomain,omitempty"`
}

// Config is a complete frpc configuration document.
type Config struct {
	ServerAddr    string        `json:"serverAddr"`
	ServerPort    int           `json:"serverPort"`
	Auth          frpcAuth      `json:"auth"`
	Transport     frpcTransport `json:"transport,omitempty"`
	LoginFailExit bool          `json:"loginFailExit"`
	Proxies       []frpcProxy   `json:"proxies"`
}

// Render builds the worker config JSON for a remote server from its setting
// plus the list of proxies to forward.
func Render(remote store.Remote, proxies []Proxy) ([]byte, error) {
	cfg := Config{
		ServerAddr:    remote.IP,
		ServerPort:    remote.Port,
		Auth:          frpcAuth{Method: "token", Token: remote.Token},
		LoginFailExit: false,
		Proxies:       make([]frpcProxy, 0, len(proxies)),
	}

	nameCounts := make(map[string]int)
	for _, p := range proxies {
		frpcP := frpcProxy{
			Name:      p.Name,
			Type:      p.Type,
			LocalIP:   p.LocalIP,
			LocalPort: p.LocalPort,
			SubDomain: p.SubDomain,
		}
		// http/https proxies use customDomains instead of remotePort. The
		// default domain is <name>.local; frps matches it by Host header.
		if p.Type == "http" || p.Type == "https" {
			frpcP.RemotePort = 0
			if frpcP.SubDomain == "" && len(frpcP.CustomDomains) == 0 {
				frpcP.CustomDomains = []string{p.Name + ".local"}
			}
		} else {
			frpcP.RemotePort = p.RemotePort
		}
		if len(p.CustomDomains) > 0 {
			frpcP.CustomDomains = p.CustomDomains
		}
		// Duplicate service name -> suffix with the remote port so frpc accepts
		// multiple proxies for the same local service.
		nameCounts[frpcP.Name]++
		if nameCounts[frpcP.Name] > 1 {
			frpcP.Name = fmt.Sprintf("%s-%d", frpcP.Name, frpcP.RemotePort)
		}
		cfg.Proxies = append(cfg.Proxies, frpcP)
	}
	return json.MarshalIndent(cfg, "", "  ")
}