package main

import (
	"net"
	"sync"
	"time"

	"github.com/racingmars/go3270"
)

// Telnet Command Constants (RFC 854 / RFC 885)
const (
	IAC  byte = 0xFF
	DONT byte = 0xFE
	DO   byte = 0xFD
	WONT byte = 0xFC
	WILL byte = 0xFB
	SB   byte = 0xFA
	GA   byte = 0xF9
	NOP  byte = 0xF1
	SE   byte = 0xF0
	EOR  byte = 0xEF

	OPT_BINARY        byte = 0x00
	OPT_SUPPRESS_GA   byte = 0x03
	OPT_TIME_MARK     byte = 0x06
	OPT_TERMINAL_TYPE byte = 0x18
	OPT_EOR           byte = 0x19
	OPT_TN3270E       byte = 0x28

	// Terminal-Type Subnegotiation Codes (RFC 1091)
	TTYPE_IS   byte = 0x00
	TTYPE_SEND byte = 0x01

	// TN3270E Subnegotiation Command Codes (RFC 2355)
	TN3270E_DEVICE_TYPE byte = 0x02
	TN3270E_FUNCTIONS   byte = 0x03
	TN3270E_IS          byte = 0x04
	TN3270E_REJECT      byte = 0x06
	TN3270E_REQUEST     byte = 0x07
	TN3270E_SEND        byte = 0x08

	// Data Types in TN3270E Header
	TN3270E_DATA_3270    byte = 0x00
	TN3270E_DATA_RESP    byte = 0x02
	TN3270E_DATA_BIND    byte = 0x03
	TN3270E_DATA_UNBIND  byte = 0x04
	TN3270E_DATA_SSCP_LU byte = 0x07

	// Functions & Header Flags in RFC 2355
	TN3270E_FUNC_BIND_IMAGE byte   = 0x00
	TN3270E_FUNC_RESPONSES  byte   = 0x02
	TN3270E_RESP_ALWAYS     byte   = 0x02
	TN3270E_UNBIND_NORMAL   byte   = 0x01
	TN3270E_MAX_SEQ         uint16 = 0x7FFF

	// 3270 Command Codes
	CMD_WRITE                 byte = 0xF1
	CMD_WSF                   byte = 0xF3
	CMD_ERASE_WRITE           byte = 0xF5
	CMD_ERASE_WRITE_SNA       byte = 0x05
	CMD_ERASE_WRITE_ALT       byte = 0x7E
	CMD_ERASE_WRITE_ALT_SNA   byte = 0x0D
	CMD_ERASE_ALL_UNPROTECTED byte = 0x6F

	// 3270 Structured Field & Query Reply Constants
	AID_QUERY_REPLY       byte = 0x88
	SF_READ_PARTITION     byte = 0x01
	SF_RP_QUERY           byte = 0xFF
	SF_QUERY_REPLY        byte = 0x81
	QR_USABLE_AREA        byte = 0x81
	QR_COLOR              byte = 0x86
	QR_HIGHLIGHTING       byte = 0x87
	QR_IMPLICIT_PARTITION byte = 0xA6
	QR_NULL               byte = 0xFF

	// 3270 Extended Color & Highlighting Attribute Constants
	ATTR_COLOR_BLUE      byte = 0xF1
	ATTR_COLOR_RED       byte = 0xF2
	ATTR_COLOR_PINK      byte = 0xF3
	ATTR_COLOR_GREEN     byte = 0xF4
	ATTR_COLOR_TURQUOISE byte = 0xF5
	ATTR_COLOR_YELLOW    byte = 0xF6
	ATTR_COLOR_WHITE     byte = 0xF7

	ATTR_HL_BLINK      byte = 0xF1
	ATTR_HL_REVERSE    byte = 0xF2
	ATTR_HL_UNDERSCORE byte = 0xF4
)

type LoginCredentials struct {
	Username   string
	Password   string
	SessionKey string
}

type AuthResult struct {
	OK      bool
	Reason  string
	IsAdmin bool
}

type TargetSystem struct {
	Name               string `toml:"name"`
	Description        string `toml:"description"`
	HostPort           string `toml:"host_port"`
	TLS                bool   `toml:"tls"`
	InsecureSkipVerify bool   `toml:"insecure_skip_verify"`
}

type ServerConfig struct {
	BindAddress          string `toml:"bind_address"`
	Codepage             string `toml:"codepage"`
	TLS                  bool   `toml:"tls"`
	CertFile             string `toml:"cert_file"`
	KeyFile              string `toml:"key_file"`
	Public               bool   `toml:"public"`
	AutoHoldDiscardLimit int    `toml:"auto_hold_discard_limit"`
	AutoHoldBurstLimit   int    `toml:"auto_hold_burst_limit"`
}

type LoginConfig struct {
	Title          string `toml:"title"`
	Subtitle       string `toml:"subtitle"`
	PromptUsername string `toml:"prompt_username"`
	PromptPassword string `toml:"prompt_password"`
	Instructions   string `toml:"instructions"`
}

type MenuConfig struct {
	Title        string `toml:"title"`
	PromptSelect string `toml:"prompt_select"`
	Footer       string `toml:"footer"`
}

type UserConfig struct {
	Username string `toml:"username"`
	Hash     string `toml:"hash"`
	Password string `toml:"password"`
	Admin    bool   `toml:"admin"`
}

type Config struct {
	Public  bool           `toml:"public"`
	Server  ServerConfig   `toml:"server"`
	Login   LoginConfig    `toml:"login"`
	Menu    MenuConfig     `toml:"menu"`
	Systems []TargetSystem `toml:"systems"`
	Users   []UserConfig   `toml:"users"`
}

const (
	defaultAutoHoldDiscardLimit = 5
	autoHoldDiscardWindow       = 5 * time.Second
	defaultAutoHoldBurstLimit   = 20
	autoHoldBurstWindow         = 1 * time.Second
)

type SessionSlot struct {
	System               TargetSystem
	Upstream             net.Conn
	LastScreen           []byte
	ScreenChanged        bool
	IsTN3270E            bool
	IsBound              bool
	SeqNumber            uint16
	IsHeld               bool
	MaxBufferSize        int
	DiscardCount         int
	DiscardWindow        time.Time
	WriteBurstCount      int
	WriteBurstWindow     time.Time
	AutoHoldDiscardLimit int
	AutoHoldBurstLimit   int
	Mu                   sync.Mutex
}

func (s *SessionSlot) resetHoldAndLoopCountersLocked() {
	s.IsHeld = false
	s.ScreenChanged = false
	s.DiscardCount = 0
	s.DiscardWindow = time.Time{}
	s.WriteBurstCount = 0
	s.WriteBurstWindow = time.Time{}
}

type slotRenderInfo struct {
	status    string
	color     go3270.Color
	hasNotice bool
}

type UserMasterSession struct {
	Username       string
	SessionKey     string
	DisplayTag     string
	TerminalType   string
	DevInfo        go3270.DevInfo
	ClientConn     net.Conn
	ActiveSlotIdx  int
	Slots          []*SessionSlot
	IsDisconnected bool
	MenuPage       int
	IsAdmin        bool
	Mu             sync.Mutex
}

func (u *UserConfig) GetHash() string {
	if u.Hash != "" {
		return u.Hash
	}
	return u.Password
}

func (s *UserMasterSession) Identity() (username, displayTag string) {
	s.Mu.Lock()
	defer s.Mu.Unlock()
	return s.Username, s.DisplayTag
}

func (s *UserMasterSession) Codepage() go3270.Codepage {
	s.Mu.Lock()
	defer s.Mu.Unlock()
	return s.codepageLocked()
}

func (s *UserMasterSession) codepageLocked() go3270.Codepage {
	if s.DevInfo != nil {
		return s.DevInfo.Codepage()
	}
	return nil
}

func (s *UserMasterSession) CountActiveSlots() int {
	s.Mu.Lock()
	defer s.Mu.Unlock()
	return s.countActiveSlotsLocked()
}

func (s *UserMasterSession) countActiveSlotsLocked() int {
	count := 0
	for _, slot := range s.Slots {
		if slot != nil {
			count++
		}
	}
	return count
}

func (s *UserMasterSession) GetMatrix() (rows, cols, maxBuf int) {
	s.Mu.Lock()
	defer s.Mu.Unlock()
	return GetTerminalMatrix(s.TerminalType, s.DevInfo)
}