package starssh

import (
	"bufio"
	"context"
	"io"
	"net"
	"sync"
	"sync/atomic"
	"time"

	"github.com/pkg/sftp"
	"golang.org/x/crypto/ssh"
)

const (
	defaultSSHPort           = 22
	defaultLoginTimeout      = 5 * time.Second
	defaultSSHAgentTimeout   = 2 * time.Minute
	defaultKeepAliveTimeout  = 3 * time.Second
	defaultShellPollInterval = 120 * time.Millisecond
	defaultShellSetupDelay   = 200 * time.Millisecond
	defaultShellSetupTimeout = 3 * time.Second
	defaultShellWaitTimeout  = 30 * time.Second
	defaultShellPromptToken  = "__STARSSH_PROMPT__>"
	defaultPTYTerm           = "xterm"
	defaultPTYRows           = 500
	defaultPTYColumns        = 250

	defaultTransferBufferSize = 1024 * 1024

	defaultExecStreamMaxPendingChunks = 256
	defaultExecStreamMaxPendingBytes  = 4 * 1024 * 1024
)

type DialContextFunc func(ctx context.Context, network, address string) (net.Conn, error)

type ProxyType string

const (
	ProxyTypeSOCKS5      ProxyType = "socks5"
	ProxyTypeHTTPConnect ProxyType = "http_connect"
)

type ProxyConfig struct {
	Type     ProxyType
	Addr     string
	Username string
	Password string
	Timeout  time.Duration
}

type AuthMethodKind string

const (
	AuthMethodPrivateKey          AuthMethodKind = "private_key"
	AuthMethodPassword            AuthMethodKind = "password"
	AuthMethodKeyboardInteractive AuthMethodKind = "keyboard_interactive"
	AuthMethodSSHAgent            AuthMethodKind = "ssh_agent"
)

type SSHAgentDebugFunc func(SSHAgentDebugEvent)

type SSHAgentDebugEvent struct {
	Step     string
	Source   string
	Endpoint string
	Network  string
	Phase    string
	Status   string
	Duration time.Duration
	KeyCount int
	Err      error
}

type StarSSH struct {
	stateMu        sync.RWMutex
	Client         *ssh.Client
	PublicKey      ssh.PublicKey
	PubkeyBase64   string
	Hostname       string
	RemoteAddr     net.Addr
	Banner         string
	LoginInfo      LoginInput
	online         bool
	upstream       *StarSSH
	sftpClient     *sftp.Client
	sftpMu         sync.Mutex
	agentForwardMu sync.Mutex
	agentForwarder io.Closer
	keepaliveMu    sync.Mutex
	keepaliveStop  chan struct{}
	keepaliveDone  chan struct{}
	closing        atomic.Bool
}

type LoginInput struct {
	KeyExchanges                []string
	Ciphers                     []string
	MACs                        []string
	User                        string
	Password                    string
	PasswordCallback            func() (string, error)
	KeyboardInteractiveCallback ssh.KeyboardInteractiveChallenge
	Prikey                      string
	PrikeyPwd                   string
	DisableSSHAgent             bool
	ForwardSSHAgent             bool
	AuthOrder                   []AuthMethodKind
	// IdentityAgent overrides the local ssh-agent endpoint used for authentication
	// and agent forwarding. Empty uses SSH_AUTH_SOCK, or the platform default where
	// one exists.
	IdentityAgent string
	Addr          string
	Port          int
	// Timeout limits the SSH handshake/authentication phase after a TCP connection has
	// already been established. Zero means no authentication timeout.
	Timeout time.Duration
	// DialTimeout limits outbound dial steps such as TCP connect, proxy connect, and
	// local ssh-agent socket connect. Zero falls back to Timeout when set, otherwise
	// uses the package default dial timeout. Negative disables the default dial timeout.
	DialTimeout time.Duration
	// SSHAgentTimeout limits ssh-agent protocol operations such as listing keys and
	// signing challenges. Zero uses the package default, and negative disables the
	// per-operation deadline. This is intentionally separate from Timeout and
	// DialTimeout because hardware-backed agents may require a PIN or touch confirmation.
	SSHAgentTimeout time.Duration
	// SSHAgentForwardTimeout limits idle reads and writes on forwarded agent
	// channels. Zero or negative leaves forwarded channels without an idle deadline.
	SSHAgentForwardTimeout time.Duration
	// SSHAgentDebug receives structured ssh-agent dial/protocol events. It is nil by
	// default and must not log private key material.
	SSHAgentDebug     SSHAgentDebugFunc
	DialContext       DialContextFunc
	Proxy             *ProxyConfig
	Jump              *LoginInput
	KeepAliveInterval time.Duration
	KeepAliveTimeout  time.Duration
	HostKeyCallback   func(string, net.Addr, ssh.PublicKey) error
	BannerCallback    func(string) error
}

// StarShell keeps the legacy prompt-driven helper for POSIX-style scripted shell interactions.
// It is not a generic cross-shell abstraction; for product-grade interactive terminals, prefer TerminalSession.
type StarShell struct {
	Keyword        string
	UseWaitDefault bool
	WaitTimeout    time.Duration
	Session        *ssh.Session
	in             io.Writer
	out            *bufio.Reader
	er             *bufio.Reader
	outbyte        []byte
	errbyte        []byte
	lastout        int64
	errors         error
	isprint        bool
	isfuncs        bool
	iscolor        bool
	isecho         bool
	rw             sync.RWMutex
	funcs          func(string)
	writeMu        sync.Mutex
	commandMu      sync.Mutex
	closeOnce      sync.Once
	promptToken    string
}

type TerminalConfig struct {
	Term    string
	Rows    int
	Columns int
	Modes   ssh.TerminalModes
}

type TerminalControl byte

const (
	TerminalControlInterrupt    TerminalControl = 0x03
	TerminalControlEOF          TerminalControl = 0x04
	TerminalControlBell         TerminalControl = 0x07
	TerminalControlBackspace    TerminalControl = 0x08
	TerminalControlLineKill     TerminalControl = 0x15
	TerminalControlQuit         TerminalControl = 0x1c
	TerminalControlSuspend      TerminalControl = 0x1a
	TerminalControlPauseOutput  TerminalControl = 0x13
	TerminalControlResumeOutput TerminalControl = 0x11
)

type TerminalCloseReason string

const (
	TerminalCloseReasonUnknown          TerminalCloseReason = ""
	TerminalCloseReasonExit             TerminalCloseReason = "exit"
	TerminalCloseReasonSignal           TerminalCloseReason = "signal"
	TerminalCloseReasonClosed           TerminalCloseReason = "closed"
	TerminalCloseReasonContextCanceled  TerminalCloseReason = "context_canceled"
	TerminalCloseReasonDeadlineExceeded TerminalCloseReason = "deadline_exceeded"
	TerminalCloseReasonTransportError   TerminalCloseReason = "transport_error"
)

type TerminalExitInfo struct {
	ExitCode    int
	ExitSignal  string
	ExitMessage string
	Reason      TerminalCloseReason
}

type TerminalSession struct {
	Session  *ssh.Session
	ID       string
	Label    string
	Metadata map[string]string
	stdin    io.WriteCloser
	stdout   io.Reader
	stderr   io.Reader

	attachMu sync.RWMutex
	in       io.Reader
	out      io.Writer
	errOut   io.Writer

	runOnce sync.Once
	runDone chan struct{}
	runErr  error

	waitOnce sync.Once
	waitDone chan struct{}

	stateMu     sync.RWMutex
	waitErr     error
	exitInfo    TerminalExitInfo
	closeReason TerminalCloseReason
	closeErr    error

	closeOnce sync.Once
}