package client

import (
	"fmt"
	"os"

	"github.com/mimecast/dtail/internal/config"
	"github.com/mimecast/dtail/internal/io/dlog"
	"github.com/mimecast/dtail/internal/ssh"

	gossh "golang.org/x/crypto/ssh"
)

const addedPathStr string = "Added path to list of auth methods, not adding further methods"

// InitSSHAuthMethods initialises all known SSH auth methods on the client side.
func InitSSHAuthMethods(sshAuthMethods []gossh.AuthMethod,
	hostKeyCallback gossh.HostKeyCallback, trustAllHosts bool, throttleCh chan struct{},
	privateKeyPath string) ([]gossh.AuthMethod, HostKeyCallback) {

	if len(sshAuthMethods) > 0 {
		simpleCallback, err := NewSimpleCallback()
		if err != nil {
			dlog.Client.FatalPanic(err)
		}
		return sshAuthMethods, simpleCallback
	}
	return initKnownHostsAuthMethods(trustAllHosts, throttleCh, privateKeyPath)
}

func initIntegrationTestKnownHostsAuthMethods() []gossh.AuthMethod {
	var sshAuthMethods []gossh.AuthMethod
	privateKeyPath := "./id_rsa"

	GeneratePrivatePublicKeyPairIfNotExists(privateKeyPath, 4096)
	authMethod, err := ssh.PrivateKey(privateKeyPath)
	if err != nil {
		dlog.Client.FatalPanic("Unable to use private SSH key", privateKeyPath, err)
	}

	sshAuthMethods = append(sshAuthMethods, authMethod)
	dlog.Client.Debug("initKnownHostsAuthMethods", addedPathStr, privateKeyPath)
	return sshAuthMethods
}

func initKnownHostsAuthMethods(trustAllHosts bool, throttleCh chan struct{},
	privateKeyPath string) ([]gossh.AuthMethod, HostKeyCallback) {

	var sshAuthMethods []gossh.AuthMethod
	knownHostsFile := fmt.Sprintf("%s/.ssh/known_hosts", os.Getenv("HOME"))
	if config.Env("DTAIL_INTEGRATION_TEST_RUN_MODE") {
		// In case of integration test, override known hosts file path.
		knownHostsFile = "./known_hosts"
	}

	knownHostsCallback, err := NewKnownHostsCallback(knownHostsFile, trustAllHosts, throttleCh)
	if err != nil {
		dlog.Client.FatalPanic(knownHostsFile, err)
	}
	dlog.Client.Debug("initKnownHostsAuthMethods", "Added known hosts file path", knownHostsFile)

	if config.Env("DTAIL_INTEGRATION_TEST_RUN_MODE") {
		return initIntegrationTestKnownHostsAuthMethods(), knownHostsCallback
	}

	// Try to read custom private key path.
	if privateKeyPath != "" {
		authMethod, err := ssh.PrivateKey(privateKeyPath)
		if err == nil {
			sshAuthMethods = append(sshAuthMethods, authMethod)
			dlog.Client.Debug("initKnownHostsAuthMethods", addedPathStr, privateKeyPath)
			return sshAuthMethods, knownHostsCallback
		}
		dlog.Client.FatalPanic("Unable to use private SSH key", privateKeyPath, err)
	}

	// Second, try SSH Agent
	authMethod, err := ssh.Agent()
	if err == nil {
		sshAuthMethods = append(sshAuthMethods, authMethod)
		dlog.Client.Debug("initKnownHostsAuthMethods", "Added SSH Agent (SSH_AUTH_SOCK)"+
			"to list of auth methods, not adding further methods")
		return sshAuthMethods, knownHostsCallback
	}
	dlog.Client.Debug("initKnownHostsAuthMethods", "Unable to init SSH Agent auth method", err)

	// Third, try Linux/UNIX default key paths
	privateKeyPath = os.Getenv("HOME") + "/.ssh/id_rsa"
	authMethod, err = ssh.PrivateKey(privateKeyPath)
	if err == nil {
		sshAuthMethods = append(sshAuthMethods, authMethod)
		dlog.Client.Debug("initKnownHostsAuthmethods", addedPathStr, privateKeyPath)
		return sshAuthMethods, knownHostsCallback
	}
	dlog.Client.Debug("initKnownHostsAuthMethods", "Unable to use private key", privateKeyPath, err)

	privateKeyPath = os.Getenv("HOME") + "/.ssh/id_dsa"
	authMethod, err = ssh.PrivateKey(privateKeyPath)
	if err == nil {
		sshAuthMethods = append(sshAuthMethods, authMethod)
		dlog.Client.Debug("initKnownHostsAuthmethods", addedPathStr, privateKeyPath)
		return sshAuthMethods, knownHostsCallback
	}

	privateKeyPath = os.Getenv("HOME") + "/.ssh/id_ecdsa"
	authMethod, err = ssh.PrivateKey(privateKeyPath)
	if err == nil {
		sshAuthMethods = append(sshAuthMethods, authMethod)
		dlog.Client.Debug("initKnownHostsAuthmethods", addedPathStr, privateKeyPath)
		return sshAuthMethods, knownHostsCallback
	}

	dlog.Client.FatalPanic("Unable to find private SSH key information", privateKeyPath, err)
	// Never reach this point.
	return sshAuthMethods, knownHostsCallback
}