package lfshttp

import (
	"crypto/tls"
	"crypto/x509"
	"encoding/pem"
	"fmt"
	"io/ioutil"
	"net/url"
	"path/filepath"

	"github.com/git-lfs/git-lfs/config"
	"github.com/rubyist/tracerx"
)

// isCertVerificationDisabledForHost returns whether SSL certificate verification
// has been disabled for the given host, or globally
func isCertVerificationDisabledForHost(c *Client, host string) bool {
	hostSslVerify, _ := c.uc.Get("http", fmt.Sprintf("https://%v", host), "sslverify")
	if hostSslVerify == "false" {
		return true
	}

	return c.SkipSSLVerify
}

// isClientCertEnabledForHost returns whether client certificate
// are configured for the given host
func isClientCertEnabledForHost(c *Client, host string) bool {
	_, hostSslKeyOk := c.uc.Get("http", fmt.Sprintf("https://%v/", host), "sslKey")
	_, hostSslCertOk := c.uc.Get("http", fmt.Sprintf("https://%v/", host), "sslCert")

	return hostSslKeyOk && hostSslCertOk
}

// decryptPEMBlock decrypts an encrypted PEM block representing a private key,
// prompting for credentials using the credential helper, and returns a
// decrypted PEM block representing that same private key.
func decryptPEMBlock(c *Client, block *pem.Block, path string, key []byte) ([]byte, error) {
	fileurl := fmt.Sprintf("cert:///%s", filepath.ToSlash(path))
	url, err := url.Parse(fileurl)
	if err != nil {
		return nil, err
	}
	credWrapper := c.credHelperContext.GetCredentialHelper(nil, url)

	credWrapper.Input["username"] = ""

	creds, err := credWrapper.CredentialHelper.Fill(credWrapper.Input)
	if err != nil {
		tracerx.Printf("Error filling credentials for %q: %v", fileurl, err)
		return nil, err
	}
	pass := creds["password"]
	decrypted, err := x509.DecryptPEMBlock(block, []byte(pass))
	if err != nil {
		credWrapper.CredentialHelper.Reject(creds)
		return nil, err
	}
	credWrapper.CredentialHelper.Approve(creds)

	// decrypted is a DER blob, but we need a PEM-encoded block.
	toEncode := &pem.Block{Type: block.Type, Headers: nil, Bytes: decrypted}
	buf := pem.EncodeToMemory(toEncode)
	return buf, nil
}

// getClientCertForHost returns a client certificate for a specific host (which may
// be "host:port" loaded from the gitconfig
func getClientCertForHost(c *Client, host string) *tls.Certificate {
	hostSslKey, _ := c.uc.Get("http", fmt.Sprintf("https://%v/", host), "sslKey")
	hostSslCert, _ := c.uc.Get("http", fmt.Sprintf("https://%v/", host), "sslCert")

	cert, err := ioutil.ReadFile(hostSslCert)
	if err != nil {
		tracerx.Printf("Error reading client cert file %q: %v", hostSslCert, err)
		return nil
	}
	key, err := ioutil.ReadFile(hostSslKey)
	if err != nil {
		tracerx.Printf("Error reading client key file %q: %v", hostSslKey, err)
		return nil
	}

	block, _ := pem.Decode(key)
	if x509.IsEncryptedPEMBlock(block) {
		key, err = decryptPEMBlock(c, block, hostSslKey, key)
		if err != nil {
			tracerx.Printf("Unable to decrypt client key file %q: %v", hostSslKey, err)
			return nil
		}
	}

	certobj, err := tls.X509KeyPair(cert, key)
	if err != nil {
		tracerx.Printf("Error reading client cert/key %v", err)
		return nil
	}
	return &certobj
}

// getRootCAsForHost returns a certificate pool for that specific host (which may
// be "host:port" loaded from either the gitconfig or from a platform-specific
// source which is not included by default in the golang certificate search)
// May return nil if it doesn't have anything to add, in which case the default
// RootCAs will be used if passed to TLSClientConfig.RootCAs
func getRootCAsForHost(c *Client, host string) *x509.CertPool {
	// don't init pool, want to return nil not empty if none found; init only on successful add cert
	var pool *x509.CertPool

	// gitconfig first
	pool = appendRootCAsForHostFromGitconfig(c.osEnv, c.gitEnv, pool, host)
	// Platform specific
	return appendRootCAsForHostFromPlatform(pool, host)
}

func appendRootCAsForHostFromGitconfig(osEnv, gitEnv config.Environment, pool *x509.CertPool, host string) *x509.CertPool {
	url := fmt.Sprintf("https://%v/", host)
	uc := config.NewURLConfig(gitEnv)

	backend, _ := uc.Get("http", url, "sslbackend")
	schannelUseSslCaInfoStrValue, _ := uc.Get("http", url, "schannelusesslcainfo")
	schannelUseSslCaInfo := config.Bool(schannelUseSslCaInfoStrValue, false)

	if backend == "schannel" && !schannelUseSslCaInfo {
		return pool
	}

	// Accumulate certs from all these locations:

	// GIT_SSL_CAINFO first
	if cafile, _ := osEnv.Get("GIT_SSL_CAINFO"); len(cafile) > 0 {
		return appendCertsFromFile(pool, cafile)
	}
	// http.<url>/.sslcainfo or http.<url>.sslcainfo
	if cafile, ok := uc.Get("http", url, "sslcainfo"); ok {
		return appendCertsFromFile(pool, cafile)
	}
	// GIT_SSL_CAPATH
	if cadir, _ := osEnv.Get("GIT_SSL_CAPATH"); len(cadir) > 0 {
		return appendCertsFromFilesInDir(pool, cadir)
	}
	// http.sslcapath
	if cadir, ok := gitEnv.Get("http.sslcapath"); ok {
		return appendCertsFromFilesInDir(pool, cadir)
	}

	return pool
}

func appendCertsFromFilesInDir(pool *x509.CertPool, dir string) *x509.CertPool {
	files, err := ioutil.ReadDir(dir)
	if err != nil {
		tracerx.Printf("Error reading cert dir %q: %v", dir, err)
		return pool
	}
	for _, f := range files {
		pool = appendCertsFromFile(pool, filepath.Join(dir, f.Name()))
	}
	return pool
}

func appendCertsFromFile(pool *x509.CertPool, filename string) *x509.CertPool {
	data, err := ioutil.ReadFile(filename)
	if err != nil {
		tracerx.Printf("Error reading cert file %q: %v", filename, err)
		return pool
	}
	// Firstly, try parsing as binary certificate
	if certs, err := x509.ParseCertificates(data); err == nil {
		return appendCerts(pool, certs)
	}
	// If not binary certs, try PEM data
	return appendCertsFromPEMData(pool, data)
}

func appendCerts(pool *x509.CertPool, certs []*x509.Certificate) *x509.CertPool {
	if len(certs) == 0 {
		// important to return unmodified (may be nil)
		return pool
	}

	if pool == nil {
		pool = x509.NewCertPool()
	}

	for _, cert := range certs {
		pool.AddCert(cert)
	}

	return pool
}

func appendCertsFromPEMData(pool *x509.CertPool, data []byte) *x509.CertPool {
	if len(data) == 0 {
		return pool
	}

	// Bit of a dance, need to ensure if AppendCertsFromPEM fails we still return
	// nil and not an empty pool, so system roots still get used
	var ret *x509.CertPool
	if pool == nil {
		ret = x509.NewCertPool()
	} else {
		ret = pool
	}
	if !ret.AppendCertsFromPEM(data) {
		// Return unmodified input pool (may be nil, do not replace with empty)
		return pool
	}
	return ret
}
