package api

import (
	"crypto/tls"
	"errors"
	"fmt"
	"net/http"
	"net/url"
	"os"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/hashicorp/go-cleanhttp"
	"github.com/hashicorp/go-rootcerts"
)

const EnvVaultAddress = "VAULT_ADDR"
const EnvVaultCACert = "VAULT_CACERT"
const EnvVaultCAPath = "VAULT_CAPATH"
const EnvVaultClientCert = "VAULT_CLIENT_CERT"
const EnvVaultClientKey = "VAULT_CLIENT_KEY"
const EnvVaultInsecure = "VAULT_SKIP_VERIFY"
const EnvVaultTLSServerName = "VAULT_TLS_SERVER_NAME"

var (
	errRedirect = errors.New("redirect")
)

// Config is used to configure the creation of the client.
type Config struct {
	// Address is the address of the Vault server. This should be a complete
	// URL such as "http://vault.example.com". If you need a custom SSL
	// cert or want to enable insecure mode, you need to specify a custom
	// HttpClient.
	Address string

	// HttpClient is the HTTP client to use, which will currently always have the
	// same values as http.DefaultClient. This is used to control redirect behavior.
	HttpClient *http.Client

	redirectSetup sync.Once
}

// DefaultConfig returns a default configuration for the client. It is
// safe to modify the return value of this function.
//
// The default Address is https://127.0.0.1:8200, but this can be overridden by
// setting the `VAULT_ADDR` environment variable.
func DefaultConfig() *Config {
	config := &Config{
		Address: "https://127.0.0.1:8200",

		HttpClient: cleanhttp.DefaultClient(),
	}
	config.HttpClient.Timeout = time.Second * 60
	transport := config.HttpClient.Transport.(*http.Transport)
	transport.TLSHandshakeTimeout = 10 * time.Second
	transport.TLSClientConfig = &tls.Config{
		MinVersion: tls.VersionTLS12,
	}

	if v := os.Getenv(EnvVaultAddress); v != "" {
		config.Address = v
	}

	return config
}

// ReadEnvironment reads configuration information from the
// environment. If there is an error, no configuration value
// is updated.
func (c *Config) ReadEnvironment() error {
	var envAddress string
	var envCACert string
	var envCAPath string
	var envClientCert string
	var envClientKey string
	var envInsecure bool
	var foundInsecure bool
	var envTLSServerName string

	var clientCert tls.Certificate
	var foundClientCert bool
	var err error

	if v := os.Getenv(EnvVaultAddress); v != "" {
		envAddress = v
	}
	if v := os.Getenv(EnvVaultCACert); v != "" {
		envCACert = v
	}
	if v := os.Getenv(EnvVaultCAPath); v != "" {
		envCAPath = v
	}
	if v := os.Getenv(EnvVaultClientCert); v != "" {
		envClientCert = v
	}
	if v := os.Getenv(EnvVaultClientKey); v != "" {
		envClientKey = v
	}
	if v := os.Getenv(EnvVaultInsecure); v != "" {
		var err error
		envInsecure, err = strconv.ParseBool(v)
		if err != nil {
			return fmt.Errorf("Could not parse VAULT_SKIP_VERIFY")
		}
		foundInsecure = true
	}
	if v := os.Getenv(EnvVaultTLSServerName); v != "" {
		envTLSServerName = v
	}
	// If we need custom TLS configuration, then set it
	if envCACert != "" || envCAPath != "" || envClientCert != "" || envClientKey != "" || envInsecure {
		if envClientCert != "" && envClientKey != "" {
			clientCert, err = tls.LoadX509KeyPair(envClientCert, envClientKey)
			if err != nil {
				return err
			}
			foundClientCert = true
		} else if envClientCert != "" || envClientKey != "" {
			return fmt.Errorf("Both client cert and client key must be provided")
		}
	}

	if envAddress != "" {
		c.Address = envAddress
	}

	clientTLSConfig := c.HttpClient.Transport.(*http.Transport).TLSClientConfig
	if foundInsecure {
		clientTLSConfig.InsecureSkipVerify = envInsecure
	}

	if foundClientCert {
		clientTLSConfig.Certificates = []tls.Certificate{clientCert}
	}
	if envTLSServerName != "" {
		clientTLSConfig.ServerName = envTLSServerName
	}

	rootConfig := &rootcerts.Config{
		CAFile: envCACert,
		CAPath: envCAPath,
	}
	err = rootcerts.ConfigureTLS(clientTLSConfig, rootConfig)
	if err != nil {
		return err
	}

	return nil
}

// Client is the client to the Vault API. Create a client with
// NewClient.
type Client struct {
	addr   *url.URL
	config *Config
	token  string
}

// NewClient returns a new client for the given configuration.
//
// If the environment variable `VAULT_TOKEN` is present, the token will be
// automatically added to the client. Otherwise, you must manually call
// `SetToken()`.
func NewClient(c *Config) (*Client, error) {

	u, err := url.Parse(c.Address)
	if err != nil {
		return nil, err
	}

	if c.HttpClient == nil {
		c.HttpClient = DefaultConfig().HttpClient
	}

	redirFunc := func() {
		// Ensure redirects are not automatically followed
		// Note that this is sane for the API client as it has its own
		// redirect handling logic (and thus also for command/meta),
		// but in e.g. http_test actual redirect handling is necessary
		c.HttpClient.CheckRedirect = func(req *http.Request, via []*http.Request) error {
			return errRedirect
		}
	}

	c.redirectSetup.Do(redirFunc)

	client := &Client{
		addr:   u,
		config: c,
	}

	if token := os.Getenv("VAULT_TOKEN"); token != "" {
		client.SetToken(token)
	}

	return client, nil
}

// Token returns the access token being used by this client. It will
// return the empty string if there is no token set.
func (c *Client) Token() string {
	return c.token
}

// SetToken sets the token directly. This won't perform any auth
// verification, it simply sets the token properly for future requests.
func (c *Client) SetToken(v string) {
	c.token = v
}

// ClearToken deletes the token if it is set or does nothing otherwise.
func (c *Client) ClearToken() {
	c.token = ""
}

// NewRequest creates a new raw request object to query the Vault server
// configured for this client. This is an advanced method and generally
// doesn't need to be called externally.
func (c *Client) NewRequest(method, path string) *Request {
	req := &Request{
		Method: method,
		URL: &url.URL{
			Scheme: c.addr.Scheme,
			Host:   c.addr.Host,
			Path:   path,
		},
		ClientToken: c.token,
		Params:      make(map[string][]string),
	}

	return req
}

// RawRequest performs the raw request given. This request may be against
// a Vault server not configured with this client. This is an advanced operation
// that generally won't need to be called externally.
func (c *Client) RawRequest(r *Request) (*Response, error) {
	redirectCount := 0
START:
	req, err := r.ToHTTP()
	if err != nil {
		return nil, err
	}

	var result *Response
	resp, err := c.config.HttpClient.Do(req)
	if resp != nil {
		result = &Response{Response: resp}
	}
	if err != nil {
		if urlErr, ok := err.(*url.Error); ok && urlErr.Err == errRedirect {
			err = nil
		} else if strings.Contains(err.Error(), "tls: oversized") {
			err = fmt.Errorf(
				"%s\n\n"+
					"This error usually means that the server is running with TLS disabled\n"+
					"but the client is configured to use TLS. Please either enable TLS\n"+
					"on the server or run the client with -address set to an address\n"+
					"that uses the http protocol:\n\n"+
					"    vault <command> -address http://<address>\n\n"+
					"You can also set the VAULT_ADDR environment variable:\n\n\n"+
					"    VAULT_ADDR=http://<address> vault <command>\n\n"+
					"where <address> is replaced by the actual address to the server.",
				err)
		}
	}
	if err != nil {
		return result, err
	}

	// Check for a redirect, only allowing for a single redirect
	if (resp.StatusCode == 301 || resp.StatusCode == 302 || resp.StatusCode == 307) && redirectCount == 0 {
		// Parse the updated location
		respLoc, err := resp.Location()
		if err != nil {
			return result, err
		}

		// Ensure a protocol downgrade doesn't happen
		if req.URL.Scheme == "https" && respLoc.Scheme != "https" {
			return result, fmt.Errorf("redirect would cause protocol downgrade")
		}

		// Update the request
		r.URL = respLoc

		// Reset the request body if any
		if err := r.ResetJSONBody(); err != nil {
			return result, err
		}

		// Retry the request
		redirectCount++
		goto START
	}

	if err := result.Error(); err != nil {
		return result, err
	}

	return result, nil
}