//
// Copyright (c) 2018, Joyent, Inc. All rights reserved.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.
//

package client

import (
	"bytes"
	"context"
	"crypto/tls"
	"encoding/json"
	"fmt"
	"io"
	"net"
	"net/http"
	"net/url"
	"os"
	"time"

	"github.com/joyent/triton-go"
	"github.com/joyent/triton-go/authentication"
	"github.com/joyent/triton-go/errors"
	pkgerrors "github.com/pkg/errors"
)

const nilContext = "nil context"

var (
	ErrDefaultAuth = pkgerrors.New("default SSH agent authentication requires SDC_KEY_ID / TRITON_KEY_ID and SSH_AUTH_SOCK")
	ErrAccountName = pkgerrors.New("missing account name")
	ErrMissingURL  = pkgerrors.New("missing API URL")

	InvalidTritonURL = "invalid format of Triton URL"
	InvalidMantaURL  = "invalid format of Manta URL"
)

// Client represents a connection to the Triton Compute or Object Storage APIs.
type Client struct {
	HTTPClient  *http.Client
	Authorizers []authentication.Signer
	TritonURL   url.URL
	MantaURL    url.URL
	AccountName string
	Username    string
}

// New is used to construct a Client in order to make API
// requests to the Triton API.
//
// At least one signer must be provided - example signers include
// authentication.PrivateKeySigner and authentication.SSHAgentSigner.
func New(tritonURL string, mantaURL string, accountName string, signers ...authentication.Signer) (*Client, error) {
	if accountName == "" {
		return nil, ErrAccountName
	}

	if tritonURL == "" && mantaURL == "" {
		return nil, ErrMissingURL
	}

	cloudURL, err := url.Parse(tritonURL)
	if err != nil {
		return nil, pkgerrors.Wrapf(err, InvalidTritonURL)
	}

	storageURL, err := url.Parse(mantaURL)
	if err != nil {
		return nil, pkgerrors.Wrapf(err, InvalidMantaURL)
	}

	authorizers := make([]authentication.Signer, 0)
	for _, key := range signers {
		if key != nil {
			authorizers = append(authorizers, key)
		}
	}

	newClient := &Client{
		HTTPClient: &http.Client{
			Transport:     httpTransport(false),
			CheckRedirect: doNotFollowRedirects,
		},
		Authorizers: authorizers,
		TritonURL:   *cloudURL,
		MantaURL:    *storageURL,
		AccountName: accountName,
	}

	// Default to constructing an SSHAgentSigner if there are no other signers
	// passed into NewClient and there's an TRITON_KEY_ID and SSH_AUTH_SOCK
	// available in the user's environ(7).
	if len(newClient.Authorizers) == 0 {
		if err := newClient.DefaultAuth(); err != nil {
			return nil, err
		}
	}

	return newClient, nil
}

var envPrefixes = []string{"TRITON", "SDC"}

// GetTritonEnv looks up environment variables using the preferred "TRITON"
// prefix, but falls back to the SDC prefix.  For example, looking up "USER"
// will search for "TRITON_USER" followed by "SDC_USER".  If the environment
// variable is not set, an empty string is returned.  GetTritonEnv() is used to
// aid in the transition and deprecation of the SDC_* environment variables.
func GetTritonEnv(name string) string {
	for _, prefix := range envPrefixes {
		if val, found := os.LookupEnv(prefix + "_" + name); found {
			return val
		}
	}

	return ""
}

// initDefaultAuth provides a default key signer for a client. This should only
// be used internally if the client has no other key signer for authenticating
// with Triton. We first look for both `SDC_KEY_ID` and `SSH_AUTH_SOCK` in the
// user's environ(7). If so we default to the SSH agent key signer.
func (c *Client) DefaultAuth() error {
	tritonKeyId := GetTritonEnv("KEY_ID")
	if tritonKeyId != "" {
		input := authentication.SSHAgentSignerInput{
			KeyID:       tritonKeyId,
			AccountName: c.AccountName,
			Username:    c.Username,
		}
		defaultSigner, err := authentication.NewSSHAgentSigner(input)
		if err != nil {
			return pkgerrors.Wrapf(err, "unable to initialize NewSSHAgentSigner")
		}
		c.Authorizers = append(c.Authorizers, defaultSigner)
	}

	return ErrDefaultAuth
}

// InsecureSkipTLSVerify turns off TLS verification for the client connection. This
// allows connection to an endpoint with a certificate which was signed by a non-
// trusted CA, such as self-signed certificates. This can be useful when connecting
// to temporary Triton installations such as Triton Cloud-On-A-Laptop.
func (c *Client) InsecureSkipTLSVerify() {
	if c.HTTPClient == nil {
		return
	}

	c.HTTPClient.Transport = httpTransport(true)
}

func httpTransport(insecureSkipTLSVerify bool) *http.Transport {
	return &http.Transport{
		Proxy: http.ProxyFromEnvironment,
		Dial: (&net.Dialer{
			Timeout:   30 * time.Second,
			KeepAlive: 30 * time.Second,
		}).Dial,
		TLSHandshakeTimeout: 10 * time.Second,
		MaxIdleConns:        10,
		IdleConnTimeout:     15 * time.Second,
		TLSClientConfig: &tls.Config{
			InsecureSkipVerify: insecureSkipTLSVerify,
		},
	}
}

func doNotFollowRedirects(*http.Request, []*http.Request) error {
	return http.ErrUseLastResponse
}

func (c *Client) DecodeError(resp *http.Response, requestMethod string) error {
	err := &errors.APIError{
		StatusCode: resp.StatusCode,
	}

	if requestMethod != http.MethodHead && resp.Body != nil {
		errorDecoder := json.NewDecoder(resp.Body)
		if err := errorDecoder.Decode(err); err != nil {
			return pkgerrors.Wrapf(err, "unable to decode error response")
		}
	}

	if err.Message == "" {
		err.Message = fmt.Sprintf("HTTP response returned status code %d", err.StatusCode)
	}

	return err
}

// -----------------------------------------------------------------------------

type RequestInput struct {
	Method  string
	Path    string
	Query   *url.Values
	Headers *http.Header
	Body    interface{}
}

func (c *Client) ExecuteRequestURIParams(ctx context.Context, inputs RequestInput) (io.ReadCloser, error) {
	method := inputs.Method
	path := inputs.Path
	body := inputs.Body
	query := inputs.Query

	var requestBody io.Reader
	if body != nil {
		marshaled, err := json.MarshalIndent(body, "", "    ")
		if err != nil {
			return nil, err
		}
		requestBody = bytes.NewReader(marshaled)
	}

	endpoint := c.TritonURL
	endpoint.Path = path
	if query != nil {
		endpoint.RawQuery = query.Encode()
	}

	req, err := http.NewRequest(method, endpoint.String(), requestBody)
	if err != nil {
		return nil, pkgerrors.Wrapf(err, "unable to construct HTTP request")
	}

	dateHeader := time.Now().UTC().Format(time.RFC1123)
	req.Header.Set("date", dateHeader)

	// NewClient ensures there's always an authorizer (unless this is called
	// outside that constructor).
	authHeader, err := c.Authorizers[0].Sign(dateHeader)
	if err != nil {
		return nil, pkgerrors.Wrapf(err, "unable to sign HTTP request")
	}
	req.Header.Set("Authorization", authHeader)
	req.Header.Set("Accept", "application/json")
	req.Header.Set("Accept-Version", triton.CloudAPIMajorVersion)
	req.Header.Set("User-Agent", triton.UserAgent())

	if body != nil {
		req.Header.Set("Content-Type", "application/json")
	}

	resp, err := c.HTTPClient.Do(req.WithContext(ctx))
	if err != nil {
		return nil, pkgerrors.Wrapf(err, "unable to execute HTTP request")
	}

	// We will only return a response from the API it is in the HTTP StatusCode 2xx range
	// StatusMultipleChoices is StatusCode 300
	if resp.StatusCode >= http.StatusOK && resp.StatusCode < http.StatusMultipleChoices {
		return resp.Body, nil
	}

	return nil, c.DecodeError(resp, req.Method)
}

func (c *Client) ExecuteRequest(ctx context.Context, inputs RequestInput) (io.ReadCloser, error) {
	return c.ExecuteRequestURIParams(ctx, inputs)
}

func (c *Client) ExecuteRequestRaw(ctx context.Context, inputs RequestInput) (*http.Response, error) {
	method := inputs.Method
	path := inputs.Path
	body := inputs.Body

	var requestBody io.Reader
	if body != nil {
		marshaled, err := json.MarshalIndent(body, "", "    ")
		if err != nil {
			return nil, err
		}
		requestBody = bytes.NewReader(marshaled)
	}

	endpoint := c.TritonURL
	endpoint.Path = path

	req, err := http.NewRequest(method, endpoint.String(), requestBody)
	if err != nil {
		return nil, pkgerrors.Wrapf(err, "unable to construct HTTP request")
	}

	dateHeader := time.Now().UTC().Format(time.RFC1123)
	req.Header.Set("date", dateHeader)

	// NewClient ensures there's always an authorizer (unless this is called
	// outside that constructor).
	authHeader, err := c.Authorizers[0].Sign(dateHeader)
	if err != nil {
		return nil, pkgerrors.Wrapf(err, "unable to sign HTTP request")
	}
	req.Header.Set("Authorization", authHeader)
	req.Header.Set("Accept", "application/json")
	req.Header.Set("Accept-Version", triton.CloudAPIMajorVersion)
	req.Header.Set("User-Agent", triton.UserAgent())

	if body != nil {
		req.Header.Set("Content-Type", "application/json")
	}

	resp, err := c.HTTPClient.Do(req.WithContext(ctx))
	if err != nil {
		return nil, pkgerrors.Wrapf(err, "unable to execute HTTP request")
	}

	// We will only return a response from the API it is in the HTTP StatusCode 2xx range
	// StatusMultipleChoices is StatusCode 300
	if resp.StatusCode >= http.StatusOK && resp.StatusCode < http.StatusMultipleChoices {
		return resp, nil
	}

	return nil, c.DecodeError(resp, req.Method)
}

func (c *Client) ExecuteRequestStorage(ctx context.Context, inputs RequestInput) (io.ReadCloser, http.Header, error) {
	method := inputs.Method
	path := inputs.Path
	query := inputs.Query
	headers := inputs.Headers
	body := inputs.Body

	endpoint := c.MantaURL
	endpoint.Path = path

	var requestBody io.Reader
	if body != nil {
		marshaled, err := json.MarshalIndent(body, "", "    ")
		if err != nil {
			return nil, nil, err
		}
		requestBody = bytes.NewReader(marshaled)
	}

	req, err := http.NewRequest(method, endpoint.String(), requestBody)
	if err != nil {
		return nil, nil, pkgerrors.Wrapf(err, "unable to construct HTTP request")
	}

	if body != nil && (headers == nil || headers.Get("Content-Type") == "") {
		req.Header.Set("Content-Type", "application/json")
	}
	if headers != nil {
		for key, values := range *headers {
			for _, value := range values {
				req.Header.Set(key, value)
			}
		}
	}

	dateHeader := time.Now().UTC().Format(time.RFC1123)
	req.Header.Set("date", dateHeader)

	authHeader, err := c.Authorizers[0].Sign(dateHeader)
	if err != nil {
		return nil, nil, pkgerrors.Wrapf(err, "unable to sign HTTP request")
	}
	req.Header.Set("Authorization", authHeader)
	req.Header.Set("Accept", "*/*")
	req.Header.Set("User-Agent", triton.UserAgent())

	if query != nil {
		req.URL.RawQuery = query.Encode()
	}

	resp, err := c.HTTPClient.Do(req.WithContext(ctx))
	if err != nil {
		return nil, nil, pkgerrors.Wrapf(err, "unable to execute HTTP request")
	}

	// We will only return a response from the API it is in the HTTP StatusCode 2xx range
	// StatusMultipleChoices is StatusCode 300
	if resp.StatusCode >= http.StatusOK && resp.StatusCode < http.StatusMultipleChoices {
		return resp.Body, resp.Header, nil
	}

	return nil, nil, c.DecodeError(resp, req.Method)
}

type RequestNoEncodeInput struct {
	Method  string
	Path    string
	Query   *url.Values
	Headers *http.Header
	Body    io.Reader
}

func (c *Client) ExecuteRequestNoEncode(ctx context.Context, inputs RequestNoEncodeInput) (io.ReadCloser, http.Header, error) {
	method := inputs.Method
	path := inputs.Path
	query := inputs.Query
	headers := inputs.Headers
	body := inputs.Body

	endpoint := c.MantaURL
	endpoint.Path = path

	req, err := http.NewRequest(method, endpoint.String(), body)
	if err != nil {
		return nil, nil, pkgerrors.Wrapf(err, "unable to construct HTTP request")
	}

	if headers != nil {
		for key, values := range *headers {
			for _, value := range values {
				req.Header.Set(key, value)
			}
		}
	}

	dateHeader := time.Now().UTC().Format(time.RFC1123)
	req.Header.Set("date", dateHeader)

	authHeader, err := c.Authorizers[0].Sign(dateHeader)
	if err != nil {
		return nil, nil, pkgerrors.Wrapf(err, "unable to sign HTTP request")
	}
	req.Header.Set("Authorization", authHeader)
	req.Header.Set("Accept", "*/*")
	req.Header.Set("Accept-Version", triton.CloudAPIMajorVersion)
	req.Header.Set("User-Agent", triton.UserAgent())

	if query != nil {
		req.URL.RawQuery = query.Encode()
	}

	resp, err := c.HTTPClient.Do(req.WithContext(ctx))
	if err != nil {
		return nil, nil, pkgerrors.Wrapf(err, "unable to execute HTTP request")
	}

	// We will only return a response from the API it is in the HTTP StatusCode 2xx range
	// StatusMultipleChoices is StatusCode 300
	if resp.StatusCode >= http.StatusOK && resp.StatusCode < http.StatusMultipleChoices {
		return resp.Body, resp.Header, nil
	}

	return nil, nil, c.DecodeError(resp, req.Method)
}