context.go

// SPDX-License-Identifier: MIT
// SPDX-FileCopyrightText: © 2015 LabStack LLC and Echo contributors

package echo

import (
	"bytes"
	"encoding/xml"
	"fmt"
	"io"
	"mime/multipart"
	"net"
	"net/http"
	"net/url"
	"strings"
	"sync"
)

// Context represents the context of the current HTTP request. It holds request and
// response objects, path, path parameters, data and registered handler.
type Context interface {
	// Request returns `*http.Request`.
	Request() *http.Request

	// SetRequest sets `*http.Request`.
	SetRequest(r *http.Request)

	// SetResponse sets `*Response`.
	SetResponse(r *Response)

	// Response returns `*Response`.
	Response() *Response

	// IsTLS returns true if HTTP connection is TLS otherwise false.
	IsTLS() bool

	// IsWebSocket returns true if HTTP connection is WebSocket otherwise false.
	IsWebSocket() bool

	// Scheme returns the HTTP protocol scheme, `http` or `https`.
	Scheme() string

	// RealIP returns the client's network address based on `X-Forwarded-For`
	// or `X-Real-IP` request header.
	// The behavior can be configured using `Echo#IPExtractor`.
	RealIP() string

	// Path returns the registered path for the handler.
	Path() string

	// SetPath sets the registered path for the handler.
	SetPath(p string)

	// Param returns path parameter by name.
	Param(name string) string

	// ParamNames returns path parameter names.
	ParamNames() []string

	// SetParamNames sets path parameter names.
	SetParamNames(names ...string)

	// ParamValues returns path parameter values.
	ParamValues() []string

	// SetParamValues sets path parameter values.
	SetParamValues(values ...string)

	// QueryParam returns the query param for the provided name.
	QueryParam(name string) string

	// QueryParams returns the query parameters as `url.Values`.
	QueryParams() url.Values

	// QueryString returns the URL query string.
	QueryString() string

	// FormValue returns the form field value for the provided name.
	FormValue(name string) string

	// FormParams returns the form parameters as `url.Values`.
	FormParams() (url.Values, error)

	// FormFile returns the multipart form file for the provided name.
	FormFile(name string) (*multipart.FileHeader, error)

	// MultipartForm returns the multipart form.
	MultipartForm() (*multipart.Form, error)

	// Cookie returns the named cookie provided in the request.
	Cookie(name string) (*http.Cookie, error)

	// SetCookie adds a `Set-Cookie` header in HTTP response.
	SetCookie(cookie *http.Cookie)

	// Cookies returns the HTTP cookies sent with the request.
	Cookies() []*http.Cookie

	// Get retrieves data from the context.
	Get(key string) interface{}

	// Set saves data in the context.
	Set(key string, val interface{})

	// Bind binds path params, query params and the request body into provided type `i`. The default binder
	// binds body based on Content-Type header.
	Bind(i interface{}) error

	// Validate validates provided `i`. It is usually called after `Context#Bind()`.
	// Validator must be registered using `Echo#Validator`.
	Validate(i interface{}) error

	// Render renders a template with data and sends a text/html response with status
	// code. Renderer must be registered using `Echo.Renderer`.
	Render(code int, name string, data interface{}) error

	// HTML sends an HTTP response with status code.
	HTML(code int, html string) error

	// HTMLBlob sends an HTTP blob response with status code.
	HTMLBlob(code int, b []byte) error

	// String sends a string response with status code.
	String(code int, s string) error

	// JSON sends a JSON response with status code.
	JSON(code int, i interface{}) error

	// JSONPretty sends a pretty-print JSON with status code.
	JSONPretty(code int, i interface{}, indent string) error

	// JSONBlob sends a JSON blob response with status code.
	JSONBlob(code int, b []byte) error

	// JSONP sends a JSONP response with status code. It uses `callback` to construct
	// the JSONP payload.
	JSONP(code int, callback string, i interface{}) error

	// JSONPBlob sends a JSONP blob response with status code. It uses `callback`
	// to construct the JSONP payload.
	JSONPBlob(code int, callback string, b []byte) error

	// XML sends an XML response with status code.
	XML(code int, i interface{}) error

	// XMLPretty sends a pretty-print XML with status code.
	XMLPretty(code int, i interface{}, indent string) error

	// XMLBlob sends an XML blob response with status code.
	XMLBlob(code int, b []byte) error

	// Blob sends a blob response with status code and content type.
	Blob(code int, contentType string, b []byte) error

	// Stream sends a streaming response with status code and content type.
	Stream(code int, contentType string, r io.Reader) error

	// File sends a response with the content of the file.
	File(file string) error

	// Attachment sends a response as attachment, prompting client to save the
	// file.
	Attachment(file string, name string) error

	// Inline sends a response as inline, opening the file in the browser.
	Inline(file string, name string) error

	// NoContent sends a response with no body and a status code.
	NoContent(code int) error

	// Redirect redirects the request to a provided URL with status code.
	Redirect(code int, url string) error

	// Error invokes the registered global HTTP error handler. Generally used by middleware.
	// A side-effect of calling global error handler is that now Response has been committed (sent to the client) and
	// middlewares up in chain can not change Response status code or Response body anymore.
	//
	// Avoid using this method in handlers as no middleware will be able to effectively handle errors after that.
	Error(err error)

	// Handler returns the matched handler by router.
	Handler() HandlerFunc

	// SetHandler sets the matched handler by router.
	SetHandler(h HandlerFunc)

	// Logger returns the `Logger` instance.
	Logger() Logger

	// SetLogger Set the logger
	SetLogger(l Logger)

	// Echo returns the `Echo` instance.
	Echo() *Echo

	// Reset resets the context after request completes. It must be called along
	// with `Echo#AcquireContext()` and `Echo#ReleaseContext()`.
	// See `Echo#ServeHTTP()`
	Reset(r *http.Request, w http.ResponseWriter)
}

type context struct {
	request  *http.Request
	response *Response
	query    url.Values
	echo     *Echo
	logger   Logger

	store Map
	lock  sync.RWMutex

	// following fields are set by Router

	// path is route path that Router matched. It is empty string where there is no route match.
	// Route registered with RouteNotFound is considered as a match and path therefore is not empty.
	path string

	// pnames length is tied to param count for the matched route
	pnames []string

	// Usually echo.Echo is sizing pvalues but there could be user created middlewares that decide to
	// overwrite parameter by calling SetParamNames + SetParamValues.
	// When echo.Echo allocated that slice it length/capacity is tied to echo.Echo.maxParam value.
	//
	// It is important that pvalues size is always equal or bigger to pnames length.
	pvalues []string
	handler HandlerFunc
}

const (
	// ContextKeyHeaderAllow is set by Router for getting value for `Allow` header in later stages of handler call chain.
	// Allow header is mandatory for status 405 (method not found) and useful for OPTIONS method requests.
	// It is added to context only when Router does not find matching method handler for request.
	ContextKeyHeaderAllow = "echo_header_allow"
)

const (
	defaultMemory = 32 << 20 // 32 MB
	indexPage     = "index.html"
	defaultIndent = "  "
)

func (c *context) writeContentType(value string) {
	header := c.Response().Header()
	if header.Get(HeaderContentType) == "" {
		header.Set(HeaderContentType, value)
	}
}

func (c *context) Request() *http.Request {
	return c.request
}

func (c *context) SetRequest(r *http.Request) {
	c.request = r
}

func (c *context) Response() *Response {
	return c.response
}

func (c *context) SetResponse(r *Response) {
	c.response = r
}

func (c *context) IsTLS() bool {
	return c.request.TLS != nil
}

func (c *context) IsWebSocket() bool {
	upgrade := c.request.Header.Get(HeaderUpgrade)
	return strings.EqualFold(upgrade, "websocket")
}

func (c *context) Scheme() string {
	// Can't use `r.Request.URL.Scheme`
	// See: https://groups.google.com/forum/#!topic/golang-nuts/pMUkBlQBDF0
	if c.IsTLS() {
		return "https"
	}
	if scheme := c.request.Header.Get(HeaderXForwardedProto); scheme != "" {
		return scheme
	}
	if scheme := c.request.Header.Get(HeaderXForwardedProtocol); scheme != "" {
		return scheme
	}
	if ssl := c.request.Header.Get(HeaderXForwardedSsl); ssl == "on" {
		return "https"
	}
	if scheme := c.request.Header.Get(HeaderXUrlScheme); scheme != "" {
		return scheme
	}
	return "http"
}

func (c *context) RealIP() string {
	if c.echo != nil && c.echo.IPExtractor != nil {
		return c.echo.IPExtractor(c.request)
	}
	// Fall back to legacy behavior
	if ip := c.request.Header.Get(HeaderXForwardedFor); ip != "" {
		i := strings.IndexAny(ip, ",")
		if i > 0 {
			xffip := strings.TrimSpace(ip[:i])
			xffip = strings.TrimPrefix(xffip, "[")
			xffip = strings.TrimSuffix(xffip, "]")
			return xffip
		}
		return ip
	}
	if ip := c.request.Header.Get(HeaderXRealIP); ip != "" {
		ip = strings.TrimPrefix(ip, "[")
		ip = strings.TrimSuffix(ip, "]")
		return ip
	}
	ra, _, _ := net.SplitHostPort(c.request.RemoteAddr)
	return ra
}

func (c *context) Path() string {
	return c.path
}

func (c *context) SetPath(p string) {
	c.path = p
}

func (c *context) Param(name string) string {
	for i, n := range c.pnames {
		if i < len(c.pvalues) {
			if n == name {
				return c.pvalues[i]
			}
		}
	}
	return ""
}

func (c *context) ParamNames() []string {
	return c.pnames
}

func (c *context) SetParamNames(names ...string) {
	c.pnames = names

	l := len(names)
	if len(c.pvalues) < l {
		// Keeping the old pvalues just for backward compatibility, but it sounds that doesn't make sense to keep them,
		// probably those values will be overridden in a Context#SetParamValues
		newPvalues := make([]string, l)
		copy(newPvalues, c.pvalues)
		c.pvalues = newPvalues
	}
}

func (c *context) ParamValues() []string {
	return c.pvalues[:len(c.pnames)]
}

func (c *context) SetParamValues(values ...string) {
	// NOTE: Don't just set c.pvalues = values, because it has to have length c.echo.maxParam (or bigger) at all times
	// It will brake the Router#Find code
	limit := len(values)
	if limit > len(c.pvalues) {
		c.pvalues = make([]string, limit)
	}
	for i := 0; i < limit; i++ {
		c.pvalues[i] = values[i]
	}
}

func (c *context) QueryParam(name string) string {
	if c.query == nil {
		c.query = c.request.URL.Query()
	}
	return c.query.Get(name)
}

func (c *context) QueryParams() url.Values {
	if c.query == nil {
		c.query = c.request.URL.Query()
	}
	return c.query
}

func (c *context) QueryString() string {
	return c.request.URL.RawQuery
}

func (c *context) FormValue(name string) string {
	return c.request.FormValue(name)
}

func (c *context) FormParams() (url.Values, error) {
	if strings.HasPrefix(c.request.Header.Get(HeaderContentType), MIMEMultipartForm) {
		if err := c.request.ParseMultipartForm(defaultMemory); err != nil {
			return nil, err
		}
	} else {
		if err := c.request.ParseForm(); err != nil {
			return nil, err
		}
	}
	return c.request.Form, nil
}

func (c *context) FormFile(name string) (*multipart.FileHeader, error) {
	f, fh, err := c.request.FormFile(name)
	if err != nil {
		return nil, err
	}
	f.Close()
	return fh, nil
}

func (c *context) MultipartForm() (*multipart.Form, error) {
	err := c.request.ParseMultipartForm(defaultMemory)
	return c.request.MultipartForm, err
}

func (c *context) Cookie(name string) (*http.Cookie, error) {
	return c.request.Cookie(name)
}

func (c *context) SetCookie(cookie *http.Cookie) {
	http.SetCookie(c.Response(), cookie)
}

func (c *context) Cookies() []*http.Cookie {
	return c.request.Cookies()
}

func (c *context) Get(key string) interface{} {
	c.lock.RLock()
	defer c.lock.RUnlock()
	return c.store[key]
}

func (c *context) Set(key string, val interface{}) {
	c.lock.Lock()
	defer c.lock.Unlock()

	if c.store == nil {
		c.store = make(Map)
	}
	c.store[key] = val
}

func (c *context) Bind(i interface{}) error {
	return c.echo.Binder.Bind(i, c)
}

func (c *context) Validate(i interface{}) error {
	if c.echo.Validator == nil {
		return ErrValidatorNotRegistered
	}
	return c.echo.Validator.Validate(i)
}

func (c *context) Render(code int, name string, data interface{}) (err error) {
	if c.echo.Renderer == nil {
		return ErrRendererNotRegistered
	}
	buf := new(bytes.Buffer)
	if err = c.echo.Renderer.Render(buf, name, data, c); err != nil {
		return
	}
	return c.HTMLBlob(code, buf.Bytes())
}

func (c *context) HTML(code int, html string) (err error) {
	return c.HTMLBlob(code, []byte(html))
}

func (c *context) HTMLBlob(code int, b []byte) (err error) {
	return c.Blob(code, MIMETextHTMLCharsetUTF8, b)
}

func (c *context) String(code int, s string) (err error) {
	return c.Blob(code, MIMETextPlainCharsetUTF8, []byte(s))
}

func (c *context) jsonPBlob(code int, callback string, i interface{}) (err error) {
	indent := ""
	if _, pretty := c.QueryParams()["pretty"]; c.echo.Debug || pretty {
		indent = defaultIndent
	}
	c.writeContentType(MIMEApplicationJavaScriptCharsetUTF8)
	c.response.WriteHeader(code)
	if _, err = c.response.Write([]byte(callback + "(")); err != nil {
		return
	}
	if err = c.echo.JSONSerializer.Serialize(c, i, indent); err != nil {
		return
	}
	if _, err = c.response.Write([]byte(");")); err != nil {
		return
	}
	return
}

func (c *context) json(code int, i interface{}, indent string) error {
	c.writeContentType(MIMEApplicationJSON)
	c.response.Status = code
	return c.echo.JSONSerializer.Serialize(c, i, indent)
}

func (c *context) JSON(code int, i interface{}) (err error) {
	indent := ""
	if _, pretty := c.QueryParams()["pretty"]; c.echo.Debug || pretty {
		indent = defaultIndent
	}
	return c.json(code, i, indent)
}

func (c *context) JSONPretty(code int, i interface{}, indent string) (err error) {
	return c.json(code, i, indent)
}

func (c *context) JSONBlob(code int, b []byte) (err error) {
	return c.Blob(code, MIMEApplicationJSON, b)
}

func (c *context) JSONP(code int, callback string, i interface{}) (err error) {
	return c.jsonPBlob(code, callback, i)
}

func (c *context) JSONPBlob(code int, callback string, b []byte) (err error) {
	c.writeContentType(MIMEApplicationJavaScriptCharsetUTF8)
	c.response.WriteHeader(code)
	if _, err = c.response.Write([]byte(callback + "(")); err != nil {
		return
	}
	if _, err = c.response.Write(b); err != nil {
		return
	}
	_, err = c.response.Write([]byte(");"))
	return
}

func (c *context) xml(code int, i interface{}, indent string) (err error) {
	c.writeContentType(MIMEApplicationXMLCharsetUTF8)
	c.response.WriteHeader(code)
	enc := xml.NewEncoder(c.response)
	if indent != "" {
		enc.Indent("", indent)
	}
	if _, err = c.response.Write([]byte(xml.Header)); err != nil {
		return
	}
	return enc.Encode(i)
}

func (c *context) XML(code int, i interface{}) (err error) {
	indent := ""
	if _, pretty := c.QueryParams()["pretty"]; c.echo.Debug || pretty {
		indent = defaultIndent
	}
	return c.xml(code, i, indent)
}

func (c *context) XMLPretty(code int, i interface{}, indent string) (err error) {
	return c.xml(code, i, indent)
}

func (c *context) XMLBlob(code int, b []byte) (err error) {
	c.writeContentType(MIMEApplicationXMLCharsetUTF8)
	c.response.WriteHeader(code)
	if _, err = c.response.Write([]byte(xml.Header)); err != nil {
		return
	}
	_, err = c.response.Write(b)
	return
}

func (c *context) Blob(code int, contentType string, b []byte) (err error) {
	c.writeContentType(contentType)
	c.response.WriteHeader(code)
	_, err = c.response.Write(b)
	return
}

func (c *context) Stream(code int, contentType string, r io.Reader) (err error) {
	c.writeContentType(contentType)
	c.response.WriteHeader(code)
	_, err = io.Copy(c.response, r)
	return
}

func (c *context) Attachment(file, name string) error {
	return c.contentDisposition(file, name, "attachment")
}

func (c *context) Inline(file, name string) error {
	return c.contentDisposition(file, name, "inline")
}

var quoteEscaper = strings.NewReplacer("\\", "\\\\", `"`, "\\\"")

func (c *context) contentDisposition(file, name, dispositionType string) error {
	c.response.Header().Set(HeaderContentDisposition, fmt.Sprintf(`%s; filename="%s"`, dispositionType, quoteEscaper.Replace(name)))
	return c.File(file)
}

func (c *context) NoContent(code int) error {
	c.response.WriteHeader(code)
	return nil
}

func (c *context) Redirect(code int, url string) error {
	if code < 300 || code > 308 {
		return ErrInvalidRedirectCode
	}
	c.response.Header().Set(HeaderLocation, url)
	c.response.WriteHeader(code)
	return nil
}

func (c *context) Error(err error) {
	c.echo.HTTPErrorHandler(err, c)
}

func (c *context) Echo() *Echo {
	return c.echo
}

func (c *context) Handler() HandlerFunc {
	return c.handler
}

func (c *context) SetHandler(h HandlerFunc) {
	c.handler = h
}

func (c *context) Logger() Logger {
	res := c.logger
	if res != nil {
		return res
	}
	return c.echo.Logger
}

func (c *context) SetLogger(l Logger) {
	c.logger = l
}

func (c *context) Reset(r *http.Request, w http.ResponseWriter) {
	c.request = r
	c.response.reset(w)
	c.query = nil
	c.handler = NotFoundHandler
	c.store = nil
	c.path = ""
	c.pnames = nil
	c.logger = nil
	// NOTE: Don't reset because it has to have length c.echo.maxParam (or bigger) at all times
	for i := 0; i < len(c.pvalues); i++ {
		c.pvalues[i] = ""
	}
}