context.go

package plum

import (
	"errors"
	"io"
	"math"
	"mime/multipart"
	"net"
	"net/http"
	"net/url"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"time"

	"github.com/go-plum/plum/binding"
	"github.com/go-plum/plum/render"
)

// abortIndex represents a typical value used in abort functions.
const abortIndex int8 = math.MaxInt8 >> 1

// Context is the most important part of plum.
// It allows us to pass variables between middleware,
// manage the flow,
// validate the JSON of a request and render a JSON response for example.
type Context struct {
	Request *http.Request
	Writer  http.ResponseWriter

	Params   Params
	handlers []HandlerFunc
	index    int8

	engine *Plum

	// This mutex protects Keys map.
	mu sync.RWMutex
	// Keys is a key/value pair exclusively for the context of each request.
	Keys map[string]any

	// SameSite allows a server to define a cookie attribute making it impossible for
	// the browser to send this cookie along with cross-site requests.
	sameSite http.SameSite
}

/************************************/
/********** CONTEXT CREATION ********/
/************************************/

func (c *Context) reset() {
	c.Params = c.Params[:0]
	c.handlers = nil
	c.index = -1
	c.Keys = nil
	c.sameSite = 0
}

// Copy returns a copy of the current context that can be safely used outside the request's scope.
// This has to be used when the context has to be passed to a goroutine.
func (c *Context) Copy() *Context {
	cp := Context{
		Request: c.Request,
		engine:  c.engine,
	}

	cp.index = abortIndex
	// cp.handlers = nil

	cKeys := c.Keys
	cp.Keys = make(map[string]any, len(cKeys))
	c.mu.RLock()
	for k, v := range cKeys {
		cp.Keys[k] = v
	}
	c.mu.RUnlock()

	cParams := c.Params
	cp.Params = make([]Param, len(cParams))
	copy(cp.Params, cParams)

	return &cp
}

// /************************************/
// /*********** FLOW CONTROL ***********/
// /************************************/

// Next should be used only inside middleware.
// It executes the pending handlers in the chain inside the calling handler.
// See example in GitHub.
func (c *Context) Next() {
	c.index++
	for c.index < int8(len(c.handlers)) {
		c.handlers[c.index](c)
		c.index++
	}
}

// IsAborted returns true if the current context was aborted.
func (c *Context) IsAborted() bool {
	return c.index >= abortIndex
}

// Abort prevents pending handlers from being called. Note that this will not stop the current handler.
// Let's say you have an authorization middleware that validates that the current request is authorized.
// If the authorization fails (ex: the password does not match), call Abort to ensure the remaining handlers
// for this request are not called.
func (c *Context) Abort() {
	c.index = abortIndex
}

// AbortWithStatus calls `Abort()` and writes the headers with the specified status code.
// For example, a failed attempt to authenticate a request could use: context.AbortWithStatus(401).
func (c *Context) AbortWithStatus(code int) {
	c.Status(code)
	c.Abort()
}

// AbortWithStatusJSON calls `Abort()` and then `JSON` internally.
// This method stops the chain, writes the status code and return a JSON body.
// It also sets the Content-Type as "application/json".
func (c *Context) AbortWithStatusJSON(code int, jsonObj any) {
	c.Abort()
	c.JSON(code, jsonObj)
}

/************************************/
/******** METADATA MANAGEMENT********/
/************************************/

// Set is used to store a new key/value pair exclusively for this context.
// It also lazy initializes  c.Keys if it was not used previously.
func (c *Context) Set(key string, value any) {
	c.mu.Lock()
	defer c.mu.Unlock()
	if c.Keys == nil {
		c.Keys = make(map[string]any)
	}

	c.Keys[key] = value
}

// Get returns the value for the given key, ie: (value, true).
// If the value does not exist it returns (nil, false)
func (c *Context) Get(key string) (value any, exists bool) {
	c.mu.RLock()
	defer c.mu.RUnlock()
	value, exists = c.Keys[key]
	return
}

/************************************/
/************ INPUT DATA ************/
/************************************/

// Param returns the value of the URL param.
// It is a shortcut for c.Params.ByName(key)
func (c *Context) Param(key string) string {
	return c.Params.ByName(key)
}

// AddParam adds param to context and
// replaces path param key with given value for e2e testing purposes
func (c *Context) AddParam(key, value string) {
	c.Params = append(c.Params, Param{Key: key, Value: value})
}

// Query returns the keyed url query value if it exists,
// otherwise it returns an empty string `("")`.
// It is shortcut for `c.Request.URL.Query().Get(key)`
func (c *Context) Query(key string) (value string) {
	value, _ = c.GetQuery(key)
	return
}

// DefaultQuery returns the keyed url query value if it exists,
// otherwise it returns the specified defaultValue string.
// See: Query() and GetQuery() for further information.
func (c *Context) DefaultQuery(key, defaultValue string) string {
	if value, ok := c.GetQuery(key); ok {
		return value
	}
	return defaultValue
}

// GetQuery is like Query(), it returns the keyed url query value
func (c *Context) GetQuery(key string) (string, bool) {
	if values, ok := c.GetQueryArray(key); ok {
		return values[0], ok
	}
	return "", false
}

// QueryArray returns a slice of strings for a given query key.
// The length of the slice depends on the number of params with the given key.
func (c *Context) QueryArray(key string) (values []string) {
	values, _ = c.GetQueryArray(key)
	return
}

func (c *Context) urlQuery() map[string][]string {
	if c.Request != nil {
		return c.Request.URL.Query()
	}
	return url.Values{}
}

// GetQueryArray returns a slice of strings for a given query key, plus
// a boolean value whether at least one value exists for the given key.
func (c *Context) GetQueryArray(key string) (values []string, ok bool) {
	values, ok = c.urlQuery()[key]
	return
}

// QueryMap returns a map for a given query key.
func (c *Context) QueryMap(key string) (dicts map[string]string) {
	dicts, _ = c.GetQueryMap(key)
	return
}

// GetQueryMap returns a map for a given query key, plus a boolean value
// whether at least one value exists for the given key.
func (c *Context) GetQueryMap(key string) (map[string]string, bool) {

	return c.get(c.urlQuery(), key)
}

// PostFormMap returns a map for a given form key.
func (c *Context) PostFormMap(key string) (dicts map[string]string) {
	dicts, _ = c.GetPostFormMap(key)
	return
}

// GetPostFormMap returns a map for a given form key, plus a boolean value
// whether at least one value exists for the given key.
func (c *Context) GetPostFormMap(key string) (map[string]string, bool) {
	return c.get(c.Request.PostForm, key)
}

// get is an internal method and returns a map which satisfies conditions.
func (c *Context) get(m map[string][]string, key string) (map[string]string, bool) {
	dicts := make(map[string]string)
	exist := false
	for k, v := range m {
		if i := strings.IndexByte(k, '['); i >= 1 && k[0:i] == key {
			if j := strings.IndexByte(k[i+1:], ']'); j >= 1 {
				exist = true
				dicts[k[i+1:][:j]] = v[0]
			}
		}
	}
	return dicts, exist
}

// FormFile returns the first file for the provided form key.
func (c *Context) FormFile(name string) (*multipart.FileHeader, error) {
	if c.Request.MultipartForm == nil {
		if err := c.Request.ParseMultipartForm(c.engine.opts.MaxMultipartMemory); err != nil {
			return nil, err
		}
	}
	f, fh, err := c.Request.FormFile(name)
	if err != nil {
		return nil, err
	}
	f.Close()
	return fh, err
}

// MultipartForm is the parsed multipart form, including file uploads.
func (c *Context) MultipartForm() (*multipart.Form, error) {
	err := c.Request.ParseMultipartForm(c.engine.opts.MaxMultipartMemory)
	return c.Request.MultipartForm, err
}

// SaveUploadedFile uploads the form file to specific dst.
func (c *Context) SaveUploadedFile(file *multipart.FileHeader, dst string) error {
	src, err := file.Open()
	if err != nil {
		return err
	}
	defer src.Close()

	if err = os.MkdirAll(filepath.Dir(dst), 0750); err != nil {
		return err
	}

	out, err := os.Create(dst)
	if err != nil {
		return err
	}
	defer out.Close()

	_, err = io.Copy(out, src)
	return err
}

// MustBindWith binds the passed struct pointer using the specified binding engine.
// It will abort the request with HTTP 400 if any error occurs.
// See the binding package.
func (c *Context) MustBindWith(obj any, b binding.Binding) error {
	if err := c.ShouldBindWith(obj, b); err != nil {
		c.AbortWithStatusJSON(http.StatusBadRequest, err)
		return err
	}
	return nil
}

// ShouldBindWith binds the passed struct pointer using the specified binding engine.
// See the binding package.
func (c *Context) ShouldBindWith(obj any, b binding.Binding) error {
	return b.Bind(c.Request, obj)
}

// ShouldBindBodyWith is similar with ShouldBindWith, but it stores the request
// body into the context, and reuse when it is called again.
//
// NOTE: This method reads the body before binding.
// bodyKey Keep non-repetition
func (c *Context) ShouldBindBodyWith(bodyKey string, obj any, bb binding.BindingBody) (err error) {
	var body []byte
	if cb, ok := c.Get(bodyKey); ok {
		if cbb, ok := cb.([]byte); ok {
			body = cbb
		}
	}
	if body == nil {
		body, err = io.ReadAll(c.Request.Body)
		if err != nil {
			return err
		}
		c.Set(bodyKey, body)
	}
	return bb.BindBody(body, obj)
}

// RemoteIP parses the IP from Request.RemoteAddr, normalizes and returns the IP (without the port).
func (c *Context) RemoteIP() string {
	ip, _, err := net.SplitHostPort(strings.TrimSpace(c.Request.RemoteAddr))
	if err != nil {
		return ""
	}
	return ip
}

func filterFlags(content string) string {
	for i, char := range content {
		if char == ' ' || char == ';' {
			return content[:i]
		}
	}
	return content
}

// ContentType returns the Content-Type header of the request.
func (c *Context) ContentType() string {
	return filterFlags(c.requestHeader("Content-Type"))
}

// IsWebsocket returns true if the request headers indicate that a websocket
// handshake is being initiated by the client.
func (c *Context) IsWebsocket() bool {
	if strings.Contains(strings.ToLower(c.requestHeader("Connection")), "upgrade") &&
		strings.EqualFold(c.requestHeader("Upgrade"), "websocket") {
		return true
	}
	return false
}

func (c *Context) requestHeader(key string) string {
	return c.Request.Header.Get(key)
}

/************************************/
/******** RESPONSE RENDERING ********/
/************************************/

// bodyAllowedForStatus is a copy of http.bodyAllowedForStatus non-exported function.
func bodyAllowedForStatus(status int) bool {
	switch {
	case status >= 100 && status <= 199:
		return false
	case status == http.StatusNoContent:
		return false
	case status == http.StatusNotModified:
		return false
	}
	return true
}

// Status sets the HTTP response code.
func (c *Context) Status(code int) {
	c.Writer.WriteHeader(code)
}

// Header is an intelligent shortcut for c.Writer.Header().Set(key, value).
// It writes a header in the response.
// If value == "", this method removes the header `c.Writer.Header().Del(key)`
func (c *Context) Header(key, value string) {
	if value == "" {
		c.Writer.Header().Del(key)
		return
	}
	c.Writer.Header().Set(key, value)
}

// GetHeader returns value from request headers.
func (c *Context) GetHeader(key string) string {
	return c.requestHeader(key)
}

// GetRawData returns stream data.
func (c *Context) GetRawData() ([]byte, error) {
	if c.Request.Body == nil {
		return nil, errors.New("cannot read nil body")
	}
	return io.ReadAll(c.Request.Body)
}

// SetSameSite with cookie
func (c *Context) SetSameSite(samesite http.SameSite) {
	c.sameSite = samesite
}

// SetCookie adds a Set-Cookie header to the ResponseWriter's headers.
// The provided cookie must have a valid Name. Invalid cookies may be
// silently dropped.
func (c *Context) SetCookie(name, value string, maxAge int, path, domain string, secure, httpOnly bool) {
	if path == "" {
		path = "/"
	}
	http.SetCookie(c.Writer, &http.Cookie{
		Name:     name,
		Value:    url.QueryEscape(value),
		MaxAge:   maxAge,
		Path:     path,
		Domain:   domain,
		SameSite: c.sameSite,
		Secure:   secure,
		HttpOnly: httpOnly,
	})
}

// Cookie returns the named cookie provided in the request or
// ErrNoCookie if not found. And return the named cookie is unescaped.
// If multiple cookies match the given name, only one cookie will
// be returned.
func (c *Context) Cookie(name string) (string, error) {
	cookie, err := c.Request.Cookie(name)
	if err != nil {
		return "", err
	}
	val, _ := url.QueryUnescape(cookie.Value)
	return val, nil
}

// Render writes the response headers and calls render.Render to render data.
func (c *Context) Render(code int, r render.Render) {
	c.Status(code)
	if !bodyAllowedForStatus(code) {
		r.WriteContentType(c.Writer)
		return
	}

	if err := r.Render(c.Writer); err != nil {
		// Pushing error to c.Errors
		c.engine.opts.Log.Error("Render error %+v", err)
		c.Abort()
	}
}

// HTML renders the HTTP template specified by its file name.
// It also updates the HTTP code and sets the Content-Type as "text/html".
// See http://golang.org/doc/articles/wiki/
func (c *Context) HTML(code int, name string, obj any) {
	instance := c.engine.opts.HTMLRender.Instance(name, obj)
	c.Render(code, instance)
}

// JSONP serializes the given struct as JSON into the response body.
// It adds padding to response body to request data from a server residing in a different domain than the client.
// It also sets the Content-Type as "application/javascript".
func (c *Context) JSONP(code int, obj any) {
	callback := c.DefaultQuery("callback", "")
	if callback == "" {
		c.Render(code, render.JSON{Data: obj})
		return
	}
	c.Render(code, render.JsonpJSON{Callback: callback, Data: obj})
}

// JSON serializes the given struct as JSON into the response body.
// It also sets the Content-Type as "application/json".
func (c *Context) JSON(code int, obj any) {
	c.Render(code, render.JSON{Data: obj})
}

// String writes the given string into the response body.
func (c *Context) String(code int, format string, values ...any) {
	c.Render(code, render.String{Format: format, Data: values})
}

// Redirect returns an HTTP redirect to the specific location.
func (c *Context) Redirect(code int, location string) {
	c.Render(-1, render.Redirect{
		Code:     code,
		Location: location,
		Request:  c.Request,
	})
}

// Data writes some data into the body stream and updates the HTTP code.
func (c *Context) Data(code int, contentType string, data []byte) {
	c.Render(code, render.Data{
		ContentType: contentType,
		Data:        data,
	})
}

// File writes the specified file into the body stream in an efficient way.
func (c *Context) File(filepath string) {
	http.ServeFile(c.Writer, c.Request, filepath)
}

// FileFromFS writes the specified file from http.FileSystem into the body stream in an efficient way.
func (c *Context) FileFromFS(filepath string, fs http.FileSystem) {
	defer func(old string) {
		c.Request.URL.Path = old
	}(c.Request.URL.Path)

	c.Request.URL.Path = filepath

	http.FileServer(fs).ServeHTTP(c.Writer, c.Request)
}

/************************************/
/***** GOLANG.ORG/X/NET/CONTEXT *****/
/************************************/

// hasRequestContext returns whether c.Request has Context and fallback.
func (c *Context) hasRequestContext() bool {
	hasRequestContext := c.Request != nil && c.Request.Context() != nil
	return hasRequestContext
}

// Deadline returns that there is no deadline (ok==false) when c.Request has no Context.
func (c *Context) Deadline() (deadline time.Time, ok bool) {
	if !c.hasRequestContext() {
		return
	}
	return c.Request.Context().Deadline()
}

// Done returns nil (chan which will wait forever) when c.Request has no Context.
func (c *Context) Done() <-chan struct{} {
	if !c.hasRequestContext() {
		return nil
	}
	return c.Request.Context().Done()
}

// Err returns nil when c.Request has no Context.
func (c *Context) Err() error {
	if !c.hasRequestContext() {
		return nil
	}
	return c.Request.Context().Err()
}

// Value returns the value associated with this context for key, or nil
// if no value is associated with key. Successive calls to Value with
// the same key returns the same result.
func (c *Context) Value(key any) any {
	if key == 0 {
		return c.Request
	}
	if keyAsString, ok := key.(string); ok {
		if val, exists := c.Get(keyAsString); exists {
			return val
		}
	}
	if !c.hasRequestContext() {
		return nil
	}
	return c.Request.Context().Value(key)
}