package jsFetch

import (
	"context"
	"errors"
	"io"
	"maps"
	"net"
	"runtime"
	"strconv"
	"strings"
	"sync"
	"time"
	"unicode"

	"crypto/tls"
	"mime/multipart"
	"net/url"
	"syscall/js"

	"git.ailur.dev/ailur/jsStreams"
)

// Transport is here only for compatibility with the Go standard library.
// All fields are ignored in fetch.
type Transport struct {
	// Proxy specifies a function to return a proxy for a given Request.
	// It is ignored in fetch.
	Proxy func(*Request) (*url.URL, error)

	// OnProxyError specifies a function to handle errors that occur while fetching a proxy.
	// It is ignored in fetch.
	OnProxyError func(*Request, *url.URL, error)

	// DialContext specifies the dial function for creating unencrypted TCP connections.
	// It is ignored in fetch.
	DialContext func(ctx context.Context, network, addr string) (net.Conn, error)

	// Dial specifies the dial function for creating unencrypted TCP connections.
	// It is ignored in fetch.
	Dial func(network, addr string) (net.Conn, error)

	// DialTLSContext specifies the dial function for creating TLS connections.
	// It is ignored in fetch.
	DialTLSContext func(ctx context.Context, network, addr string) (net.Conn, error)

	// DialTLS specifies the dial function for creating TLS connections.
	// It is ignored in fetch.
	DialTLS func(network, addr string) (net.Conn, error)

	// TLSClientConfig specifies the TLS configuration to use with tls.Client.
	// It is ignored in fetch.
	TLSClientConfig *tls.Config

	// TLSHandshakeTimeout specifies the maximum amount of time waiting to wait for a TLS handshake.
	// It is ignored in fetch.
	TLSHandshakeTimeout time.Duration

	// DisableKeepAlives specifies whether to disable keep-alive connections.
	// It is ignored in fetch.
	DisableKeepAlives bool

	// DisableCompression specifies whether to disable compression.
	// It is ignored in fetch.
	DisableCompression bool

	// MaxIdleConns specifies the maximum number of idle (keep-alive) connections to keep.
	// It is ignored in fetch.
	MaxIdleConns int

	// MaxIdleConnsPerHost specifies the maximum number of idle (keep-alive) connections to keep per host.
	// It is ignored in fetch.
	MaxIdleConnsPerHost int

	// IdleConnTimeout specifies the maximum amount of time an idle (keep-alive) connection will remain idle before closing itself.
	// It is ignored in fetch.
	IdleConnTimeout time.Duration

	// ResponseHeaderTimeout specifies the maximum amount of time to wait for a response header.
	// It is ignored in fetch.
	ResponseHeaderTimeout time.Duration

	// ExpectContinueTimeout specifies the maximum amount of time to wait for a 100-continue response.
	// It is ignored in fetch.
	ExpectContinueTimeout time.Duration

	// TLSNextProto specifies a function to upgrade the connection to a different protocol.
	// It is ignored in fetch.
	TLSNextProto map[string]func(authority string, c net.Conn) RoundTripper

	// ProxyConnectHeader specifies the headers to send to proxies during CONNECT requests.
	// It is ignored in fetch.
	ProxyConnectHeader Header

	// MaxResponseHeaderBytes specifies the maximum number of bytes to read from the server's response headers.
	// It is ignored in fetch.
	MaxResponseHeaderBytes int

	// WriteBufferSize specifies the size of the write buffer.
	// It is ignored in fetch.
	WriteBufferSize int

	// ReadBufferSize specifies the size of the read buffer.
	// It is ignored in fetch.
	ReadBufferSize int

	// ForceAttemptHTTP2 specifies whether to force an attempt to use HTTP/2.
	// It is ignored in fetch.
	ForceAttemptHTTP2 bool
}

// RoundTrip executes a single HTTP transaction, returning a Response for the provided Request.
// In the context of fetch, it will automatically follow redirects.
// This implementation is a wrapper around the fetch API.
func (t *Transport) RoundTrip(req *Request) (resp *Response, err error) {
	defer func() {
		recovery := recover()
		if recovery != nil {
			runtimeErr, ok := recovery.(runtime.Error)
			if ok {
				err = runtimeErr
			} else {
				err = errors.New(recovery.(string))
			}
		}
	}()

	if req.GetBody != nil {
		req.Body, err = req.GetBody()
		if err != nil {
			return nil, err
		}
	}
	headersMapStringInterface := make(map[string]interface{})
	for key, value := range req.Header {
		headersMapStringInterface[key] = value
	}
	if req.Body != nil {
		headersMapStringInterface["Content-Length"] = req.ContentLength
	}
	fetchArgs := map[string]interface{}{
		"method":  req.Method,
		"headers": headersMapStringInterface,
	}
	// Since all supported browsers are chromium based, lets just detect for chrome.
	// If we are, we can use a streamed client body
	if req.Method != "GET" && req.Method != "HEAD" && req.Body != nil {
		if !req.DisableStreamedClient {
			if !js.Global().Get("chrome").IsUndefined() {
				req.DisableStreamedClientChecks = true
			}
		}
		var jsBody js.Value
		if req.DisableStreamedClientChecks && !req.DisableStreamedClient {
			jsBody = jsStreams.ReaderToReadableStream(req.Body)
			fetchArgs["duplex"] = "half"
		} else {
			// Not today firefox, not today
			// Mozilla, please add support for streamed client bodies
			body, err := io.ReadAll(req.Body)
			if err != nil {
				return nil, err
			}
			jsBody = js.Global().Get("Uint8Array").New(len(body))
			js.CopyBytesToJS(jsBody, body)
		}
		fetchArgs["body"] = jsBody
	}
	promise := js.Global().Call("fetch", req.URL.String(), js.ValueOf(fetchArgs))

	var waitGroup sync.WaitGroup
	waitGroup.Add(1)

	promise.Call("then", js.FuncOf(func(this js.Value, args []js.Value) interface{} {
		resp = new(Response)
		resp.Request = req
		resp.Header = make(Header)
		args[0].Get("headers").Call("forEach", js.FuncOf(func(this js.Value, args []js.Value) interface{} {
			resp.Header.Set(args[0].String(), args[1].String())
			return nil
		}))
		resp.Status = args[0].Get("statusText").String()
		resp.StatusCode = args[0].Get("status").Int()
		if resp.Header.Has("Content-Length") {
			resp.ContentLength, err = strconv.ParseInt(resp.Header.Get("Content-Length"), 10, 64)
			if err != nil {
				resp.ContentLength = -1
			}
		}
		resp.Body = jsStreams.NewReadableStream(args[0].Get("body"))

		// Standard-library compatibility fields
		resp.Proto = "HTTP/1.1"
		resp.ProtoMajor = 1
		resp.ProtoMinor = 1
		resp.TransferEncoding = []string{"chunked"}
		resp.Trailer = make(Header)
		resp.TLS = nil
		resp.Close = false
		resp.Uncompressed = true

		waitGroup.Done()
		return nil
	}))

	promise.Call("catch", js.FuncOf(func(this js.Value, args []js.Value) interface{} {
		err = errors.New(args[0].Get("message").String())
		waitGroup.Done()
		return nil
	}))

	waitGroup.Wait()
	return
}

// Clone returns a copy of the Transport.
func (t *Transport) Clone() (newTransport *Transport) {
	newTransport = new(Transport)
	newTransport.Proxy = t.Proxy
	newTransport.OnProxyError = t.OnProxyError
	newTransport.DialContext = t.DialContext
	newTransport.Dial = t.Dial
	newTransport.DialTLSContext = t.DialTLSContext
	newTransport.DialTLS = t.DialTLS
	newTransport.TLSClientConfig = t.TLSClientConfig
	newTransport.TLSHandshakeTimeout = t.TLSHandshakeTimeout
	newTransport.DisableKeepAlives = t.DisableKeepAlives
	newTransport.DisableCompression = t.DisableCompression
	newTransport.MaxIdleConns = t.MaxIdleConns
	newTransport.MaxIdleConnsPerHost = t.MaxIdleConnsPerHost
	newTransport.IdleConnTimeout = t.IdleConnTimeout
	newTransport.ResponseHeaderTimeout = t.ResponseHeaderTimeout
	newTransport.ExpectContinueTimeout = t.ExpectContinueTimeout
	newTransport.TLSNextProto = t.TLSNextProto
	newTransport.ProxyConnectHeader = t.ProxyConnectHeader.Clone()
	newTransport.MaxResponseHeaderBytes = t.MaxResponseHeaderBytes
	newTransport.WriteBufferSize = t.WriteBufferSize
	newTransport.ReadBufferSize = t.ReadBufferSize
	newTransport.ForceAttemptHTTP2 = t.ForceAttemptHTTP2
	return
}

// CloseIdleConnections closes any idle connections.
// This does nothing in fetch.
func (t *Transport) CloseIdleConnections() {}

// RegisterProtocol registers a new protocol with a custom RoundTripper.
// This does nothing in fetch.
func (t *Transport) RegisterProtocol(protocol string, rt RoundTripper) {}

// FetchRoundTripper is a wrapper around the fetch API. It is used to make requests.
// It is the default RoundTripper used for this subset of net/http.
var FetchRoundTripper RoundTripper = &Transport{}

// RoundTripper is an interface representing the ability to execute a single HTTP transaction.
type RoundTripper interface {
	// RoundTrip executes a single HTTP transaction, returning a Response for the provided Request.
	// In the context of fetch, it will automatically follow redirects.
	RoundTrip(*Request) (*Response, error)
}

// Client is a fetch client. It is used to make requests.
type Client struct {
	// Transport specifies the mechanism by which individual requests are made.
	// If nil, FetchRoundTripper is used.
	Transport RoundTripper

	// Jar does nothing, but it is required for compatibility with the Go standard library.
	Jar CookieJar

	// Timeout specifies a time limit for requests made by this Client.
	Timeout time.Duration
}

// Do sends an HTTP request and returns an HTTP response, following policy (such as redirects, cookies, auth) as configured on the client.
func (c *Client) Do(req *Request) (resp *Response, err error) {
	if c.Transport == nil {
		c.Transport = FetchRoundTripper
	}
	return c.Transport.RoundTrip(req)
}

// CookieJar does nothing, but it is required for compatibility with the Go standard library.
type CookieJar interface {
	SetCookies(u *url.URL, cookies []*Cookie)
	Cookies(u *url.URL) []*Cookie
}

// SameSite does nothing, but it is required for compatibility with the Go standard library.
type SameSite int

// Cookie does nothing, but it is required for compatibility with the Go standard library.
type Cookie struct {
	Name        string
	Value       string
	Quoted      bool
	Path        string
	Domain      string
	Expires     time.Time
	RawExpires  string
	MaxAge      int
	Secure      bool
	HttpOnly    bool
	SameSite    SameSite
	Partitioned bool
	Raw         string
	Unparsed    []string
}

// Fetch is a fetch client. It is used to make requests.
// It wraps around JS fetch.
var Fetch = &Client{
	Transport: FetchRoundTripper,
	Timeout:   20 * time.Second,
}

// DefaultClient is an alias for Fetch.
var DefaultClient = Fetch

func CanonicalHeaderKey(key string) string {
	const allowedCharacters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789!#$%&'*+-.^_`|~"
	for _, char := range []rune(key) {
		if !strings.Contains(allowedCharacters, string(char)) {
			return key
		}
	}
	splitStrings := strings.Split(key, "-")
	for splitString, _ := range splitStrings {
		var stringBuilder strings.Builder
		stringBuilder.WriteRune(unicode.ToUpper([]rune(splitStrings[splitString])[0]))
		stringBuilder.WriteString(strings.ToLower(splitStrings[splitString][1:]))
		splitStrings[splitString] = stringBuilder.String()
	}
	return strings.Join(splitStrings, "-")
}

type Header map[string]string

func (h Header) Add(key, value string) {
	h[CanonicalHeaderKey(key)] = value
}

func (h Header) Clone() (newHeader Header) {
	maps.Copy(h, newHeader)
	return
}

func (h Header) Del(key string) {
	delete(h, CanonicalHeaderKey(key))
}

func (h Header) Get(key string) (value string) {
	value, _ = h[CanonicalHeaderKey(key)]
	return
}

func (h Header) Set(key, value string) {
	h[CanonicalHeaderKey(key)] = value
}

func (h Header) Has(key string) (has bool) {
	_, has = h[CanonicalHeaderKey(key)]
	return
}

func (h Header) Values() (values []string) {
	for _, value := range h {
		values = append(values, value)
	}
	return
}

func (h Header) Write(w io.Writer) error {
	for key, value := range h {
		_, err := w.Write([]byte(key + ": " + value + "\r\n"))
		if err != nil {
			return err
		}
	}
	return nil
}

func (h Header) WriteSubset(w io.Writer, exclude map[string]bool) error {
	for key, value := range h {
		excludeKey, _ := exclude[key]
		if excludeKey {
			continue
		}
		_, err := w.Write([]byte(key + ": " + value + "\r\n"))
		if err != nil {
			return err
		}
	}
	return nil
}

type Request struct {
	// DisableStreamedClient specifies whether to use a streamed client body.
	// This is set to false by default, but has checks to make sure it's running on a supported browser.
	// HTTP/2 or QUIC to be enabled when using V8, which is not always the case, particularly on
	// older servers or test servers.
	//
	// If DisableStreamedClientChecks is set to false, the client will first attempt to detect if
	// the server supports HTTP/2 or QUIC and if you are running a supported JavaScript engine.
	// Supported browser engines include:
	// - V8 (Chrome, Edge, Opera)
	// Unsupported browser engines include:
	// - SpiderMonkey (Firefox)
	// - JavaScriptCore (Safari)
	// - Chakra (Internet Explorer)
	// - KJS (Konqueror)
	// - Presto (Opera Mini and ancient versions of Opera)
	// Data from https://caniuse.com/mdn-api_request_request_request_body_readablestream
	// TL;DR If it's chromium it'll work.
	DisableStreamedClient bool

	// DisableStreamedClientChecks specifies whether to disable checks for streamed clients.
	// It does nothing if UseStreamedClient is set to false.
	// Having it set to false may add another HEAD request to the server, which may be undesirable.
	// Also, forcing it on may be useful if SpiderMonkey one day supports streamed clients bodies.
	DisableStreamedClientChecks bool

	// Method specifies the HTTP method (GET, POST, PUT, etc.).
	Method string

	// URL specifies either the URL to fetch as a string, or a URL object.
	URL *url.URL

	// Headers is a Headers object, allowing you to set request headers.
	Header Header

	// Body is an optional body to be sent with the request.
	Body io.ReadCloser

	// GetBody is an optional function that returns a ReadCloser for the body.
	GetBody func() (io.ReadCloser, error)

	// ContentLength is the length of the body. It is mostly superseded by the Content-Length header.
	ContentLength int64

	// The following fields are not used by fetch and exist mostly for compatibility with the Go standard library.
	// They will do nothing. Do not use them.

	// Proto, ProtoMajor, ProtoMinor specify the HTTP protocol version.
	// This is useless, as fetch does not allow you to specify the protocol version.
	Proto      string
	ProtoMajor int
	ProtoMinor int

	// Close indicates whether to close the connection after the request.
	// This is useless, as fetch does not allow you to specify whether to close the connection and instead forces you to use a WebSocket.
	Close bool

	// Host specifies the host to perform the request to.
	// This is useless, as it only makes sense in the context of the Host or :authority headers, both of which are filled-in automatically by fetch.
	Host string

	// TransferEncoding specifies the transfer encodings to be used.
	// This is useless, as since we always use a stream, the transfer encoding is always chunked.
	TransferEncoding []string

	// Form, PostForm, and MultipartForm specify the parsed form data.
	// This is useless, because even the Go standard library does not use it.
	// Use Body instead.
	Form          url.Values
	PostForm      url.Values
	MultipartForm *url.Values

	// Trailer specifies additional headers that are sent after the request body.
	// This is useless, as fetch does not allow you to specify trailers.
	// Not to mention, nothing supports trailers.
	Trailer Header

	// RemoteAddr and RequestURI specify the remote address and Request-URI for the request.
	// This is useless, as fetch does not allow you to specify the remote address, and you should use URL instead of RequestURI.
	RemoteAddr string
	RequestURI string

	// TLS allows you to specify the TLS connection state.
	// This is useless, as fetch does not allow you to specify the TLS connection state.
	TLS *tls.ConnectionState

	// Cancel is an optional channel that can be used to cancel the request.
	// This isn't even in the Go standard library anymore.
	Cancel <-chan struct{}

	// Response is the response that caused this request to be created, usually in a redirect.
	// This is useless, as fetch follows redirects automatically.
	Response *Response

	// Pattern is the pattern that was matched for this request.
	// This is useless, as fetch does not support pattern matching.
	Pattern string
}

// AddCookie does nothing, but it is required for compatibility with the Go standard library.
func (r *Request) AddCookie(c *Cookie) {}

// BasicAuth does nothing, but it is required for compatibility with the Go standard library.
func (r *Request) BasicAuth() (username, password string, ok bool) { return }

func (r *Request) Clone() (newRequest *Request) {
	newRequest = new(Request)
	newRequest.Method = r.Method
	newRequest.URL = r.URL
	newRequest.Header = r.Header.Clone()
	newRequest.Body = r.Body
	newRequest.GetBody = r.GetBody
	newRequest.ContentLength = r.ContentLength
	newRequest.TransferEncoding = r.TransferEncoding
	newRequest.Proto = r.Proto
	newRequest.ProtoMajor = r.ProtoMajor
	newRequest.ProtoMinor = r.ProtoMinor
	newRequest.Close = r.Close
	newRequest.Host = r.Host
	newRequest.Form = r.Form
	newRequest.PostForm = r.PostForm
	newRequest.MultipartForm = r.MultipartForm
	newRequest.Trailer = r.Trailer.Clone()
	newRequest.RemoteAddr = r.RemoteAddr
	newRequest.RequestURI = r.RequestURI
	newRequest.TLS = r.TLS
	newRequest.Cancel = r.Cancel
	newRequest.Response = r.Response
	newRequest.Pattern = r.Pattern
	return
}

// Context does nothing, but it is required for compatibility with the Go standard library.
func (r *Request) Context() context.Context { return context.Background() }

// Cookie does nothing, but it is required for compatibility with the Go standard library.
func (r *Request) Cookie(name string) (*Cookie, error) { return nil, nil }

// Cookies does nothing, but it is required for compatibility with the Go standard library.
func (r *Request) Cookies() []*Cookie { return nil }

// CookiesNamed does nothing, but it is required for compatibility with the Go standard library.
func (r *Request) CookiesNamed(name string) []*Cookie { return nil }

// FormFile does nothing, but it is required for compatibility with the Go standard library.
func (r *Request) FormFile(key string) (multipart.File, *multipart.FileHeader, error) {
	return nil, nil, nil
}

// FormValue does nothing, but it is required for compatibility with the Go standard library.
func (r *Request) FormValue(key string) string { return "" }

// MultipartReader does nothing, but it is required for compatibility with the Go standard library.
func (r *Request) MultipartReader() (*multipart.Reader, error) { return nil, nil }

// ParseForm does nothing, but it is required for compatibility with the Go standard library.
func (r *Request) ParseForm() error { return nil }

// ParseMultipartForm does nothing, but it is required for compatibility with the Go standard library.
func (r *Request) ParseMultipartForm(maxMemory int64) error { return nil }

// PostFormValue does nothing, but it is required for compatibility with the Go standard library.
func (r *Request) PostFormValue(key string) string { return "" }

// ProtoAtLeast does nothing, but it is required for compatibility with the Go standard library.
func (r *Request) ProtoAtLeast(major, minor int) bool { return false }

// Finally, something that does something!

// Referer returns the value of the Referer header.
func (r *Request) Referer() string {
	return r.Header.Get("Referer")
}

// SetBasicAuth does nothing, but it is required for compatibility with the Go standard library.
func (r *Request) SetBasicAuth(username, password string) {}

// UserAgent returns the value of the User-Agent header.
func (r *Request) UserAgent() string {
	return r.Header.Get("User-Agent")
}

// WithContext does nothing, but it is required for compatibility with the Go standard library.
func (r *Request) WithContext(ctx context.Context) *Request { return r }

// Write writes an HTTP/1.1 request, which is the header and body, in wire format.
// It is not yet implemented (and probably never will be, because after all, why would you need to write an HTTP request in wire format?).
func (r *Request) Write(w io.Writer) error { return errors.New("not implemented") }

// WriteProxy does nothing, but it is required for compatibility with the Go standard library.
func (r *Request) WriteProxy(w io.Writer) error { return nil }

func NewRequest(method, uri string, body io.Reader) (request *Request, err error) {
	request = new(Request)
	request.Method = method
	request.URL, err = url.Parse(uri)
	if err != nil {
		return
	}
	request.Header = make(Header)
	request.Body = io.NopCloser(body)
	return
}

type Response struct {
	// Status specifies the HTTP status.
	// It will be an empty string if using HTTP/2.
	Status string

	// StatusCode specifies the HTTP status code.
	StatusCode int

	// Header specifies the response headers.
	Header Header

	// Body is the response body.
	Body io.ReadCloser

	// TransferEncoding specifies the transfer encodings that have been applied to the response.
	TransferEncoding []string

	// ContentLength specifies the length of the body.
	// It is mostly superseded by the Content-Length header.
	// A value of -1 indicates that the length is unknown.
	ContentLength int64

	// Request is the request that was made to get this response.
	Request *Request

	// The following fields are not used by fetch and exist mostly for compatibility with the Go standard library.
	// They will do nothing. Do not use them.

	// Proto, ProtoMajor, ProtoMinor specify the HTTP protocol version.
	// This is useless, as fetch does not allow you to specify the protocol version.
	Proto      string
	ProtoMajor int
	ProtoMinor int

	// Close indicates whether to close the connection after the request.
	// This is useless, as fetch does not allow you to specify whether to close the connection and instead forces you to use a WebSocket.
	Close bool

	// Uncompressed specifies whether the response is uncompressed.
	// This is useless, as fetch does not allow you to specify whether the response is uncompressed.
	Uncompressed bool

	// Trailer specifies additional headers that are sent after the request body.
	// This is useless, as fetch does not allow you to specify trailers.
	// Not to mention, nothing supports trailers.
	Trailer Header

	// TLS allows you to specify the TLS connection state.
	// This is useless, as fetch does not allow you to specify the TLS connection state.
	TLS *tls.ConnectionState
}

func Get(url string) (response *Response, err error) {
	request, err := NewRequest("GET", url, nil)
	if err != nil {
		return
	}
	response, err = Fetch.Do(request)
	return
}

func Post(url string, contentType string, body io.Reader) (response *Response, err error) {
	request, err := NewRequest("POST", url, body)
	if err != nil {
		return
	}
	request.Header.Add("Content-Type", contentType)
	response, err = Fetch.Do(request)
	return
}

func PostForm(url string, data url.Values) (response *Response, err error) {
	body := io.NopCloser(strings.NewReader(data.Encode()))
	request, err := NewRequest("POST", url, body)
	if err != nil {
		return
	}
	request.Header.Add("Content-Type", "application/x-www-form-urlencoded")
	response, err = Fetch.Do(request)
	return
}

// Cookies does nothing, but it is required for compatibility with the Go standard library.
func (r *Response) Cookies() []*Cookie { return nil }

// Location returns the location header (if present).
func (r *Response) Location() (string, error) {
	if r.Header.Has("Location") {
		return r.Header.Get("Location"), nil
	} else {
		return "", errors.New("http: no Location header in response")
	}
}

// ProtoAtLeast does nothing, but it is required for compatibility with the Go standard library.
func (r *Response) ProtoAtLeast(major, minor int) bool { return true }

// Write writes an HTTP/1.1 response, which is the header and body, in wire format.
// It is not yet implemented (and probably never will be, because after all, why would you need to write an HTTP response in wire format?).
func (r *Response) Write(w io.Writer) error { return nil }