package ibd

import (
	"bytes"
	"context"
	"encoding/base64"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"strings"

	"github.com/ansg191/ibd-trader-backend/internal/ibd/transport"
	"golang.org/x/net/html"
)

const (
	signInUrl       = "https://myibd.investors.com/secure/signin.aspx?eurl=https%3A%2F%2Fwww.investors.com"
	authenticateUrl = "https://sso.accounts.dowjones.com/authenticate"
	postAuthUrl     = "https://sso.accounts.dowjones.com/postauth/handler"
	cookieName      = ".ASPXAUTH"
)

var ErrAuthCookieNotFound = errors.New("cookie not found")
var ErrBadCredentials = errors.New("bad credentials")

func (c *Client) Authenticate(
	ctx context.Context,
	username,
	password string,
) (*http.Cookie, error) {
	cfg, err := c.getLoginPage(ctx)
	if err != nil {
		return nil, err
	}

	token, params, err := c.sendAuthRequest(ctx, cfg, username, password)
	if err != nil {
		return nil, err
	}

	return c.sendPostAuth(ctx, token, params)
}

func (c *Client) getLoginPage(ctx context.Context) (*authConfig, error) {
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, signInUrl, nil)
	if err != nil {
		return nil, err
	}

	resp, err := c.Do(req, withRequiredProps(transport.PropertiesReliable))
	if err != nil {
		return nil, err
	}
	defer func(Body io.ReadCloser) {
		_ = Body.Close()
	}(resp.Body)

	if resp.StatusCode != http.StatusOK {
		content, err := io.ReadAll(resp.Body)
		if err != nil {
			return nil, fmt.Errorf("failed to read response body: %w", err)
		}
		return nil, fmt.Errorf(
			"unexpected status code %d: %s",
			resp.StatusCode,
			string(content),
		)
	}

	node, err := html.Parse(resp.Body)
	if err != nil {
		return nil, err
	}

	cfg, err := extractAuthConfig(node)
	if err != nil {
		return nil, fmt.Errorf("failed to extract auth config: %w", err)
	}

	return cfg, nil
}

func (c *Client) sendAuthRequest(ctx context.Context, cfg *authConfig, username, password string) (string, string, error) {
	body := authRequestBody{
		ClientId:     cfg.ClientID,
		RedirectUri:  cfg.CallbackURL,
		Tenant:       "sso",
		ResponseType: cfg.ExtraParams.ResponseType,
		Username:     username,
		Password:     password,
		Scope:        cfg.ExtraParams.Scope,
		State:        cfg.ExtraParams.State,
		Headers: struct {
			XRemoteUser string `json:"x-_remote-_user"`
		}(struct{ XRemoteUser string }{
			XRemoteUser: username,
		}),
		XOidcProvider: "localop",
		Protocol:      cfg.ExtraParams.Protocol,
		Nonce:         cfg.ExtraParams.Nonce,
		UiLocales:     cfg.ExtraParams.UiLocales,
		Csrf:          cfg.ExtraParams.Csrf,
		Intstate:      cfg.ExtraParams.Intstate,
		Connection:    "DJldap",
	}
	bodyJson, err := json.Marshal(body)
	if err != nil {
		return "", "", fmt.Errorf("failed to marshal auth request body: %w", err)
	}

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, authenticateUrl, bytes.NewReader(bodyJson))
	if err != nil {
		return "", "", err
	}

	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Auth0-Client", "eyJuYW1lIjoiYXV0aDAuanMtdWxwIiwidmVyc2lvbiI6IjkuMjQuMSJ9")

	resp, err := c.Do(req,
		withRequiredProps(transport.PropertiesReliable),
		withExpectedStatuses(http.StatusOK, http.StatusUnauthorized))
	if err != nil {
		return "", "", err
	}
	defer func(Body io.ReadCloser) {
		_ = Body.Close()
	}(resp.Body)

	if resp.StatusCode == http.StatusUnauthorized {
		return "", "", ErrBadCredentials
	} else if resp.StatusCode != http.StatusOK {
		content, err := io.ReadAll(resp.Body)
		if err != nil {
			return "", "", fmt.Errorf("failed to read response body: %w", err)
		}
		return "", "", fmt.Errorf(
			"unexpected status code %d: %s",
			resp.StatusCode,
			string(content),
		)
	}

	node, err := html.Parse(resp.Body)
	if err != nil {
		return "", "", err
	}

	return extractTokenParams(node)
}

func (c *Client) sendPostAuth(ctx context.Context, token, params string) (*http.Cookie, error) {
	body := fmt.Sprintf("token=%s&params=%s", token, params)
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, postAuthUrl, strings.NewReader(body))
	if err != nil {
		return nil, err
	}

	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")

	resp, err := c.Do(req, withRequiredProps(transport.PropertiesReliable))
	if err != nil {
		return nil, err
	}
	defer func(Body io.ReadCloser) {
		_ = Body.Close()
	}(resp.Body)

	if resp.StatusCode != http.StatusOK {
		content, err := io.ReadAll(resp.Body)
		if err != nil {
			return nil, fmt.Errorf("failed to read response body: %w", err)
		}
		return nil, fmt.Errorf(
			"unexpected status code %d: %s",
			resp.StatusCode,
			string(content),
		)
	}

	// Extract cookie
	for _, cookie := range resp.Cookies() {
		if cookie.Name == cookieName {
			return cookie, nil
		}
	}

	return nil, ErrAuthCookieNotFound
}

func extractAuthConfig(node *html.Node) (*authConfig, error) {
	// Find `root` element
	root := findId(node, "root")
	if root == nil {
		return nil, fmt.Errorf("root element not found")
	}

	// Get adjacent script element
	var script *html.Node
	for s := root.NextSibling; s != nil; s = s.NextSibling {
		if s.Type == html.ElementNode && s.Data == "script" {
			script = s
			break
		}
	}

	if script == nil {
		return nil, fmt.Errorf("script element not found")
	}

	// Get script content
	content := extractText(script)

	// Find `AUTH_CONFIG` variable
	const authConfigVar = "const AUTH_CONFIG = '"
	i := strings.Index(content, authConfigVar)
	if i == -1 {
		return nil, fmt.Errorf("AUTH_CONFIG not found")
	}

	// Find end of `AUTH_CONFIG` variable
	j := strings.Index(content[i+len(authConfigVar):], "'")

	// Extract `AUTH_CONFIG` value
	authConfigJSONB64 := content[i+len(authConfigVar) : i+len(authConfigVar)+j]

	// Decode `AUTH_CONFIG` value
	authConfigJSON, err := base64.StdEncoding.DecodeString(authConfigJSONB64)
	if err != nil {
		return nil, fmt.Errorf("failed to decode AUTH_CONFIG: %w", err)
	}

	// Unmarshal `AUTH_CONFIG` value
	var cfg authConfig
	if err = json.Unmarshal(authConfigJSON, &cfg); err != nil {
		return nil, fmt.Errorf("failed to unmarshal AUTH_CONFIG: %w", err)
	}

	return &cfg, nil
}

type authConfig struct {
	Auth0Domain string `json:"auth0Domain"`
	CallbackURL string `json:"callbackURL"`
	ClientID    string `json:"clientID"`
	ExtraParams struct {
		Protocol     string `json:"protocol"`
		Scope        string `json:"scope"`
		ResponseType string `json:"response_type"`
		Nonce        string `json:"nonce"`
		UiLocales    string `json:"ui_locales"`
		Csrf         string `json:"_csrf"`
		Intstate     string `json:"_intstate"`
		State        string `json:"state"`
	} `json:"extraParams"`
	InternalOptions struct {
		ResponseType string `json:"response_type"`
		ClientId     string `json:"client_id"`
		Scope        string `json:"scope"`
		RedirectUri  string `json:"redirect_uri"`
		UiLocales    string `json:"ui_locales"`
		Eurl         string `json:"eurl"`
		Nonce        string `json:"nonce"`
		State        string `json:"state"`
		Resource     string `json:"resource"`
		Protocol     string `json:"protocol"`
		Client       string `json:"client"`
	} `json:"internalOptions"`
	IsThirdPartyClient  bool `json:"isThirdPartyClient"`
	AuthorizationServer struct {
		Url    string `json:"url"`
		Issuer string `json:"issuer"`
	} `json:"authorizationServer"`
}

func extractTokenParams(node *html.Node) (token string, params string, err error) {
	inputs := findChildrenRecursive(node, func(node *html.Node) bool {
		return node.Type == html.ElementNode && node.Data == "input"
	})

	var tokenNode, paramsNode *html.Node
	for _, input := range inputs {
		for _, attr := range input.Attr {
			if attr.Key == "name" && attr.Val == "token" {
				tokenNode = input
			} else if attr.Key == "name" && attr.Val == "params" {
				paramsNode = input
			}
		}
	}

	if tokenNode == nil {
		return "", "", fmt.Errorf("token input not found")
	}
	if paramsNode == nil {
		return "", "", fmt.Errorf("params input not found")
	}

	for _, attr := range tokenNode.Attr {
		if attr.Key == "value" {
			token = attr.Val
		}
	}
	for _, attr := range paramsNode.Attr {
		if attr.Key == "value" {
			params = attr.Val
		}
	}

	return
}

type authRequestBody struct {
	ClientId     string `json:"client_id"`
	RedirectUri  string `json:"redirect_uri"`
	Tenant       string `json:"tenant"`
	ResponseType string `json:"response_type"`
	Username     string `json:"username"`
	Password     string `json:"password"`
	Scope        string `json:"scope"`
	State        string `json:"state"`
	Headers      struct {
		XRemoteUser string `json:"x-_remote-_user"`
	} `json:"headers"`
	XOidcProvider string `json:"x-_oidc-_provider"`
	Protocol      string `json:"protocol"`
	Nonce         string `json:"nonce"`
	UiLocales     string `json:"ui_locales"`
	Csrf          string `json:"_csrf"`
	Intstate      string `json:"_intstate"`
	Connection    string `json:"connection"`
}