package api

import (
	"encoding/json"
	"errors"
	"fmt"
	"net/http"
	"strings"
	"time"

	"git.tilde.town/tildetown/bbj2/server/cmd/config"
	"git.tilde.town/tildetown/bbj2/server/cmd/db"
)

type HTTPError struct {
	Msg  string
	Code int
}

func (e *HTTPError) Error() string {
	return fmt.Sprintf("%d %s", e.Code, e.Msg)
}

func badMethod() error {
	return &HTTPError{Code: 400, Msg: "bad method"}
}

func invalidArgs(msg string) error {
	return &HTTPError{Code: 400, Msg: fmt.Sprintf("invalid args: %s", msg)}
}

type BBJResponse struct {
	Error   bool               `json:"error"`
	Data    interface{}        `json:"data"`
	Usermap map[string]db.User `json:"usermap"`
}

type APIHandler func() (*BBJResponse, error)

type API struct {
	User *db.User
	Opts config.Options
	Req  *http.Request
}

func NewAPI(opts config.Options, req *http.Request) (*API, error) {
	user, err := getUserFromReq(opts, req)
	if err != nil {
		return nil, &HTTPError{Msg: err.Error(), Code: 403}
	}
	return &API{
		Opts: opts,
		User: user,
		Req:  req,
	}, nil
}

func Invoke(w http.ResponseWriter, apiFn APIHandler) {
	resp, err := apiFn()
	if err != nil {
		he := &HTTPError{}
		_ = errors.As(err, &he)
		resp := BBJResponse{
			Error: true,
			Data:  he.Msg,
		}
		w.WriteHeader(he.Code)
		w.Header().Set("Content-Type", "application/json")
		json.NewEncoder(w).Encode(resp)
		return
	}
	w.WriteHeader(http.StatusOK)
	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(resp)
}

func getUserFromReq(opts config.Options, req *http.Request) (u *db.User, err error) {
	// TODO abstract sql stuff into db
	u = &db.User{}
	u.Username = req.Header.Get("User")
	u.Hash = req.Header.Get("Auth")
	if u.Username == "" || u.Username == "anon" {
		return
	}

	db := opts.DB
	stmt, err := db.Prepare("select auth_hash, id from users where user_name = ?")
	if err != nil {
		err = fmt.Errorf("db error: %w", err)
		return
	}
	defer stmt.Close()

	opts.Logger.Printf("querying for %s", u.Username)

	var authHash string
	if err = stmt.QueryRow(u.Username).Scan(&authHash, u.ID); err != nil {
		if strings.Contains(err.Error(), "no rows in result") {
			err = errors.New("no such user")
		} else {
			err = fmt.Errorf("db error: %w", err)
		}
	}

	if authHash != u.Hash {
		err = errors.New("bad credentials")
	}

	return
}

type instanceInfo struct {
	InstanceName string `json:"instance_name"`
	AllowAnon    bool   `json:"allow_anon"`
	Admins       []string
}

func (a *API) IsGet() bool {
	return a.Req.Method == "GET"
}

func (a *API) IsPost() bool {
	return a.Req.Method == "POST"
}

func (a *API) InstanceInfo() (resp *BBJResponse, err error) {
	if !a.IsGet() {
		err = badMethod()
		return
	}

	resp = &BBJResponse{
		Data: instanceInfo{
			InstanceName: a.Opts.Config.InstanceName,
			AllowAnon:    a.Opts.Config.AllowAnon,
			Admins:       a.Opts.Config.Admins,
		},
	}

	return
}

func (a *API) UserRegister() (resp *BBJResponse, err error) {
	if !a.IsPost() {
		err = badMethod()
		return
	}
	type AuthArgs struct {
		Username string `json:"user_name"`
		Hash     string `json:"auth_hash"`
	}

	var args AuthArgs
	if err = json.NewDecoder(a.Req.Body).Decode(&args); err != nil {
		err = invalidArgs(err.Error())
		return
	}

	if args.Hash == "" || args.Username == "" {
		err = invalidArgs(err.Error())
		return
	}

	if err = checkAuth(a.Opts, args.Username, args.Hash); err == nil {
		a.Opts.Logger.Printf("user %s already registered", args.Username)
		err = &HTTPError{Code: 403, Msg: "user already exists"}
		return
	} else if err.Error() != "no such user" {
		err = &HTTPError{Code: 500, Msg: err.Error()}
		return
	}

	u := db.User{
		Username: args.Username,
		Hash:     args.Hash,
		Created:  time.Now(), // TODO inject time
	}

	err = db.CreateUser(a.Opts.DB, u)

	return
}

func checkAuth(opts config.Options, username, hash string) (err error) {
	opts.Logger.Printf("querying for %s", username)
	var user *db.User
	if user, err = db.GetUserByName(opts.DB, username); err != nil {
		return
	}

	if user.Hash != hash {
		err = errors.New("bad credentials")
	}

	return
}