package auth

import (
	"crypto/rand"
	"encoding/hex"
	"net/http"
	"strings"
	"time"

	"github.com/labstack/echo/v4"
)

type FlowStore map[FlowID]*Flow

type FlowRequest struct {
	ClientID    string    `json:"client_id"`
	Handler     []*string `json:"handler"`
	RedirectURI string    `json:"redirect_uri"`
}

type FlowSchemaItem struct {
	Type     string `json:"type"`
	Name     string `json:"name"`
	Required bool   `json:"required"`
}

type FlowType string

const (
	TypeForm FlowType = "form"
)

type FlowID string
type Step string

const (
	StepInit Step = "init"
)

type Flow struct {
	Type      FlowType         `json:"type"`
	ID        FlowID           `json:"flow_id"`
	Handler   []*string        `json:"handler"`
	StepID    Step             `json:"step_id"`
	Schema    []FlowSchemaItem `json:"data_schema"`
	Errors    interface{}      `json:"errors"`
	DescPlace *string          `json:"description_placeholders"`
	LastStep  *string          `json:"last_step"`

	request *FlowRequest
	age     time.Time
}

func (f *Flow) touch() {
	f.age = time.Now()
}

func genFlowID() FlowID {
	b := make([]byte, 16)
	if _, err := rand.Read(b); err != nil {
		panic(err)
	}

	return FlowID(hex.EncodeToString(b))
}

func (fs FlowStore) register(f *Flow) {
	fs.cull()
	fs[f.ID] = f
}

func (fs FlowStore) Remove(f *Flow) {
	delete(fs, f.ID)
}

const cullAge = time.Minute * 30

func (fs FlowStore) cull() {
	for k, v := range fs {
		if time.Now().Sub(v.age) > cullAge {
			delete(fs, k)
		}
	}
}

func (fs FlowStore) Get(id FlowID) *Flow {
	f, ok := fs[id]
	if ok {
		return f
	}

	return nil
}

func (a *Authenticator) NewFlow(r *FlowRequest) *Flow {
	var sch []FlowSchemaItem

	for _, h := range r.Handler {
		if h == nil {
			break
		}

		if hand := a.Provider(*h); hand != nil {
			sch = hand.FlowSchema()
			break
		}
	}

	if sch == nil {
		return nil
	}

	flow := &Flow{
		Type:    TypeForm,
		ID:      genFlowID(),
		StepID:  StepInit,
		Schema:  sch,
		Handler: r.Handler,
		Errors:  []string{},
		request: r,
	}
	flow.touch()

	a.Flows.register(flow)

	return flow
}

func (f *Flow) progress(a *Authenticator, c echo.Context) error {
	switch f.StepID {
	case StepInit:
		rm := make(map[string]interface{})

		err := c.Bind(&rm)
		if err != nil {
			return c.String(http.StatusBadRequest, err.Error())
		}

		for _, si := range f.Schema {
			if si.Required {
				if _, ok := rm[si.Name]; !ok {
					return c.String(http.StatusBadRequest, "missing required param "+si.Name)
				}
			}
		}
		err = a.Check(f, rm)
		switch err {
		case nil:
			// TODO: setup the session. delete the flow.
			a.Flows.Remove(f)
			return c.String(http.StatusOK, "login success!")
		case ErrInvalidHandler:
			return c.String(http.StatusNotFound, err.Error())
		case ErrInvalidAuth:
			fallthrough
		default:
			f.Errors = map[string]interface{}{
				"base": "invalid_auth",
			}
			return c.JSON(http.StatusOK, f)
		}
	default:
		return c.String(http.StatusBadRequest, "unknown flow step")
	}
}

func (a *Authenticator) LoginFlowDeleteHandler(c echo.Context) error {
	flowID := c.Param("flow_id")

	if flowID == "" {
		return c.String(http.StatusBadRequest, "empty flow ID")
	}

	delete(a.Flows, FlowID(flowID))

	return c.String(http.StatusOK, "deleted")
}

func setJSON(c echo.Context) {
	if c.Request().Method == http.MethodPost && strings.HasPrefix(c.Request().Header.Get(echo.HeaderContentType), "text/plain") {
		// hack around the content-type, Context.JSON refuses to work otherwise
		c.Request().Header.Set(echo.HeaderContentType, echo.MIMEApplicationJSONCharsetUTF8)
	}
}

func (a *Authenticator) BeginLoginFlowHandler(c echo.Context) error {
	setJSON(c)

	var flowReq FlowRequest
	err := c.Bind(&flowReq)
	if err != nil {
		return c.String(http.StatusBadRequest, err.Error())
	}

	resp := a.NewFlow(&flowReq)

	if resp == nil {
		return c.String(http.StatusBadRequest, "no such handler")
	}

	return c.JSON(http.StatusOK, resp)
}

func (a *Authenticator) LoginFlowHandler(c echo.Context) error {
	setJSON(c)

	flowID := c.Param("flow_id")

	flow := a.Flows.Get(FlowID(flowID))
	if flow == nil {
		return c.String(http.StatusNotFound, "no such flow")
	}

	return flow.progress(a, c)
}

func (a *Authenticator) InstallRoutes(e *echo.Echo) {
	authG := e.Group("/auth")
	authG.GET("/authorize", a.AuthorizeHandler)
	authG.GET("/providers", a.ProvidersHandler)

	authG.POST("/login_flow", a.BeginLoginFlowHandler)

	loginFlow := authG.Group("/login_flow") // TODO: add IP address affinity middleware
	loginFlow.POST("/:flow_id", a.LoginFlowHandler)
	loginFlow.DELETE("/:flow_id", a.LoginFlowDeleteHandler)

}