//go:build js && wasm

package ultraviolet

import (
	"context"
	"fmt"
	"sync"

	fw "git.buran.team/main/fairwind"
)

type Parameters map[string]any
type NodeBuilder func(uvc *UVContext, parameters Parameters) (*Node, error)

type Route struct {
	Default    bool
	Builder    NodeBuilder
	name       string     // NOTE: sets automatically
	parameters Parameters // NOTE: sets automatically
}

type Routing map[string]*Route

type Router struct {
	ctx     context.Context
	log     *fw.Log
	mutex   sync.Mutex
	uvc     *UVContext
	root    *Node
	routing Routing
	stack   []Route
}

func NewRouter(ctx context.Context, log *fw.Log, uvc *UVContext, routing Routing) (*Router, error) {
	defaultRoute := ""
	for name := range routing {
		if routing[name].Default {
			defaultRoute = name
		}

		routing[name].name = name
	}

	if defaultRoute == "" {
		return nil, ErrNoDefaultRoute
	}

	this := &Router{
		ctx: ctx,
		log: log,
		uvc: uvc,
		root: &Node{
			Component: uvc.Factory().NewRoot(
				RootComponentOptions{},
			),
		},
		routing: routing,
		stack:   []Route{},
	}
	this.Push(defaultRoute, Parameters{}) // NOTE: default router haven't parameters
	return this, nil
}

func (this *Router) Update() {
	this.root.Update()
}

func (this *Router) Push(name string, parameters Parameters) error {
	this.mutex.Lock()
	defer this.mutex.Unlock()

	route, ok := this.routing[name]
	if !ok {
		return ErrRouteNotFound
	}

	this.stack = append(
		this.stack,
		Route{
			name:       name,
			parameters: parameters,
			Builder:    route.Builder,
		},
	)

	go func() {
		err := this.refresh()
		if err != nil {
			this.log.Error("can't refresh", fw.LogError(err))
		}
	}()

	return nil
}

func (this *Router) Pop() (Route, error) {
	this.mutex.Lock()
	defer this.mutex.Unlock()

	if len(this.stack) == 0 {
		return Route{}, ErrStackUnderflow
	}

	result := this.stack[len(this.stack)-1]
	this.stack = this.stack[:len(this.stack)-1]

	go func() {
		err := this.refresh()
		if err != nil {
			this.log.Error("can't refresh", fw.LogError(err))
		}
	}()

	return result, nil
}

func (this *Router) Back() {
	_, err := this.Pop()
	if err != nil {
		this.log.Error("can't back on router stack", fw.LogError(err))
	}
}

func (this *Router) Set(name string, parameters Parameters) error {
	this.mutex.Lock()
	defer this.mutex.Unlock()

	route, ok := this.routing[name]
	if !ok {
		return ErrRouteNotFound
	}

	this.stack = []Route{
		{
			name:       name,
			parameters: parameters,
			Builder:    route.Builder,
		},
	}

	go func() {
		err := this.refresh()
		if err != nil {
			this.log.Error("can't refresh", fw.LogError(err))
		}
	}()

	return nil
}

func (this *Router) refresh() error {
	if len(this.stack) == 0 {
		return ErrStackUnderflow
	}

	// Get route
	route := this.stack[len(this.stack)-1]

	// Build new window
	child, err := route.Builder(
		this.uvc,
		route.parameters,
	)
	if err != nil {
		return fmt.Errorf("can't refresh router: %w", err)
	}

	// Set new window
	this.root.Build(child)
	return nil
}