// ⚡️ Fiber is an Express inspired web framework written in Go with ☕️
// 🤖 Github Repository: https://github.com/gofiber/fiber
// 📌 API Documentation: https://docs.gofiber.io

package fiber

import (
	"errors"
	"fmt"
	"html"
	"sort"
	"strings"
	"sync/atomic"

	"github.com/gofiber/utils/v2"
	"github.com/valyala/fasthttp"
)

// Router defines all router handle interface, including app and group router.
type Router interface {
	Use(args ...any) Router

	Get(path string, handler Handler, middleware ...Handler) Router
	Head(path string, handler Handler, middleware ...Handler) Router
	Post(path string, handler Handler, middleware ...Handler) Router
	Put(path string, handler Handler, middleware ...Handler) Router
	Delete(path string, handler Handler, middleware ...Handler) Router
	Connect(path string, handler Handler, middleware ...Handler) Router
	Options(path string, handler Handler, middleware ...Handler) Router
	Trace(path string, handler Handler, middleware ...Handler) Router
	Patch(path string, handler Handler, middleware ...Handler) Router

	Add(methods []string, path string, handler Handler, middleware ...Handler) Router
	All(path string, handler Handler, middleware ...Handler) Router

	Group(prefix string, handlers ...Handler) Router

	Route(path string) Register

	Name(name string) Router
}

// Route is a struct that holds all metadata for each registered handler.
type Route struct {
	// ### important: always keep in sync with the copy method "app.copyRoute" ###
	// Data for routing
	pos         uint32      // Position in stack -> important for the sort of the matched routes
	use         bool        // USE matches path prefixes
	mount       bool        // Indicated a mounted app on a specific route
	star        bool        // Path equals '*'
	root        bool        // Path equals '/'
	path        string      // Prettified path
	routeParser routeParser // Parameter parser
	group       *Group      // Group instance. used for routes in groups

	// Public fields
	Method string `json:"method"` // HTTP method
	Name   string `json:"name"`   // Route's name
	//nolint:revive // Having both a Path (uppercase) and a path (lowercase) is fine
	Path     string    `json:"path"`   // Original registered route path
	Params   []string  `json:"params"` // Case sensitive param keys
	Handlers []Handler `json:"-"`      // Ctx handlers
}

func (r *Route) match(detectionPath, path string, params *[maxParams]string) bool {
	// root detectionPath check
	if r.root && detectionPath == "/" {
		return true
		// '*' wildcard matches any detectionPath
	} else if r.star {
		if len(path) > 1 {
			params[0] = path[1:]
		} else {
			params[0] = ""
		}
		return true
	}
	// Does this route have parameters
	if len(r.Params) > 0 {
		// Match params
		if match := r.routeParser.getMatch(detectionPath, path, params, r.use); match {
			// Get params from the path detectionPath
			return match
		}
	}
	// Is this route a Middleware?
	if r.use {
		// Single slash will match or detectionPath prefix
		if r.root || strings.HasPrefix(detectionPath, r.path) {
			return true
		}
		// Check for a simple detectionPath match
	} else if len(r.path) == len(detectionPath) && r.path == detectionPath {
		return true
	}
	// No match
	return false
}

func (app *App) nextCustom(c CustomCtx) (bool, error) { //nolint: unparam // bool param might be useful for testing
	// Get stack length
	tree, ok := app.treeStack[c.getMethodINT()][c.getTreePath()]
	if !ok {
		tree = app.treeStack[c.getMethodINT()][""]
	}
	lenr := len(tree) - 1

	// Loop over the route stack starting from previous index
	for c.getIndexRoute() < lenr {
		// Increment route index
		c.setIndexRoute(c.getIndexRoute() + 1)

		// Get *Route
		route := tree[c.getIndexRoute()]

		// Check if it matches the request path
		match := route.match(c.getDetectionPath(), c.Path(), c.getValues())

		// No match, next route
		if !match {
			continue
		}
		// Pass route reference and param values
		c.setRoute(route)

		// Non use handler matched
		if !c.getMatched() && !route.use {
			c.setMatched(true)
		}

		// Execute first handler of route
		c.setIndexHandler(0)
		err := route.Handlers[0](c)
		return match, err // Stop scanning the stack
	}

	// If c.Next() does not match, return 404
	err := NewError(StatusNotFound, "Cannot "+c.Method()+" "+c.getPathOriginal())

	// If no match, scan stack again if other methods match the request
	// Moved from app.handler because middleware may break the route chain
	if !c.getMatched() && app.methodExistCustom(c) {
		err = ErrMethodNotAllowed
	}
	return false, err
}

func (app *App) next(c *DefaultCtx) (bool, error) {
	// Get stack length
	tree, ok := app.treeStack[c.methodINT][c.treePath]
	if !ok {
		tree = app.treeStack[c.methodINT][""]
	}
	lenTree := len(tree) - 1

	// Loop over the route stack starting from previous index
	for c.indexRoute < lenTree {
		// Increment route index
		c.indexRoute++

		// Get *Route
		route := tree[c.indexRoute]

		var match bool
		var err error
		// skip for mounted apps
		if route.mount {
			continue
		}

		// Check if it matches the request path
		match = route.match(c.detectionPath, c.path, &c.values)
		if !match {
			// No match, next route
			continue
		}
		// Pass route reference and param values
		c.route = route

		// Non use handler matched
		if !c.matched && !route.use {
			c.matched = true
		}

		// Execute first handler of route
		c.indexHandler = 0
		if len(route.Handlers) > 0 {
			err = route.Handlers[0](c)
		}
		return match, err // Stop scanning the stack
	}

	// If c.Next() does not match, return 404
	err := NewError(StatusNotFound, "Cannot "+c.method+" "+html.EscapeString(c.pathOriginal))
	if !c.matched && app.methodExist(c) {
		// If no match, scan stack again if other methods match the request
		// Moved from app.handler because middleware may break the route chain
		err = ErrMethodNotAllowed
	}
	return false, err
}

func (app *App) requestHandler(rctx *fasthttp.RequestCtx) {
	// Handler for default ctxs
	var c CustomCtx
	var ok bool
	if app.newCtxFunc != nil {
		c, ok = app.AcquireCtx(rctx).(CustomCtx)
		if !ok {
			panic(errors.New("requestHandler: failed to type-assert to CustomCtx"))
		}
	} else {
		c, ok = app.AcquireCtx(rctx).(*DefaultCtx)
		if !ok {
			panic(errors.New("requestHandler: failed to type-assert to *DefaultCtx"))
		}
	}
	defer app.ReleaseCtx(c)

	// handle invalid http method directly
	if app.methodInt(c.Method()) == -1 {
		_ = c.SendStatus(StatusNotImplemented) //nolint:errcheck // Always return nil
		return
	}

	// check flash messages
	if strings.Contains(utils.UnsafeString(c.Request().Header.RawHeaders()), FlashCookieName) {
		c.Redirect().parseAndClearFlashMessages()
	}

	// Find match in stack
	var err error
	if app.newCtxFunc != nil {
		_, err = app.nextCustom(c)
	} else {
		_, err = app.next(c.(*DefaultCtx))
	}
	if err != nil {
		if catch := c.App().ErrorHandler(c, err); catch != nil {
			_ = c.SendStatus(StatusInternalServerError) //nolint:errcheck // It is fine to ignore the error here
		}
		// TODO: Do we need to return here?
	}
}

func (app *App) addPrefixToRoute(prefix string, route *Route) *Route {
	prefixedPath := getGroupPath(prefix, route.Path)
	prettyPath := prefixedPath
	// Case-sensitive routing, all to lowercase
	if !app.config.CaseSensitive {
		prettyPath = utils.ToLower(prettyPath)
	}
	// Strict routing, remove trailing slashes
	if !app.config.StrictRouting && len(prettyPath) > 1 {
		prettyPath = strings.TrimRight(prettyPath, "/")
	}

	route.Path = prefixedPath
	route.path = RemoveEscapeChar(prettyPath)
	route.routeParser = parseRoute(prettyPath, app.customConstraints...)
	route.root = false
	route.star = false

	return route
}

func (*App) copyRoute(route *Route) *Route {
	return &Route{
		// Router booleans
		use:   route.use,
		mount: route.mount,
		star:  route.star,
		root:  route.root,

		// Path data
		path:        route.path,
		routeParser: route.routeParser,

		// misc
		pos: route.pos,

		// Public data
		Path:     route.Path,
		Params:   route.Params,
		Name:     route.Name,
		Method:   route.Method,
		Handlers: route.Handlers,
	}
}

func (app *App) register(methods []string, pathRaw string, group *Group, handler Handler, middleware ...Handler) {
	handlers := middleware
	if handler != nil {
		handlers = append(handlers, handler)
	}

	for _, method := range methods {
		// Uppercase HTTP methods
		method = utils.ToUpper(method)
		// Check if the HTTP method is valid unless it's USE
		if method != methodUse && app.methodInt(method) == -1 {
			panic(fmt.Sprintf("add: invalid http method %s\n", method))
		}
		// is mounted app
		isMount := group != nil && group.app != app
		// A route requires atleast one ctx handler
		if len(handlers) == 0 && !isMount {
			panic(fmt.Sprintf("missing handler/middleware in route: %s\n", pathRaw))
		}
		// Cannot have an empty path
		if pathRaw == "" {
			pathRaw = "/"
		}
		// Path always start with a '/'
		if pathRaw[0] != '/' {
			pathRaw = "/" + pathRaw
		}
		// Create a stripped path in-case sensitive / trailing slashes
		pathPretty := pathRaw
		// Case-sensitive routing, all to lowercase
		if !app.config.CaseSensitive {
			pathPretty = utils.ToLower(pathPretty)
		}
		// Strict routing, remove trailing slashes
		if !app.config.StrictRouting && len(pathPretty) > 1 {
			pathPretty = strings.TrimRight(pathPretty, "/")
		}
		// Is layer a middleware?
		isUse := method == methodUse
		// Is path a direct wildcard?
		isStar := pathPretty == "/*"
		// Is path a root slash?
		isRoot := pathPretty == "/"
		// Parse path parameters
		parsedRaw := parseRoute(pathRaw, app.customConstraints...)
		parsedPretty := parseRoute(pathPretty, app.customConstraints...)

		// Create route metadata without pointer
		route := Route{
			// Router booleans
			use:   isUse,
			mount: isMount,
			star:  isStar,
			root:  isRoot,

			// Path data
			path:        RemoveEscapeChar(pathPretty),
			routeParser: parsedPretty,
			Params:      parsedRaw.params,

			// Group data
			group: group,

			// Public data
			Path:     pathRaw,
			Method:   method,
			Handlers: handlers,
		}
		// Increment global handler count
		atomic.AddUint32(&app.handlersCount, uint32(len(handlers)))

		// Middleware route matches all HTTP methods
		if isUse {
			// Add route to all HTTP methods stack
			for _, m := range app.config.RequestMethods {
				// Create a route copy to avoid duplicates during compression
				r := route
				app.addRoute(m, &r, isMount)
			}
		} else {
			// Add route to stack
			app.addRoute(method, &route, isMount)
		}
	}
}

func (app *App) addRoute(method string, route *Route, isMounted ...bool) {
	// Check mounted routes
	var mounted bool
	if len(isMounted) > 0 {
		mounted = isMounted[0]
	}

	// Get unique HTTP method identifier
	m := app.methodInt(method)

	// prevent identically route registration
	l := len(app.stack[m])
	if l > 0 && app.stack[m][l-1].Path == route.Path && route.use == app.stack[m][l-1].use && !route.mount && !app.stack[m][l-1].mount {
		preRoute := app.stack[m][l-1]
		preRoute.Handlers = append(preRoute.Handlers, route.Handlers...)
	} else {
		// Increment global route position
		route.pos = atomic.AddUint32(&app.routesCount, 1)
		route.Method = method
		// Add route to the stack
		app.stack[m] = append(app.stack[m], route)
		app.routesRefreshed = true
	}

	// Execute onRoute hooks & change latestRoute if not adding mounted route
	if !mounted {
		app.mutex.Lock()
		app.latestRoute = route
		if err := app.hooks.executeOnRouteHooks(*route); err != nil {
			panic(err)
		}
		app.mutex.Unlock()
	}
}

// buildTree build the prefix tree from the previously registered routes
func (app *App) buildTree() *App {
	if !app.routesRefreshed {
		return app
	}

	// loop all the methods and stacks and create the prefix tree
	for m := range app.config.RequestMethods {
		tsMap := make(map[string][]*Route)
		for _, route := range app.stack[m] {
			treePath := ""
			if len(route.routeParser.segs) > 0 && len(route.routeParser.segs[0].Const) >= 3 {
				treePath = route.routeParser.segs[0].Const[:3]
			}
			// create tree stack
			tsMap[treePath] = append(tsMap[treePath], route)
		}
		app.treeStack[m] = tsMap
	}

	// loop the methods and tree stacks and add global stack and sort everything
	for m := range app.config.RequestMethods {
		tsMap := app.treeStack[m]
		for treePart := range tsMap {
			if treePart != "" {
				// merge global tree routes in current tree stack
				tsMap[treePart] = uniqueRouteStack(append(tsMap[treePart], tsMap[""]...))
			}
			// sort tree slices with the positions
			slc := tsMap[treePart]
			sort.Slice(slc, func(i, j int) bool { return slc[i].pos < slc[j].pos })
		}
	}
	app.routesRefreshed = false

	return app
}