package router

import (
	"fmt"
)

// Handler function that takes parameters as strings
type Handler func(params []string)

type node struct {
	segment    string
	handlerID  int
	children   []*node
	isDynamic  bool
	isWildcard bool
	maxParams  uint8
}

type Router struct {
	get, post, put, patch, delete *node
	paramsBuffer                  []string
}

// Params holds URL parameters
type Params struct {
	Keys   []string
	Values []string
}

// Get returns a parameter value by name
func (p *Params) Get(name string) string {
	for i, key := range p.Keys {
		if key == name && i < len(p.Values) {
			return p.Values[i]
		}
	}
	return ""
}

// New creates a new Router instance
func New() *Router {
	return &Router{
		get:          &node{},
		post:         &node{},
		put:          &node{},
		patch:        &node{},
		delete:       &node{},
		paramsBuffer: make([]string, 64),
	}
}

func (r *Router) methodNode(method string) *node {
	switch method {
	case "GET":
		return r.get
	case "POST":
		return r.post
	case "PUT":
		return r.put
	case "PATCH":
		return r.patch
	case "DELETE":
		return r.delete
	default:
		return nil
	}
}

// AddRoute adds a route with handler ID (for compatibility)
func (r *Router) AddRoute(method, path string, handlerID int) error {
	root := r.methodNode(method)
	if root == nil {
		return fmt.Errorf("unsupported method: %s", method)
	}

	// Create a handler that stores the ID
	h := func(params []string) {
		// This is a placeholder - the actual execution happens in HTTP module
	}

	return r.addRoute(root, path, h, handlerID)
}

// readSegment extracts the next path segment
func readSegment(path string, start int) (segment string, end int, hasMore bool) {
	if start >= len(path) {
		return "", start, false
	}
	if path[start] == '/' {
		start++
	}
	if start >= len(path) {
		return "", start, false
	}
	end = start
	for end < len(path) && path[end] != '/' {
		end++
	}
	return path[start:end], end, end < len(path)
}

// addRoute adds a new route to the trie
func (r *Router) addRoute(root *node, path string, h Handler, handlerID int) error {
	if path == "/" {
		root.handlerID = handlerID
		return nil
	}

	current := root
	pos := 0
	lastWC := false
	count := uint8(0)

	for {
		seg, newPos, more := readSegment(path, pos)
		if seg == "" {
			break
		}

		isDyn := len(seg) > 1 && seg[0] == ':'
		isWC := len(seg) > 0 && seg[0] == '*'

		if isWC {
			if lastWC || more {
				return fmt.Errorf("wildcard must be the last segment in the path")
			}
			lastWC = true
		}

		if isDyn || isWC {
			count++
		}

		var child *node
		for _, c := range current.children {
			if c.segment == seg {
				child = c
				break
			}
		}

		if child == nil {
			child = &node{segment: seg, isDynamic: isDyn, isWildcard: isWC}
			current.children = append(current.children, child)
		}

		if child.maxParams < count {
			child.maxParams = count
		}

		current = child
		pos = newPos
	}

	current.handlerID = handlerID
	return nil
}

// Lookup finds a handler matching method and path
func (r *Router) Lookup(method, path string) (int, *Params, bool) {
	root := r.methodNode(method)
	if root == nil {
		return 0, nil, false
	}

	if path == "/" {
		if root.handlerID != 0 {
			return root.handlerID, &Params{}, true
		}
		return 0, nil, false
	}

	buffer := r.paramsBuffer
	if cap(buffer) < int(root.maxParams) {
		buffer = make([]string, root.maxParams)
		r.paramsBuffer = buffer
	}
	buffer = buffer[:0]

	handlerID, paramCount, paramKeys, found := r.match(root, path, 0, &buffer)
	if !found {
		return 0, nil, false
	}

	params := &Params{
		Keys:   paramKeys,
		Values: buffer[:paramCount],
	}

	return handlerID, params, true
}

// match traverses the trie to find a handler
func (r *Router) match(current *node, path string, start int, params *[]string) (int, int, []string, bool) {
	paramCount := 0
	var paramKeys []string

	// Check wildcards first
	for _, c := range current.children {
		if c.isWildcard {
			rem := path[start:]
			if len(rem) > 0 && rem[0] == '/' {
				rem = rem[1:]
			}
			*params = append(*params, rem)
			// Extract param name from *name format
			paramName := c.segment[1:] // Remove the * prefix
			paramKeys = append(paramKeys, paramName)
			return c.handlerID, 1, paramKeys, c.handlerID != 0
		}
	}

	seg, pos, more := readSegment(path, start)
	if seg == "" {
		return current.handlerID, 0, paramKeys, current.handlerID != 0
	}

	for _, c := range current.children {
		if c.segment == seg || c.isDynamic {
			if c.isDynamic {
				*params = append(*params, seg)
				// Extract param name from :name format
				paramName := c.segment[1:] // Remove the : prefix
				paramKeys = append(paramKeys, paramName)
				paramCount++
			}

			if !more {
				return c.handlerID, paramCount, paramKeys, c.handlerID != 0
			}

			handlerID, nestedCount, nestedKeys, ok := r.match(c, path, pos, params)
			if ok {
				allKeys := append(paramKeys, nestedKeys...)
				return handlerID, paramCount + nestedCount, allKeys, true
			}
		}
	}

	return 0, 0, nil, false
}