package router

import (
	"fmt"
	"strings"
)

/* routeElement contains a pre-compiled route pattern */
type routeElement struct {
	originalPath string
	parsedPath   string
	parsedArgs   int
}

/* Router object is safe for concurrent use after construction */
type Router struct {
	urlMap map[string]routeElement
}

/* addRoute adds or sets routing element in urlMap */
func (r *Router) addRoute(key string, path string) error {
	if _, ok := r.urlMap[key]; ok {
		return ErrKeyExists
	}
	/* pre-compile path and replace path values with %v */
	pathBuffer := strings.Builder{}
	pathBuffer.Grow(len(path))
	placeholderCount := 0
	for idx := 0; idx < len(path); {
		/* look for open bracket */
		if path[idx] == '{' {
			/* look for corresponding closing bracket */
			closing := strings.IndexByte(path[idx:], '}')
			if closing == -1 {
				/* broken pattern, fail */
				return ErrBrokenPattern
			}
			pathBuffer.WriteString("%v")
			placeholderCount++
			idx += closing + 1
			continue
		}
		pathBuffer.WriteByte(path[idx])
		idx++
	}
	/* save pre-compiled path */
	r.urlMap[key] = routeElement{
		originalPath: path,
		parsedPath:   pathBuffer.String(),
		parsedArgs:   placeholderCount,
	}
	return nil

}

/* Route returns path  route by key */
func (r *Router) Route(key string, args ...any) (string, error) {
	/* lookup path in the database */
	element, ok := r.urlMap[key]
	if !ok {
		return "", ErrMissingKey
	}
	/* return path unchanged if there are no arguments */
	if len(args) != element.parsedArgs {
		return "", ErrArgMismatch
	}
	return fmt.Sprintf(element.parsedPath, args...), nil
}

/* Pattern returns original path */
func (r *Router) Pattern(key string) (string, error) {
	if element, ok := r.urlMap[key]; ok {
		return element.originalPath, nil
	}
	return "", ErrMissingKey
}