// 2020 Rackspace, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License"): you may
// not use this file except in compliance with the License. You may obtain
// a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations
// under the License.

package netparse

import (
	"regexp"
	"strconv"
	"strings"
)

var (
	ipAclRE    = regexp.MustCompile(`(?i)(i|)(p|pv6)\s+access-list\s+(\S+)\n((.|\n)*?)(\n\S|$)`)
	ipExtAclRE = regexp.MustCompile(`(?i)(i|)(p|pv6)\s+access-list\s+extended\s+(\S+)\n((.|\n)*?)(\n\S|$)`)
	lineAclRE  = regexp.MustCompile(`(?i)([0-9]+)\s+(.*?)$`)
)

type (
	// ACL struct describes the parsed items within a access-list
	ACL struct {
		Name     string    `json:"name"`
		IPV6     bool      `json:"ipv6"`
		Extended bool      `json:"extended"`
		Rules    []ACLRule `json:"rules"`
	}

	// ACLRule struct describes the parsed items within a single
	// access-list entry
	ACLRule struct {
		Line int    `json:"line"`
		Rule string `json:"rule"`
	}
)

// ACLParse is the parsing method for the ACL struct. This
func ACLParse(s string) []ACL {
	retVal := make([]ACL, 0)
	for _, acl := range ipAclRE.FindAllStringSubmatch(s, -1) {
		retVal = append(retVal, ACL{
			Name:  acl[3],
			IPV6:  isV6(acl[2]),
			Rules: parseACL(acl[4]),
		})
	}

	for _, acl := range ipExtAclRE.FindAllStringSubmatch(s, -1) {
		retVal = append(retVal, ACL{
			Name:     acl[3],
			IPV6:     isV6(acl[2]),
			Extended: true,
			Rules:    parseACL(acl[4]),
		})
	}
	return retVal
}

func isV6(s string) bool {
	return s == "pv6"
}

func parseACL(s string) []ACLRule {
	retVal := make([]ACLRule, 0)
	for i, r := range strings.Split(s, "\n") {
		r = strings.TrimSpace(r)
		if r == "" {
			continue
		}
		m := lineAclRE.FindStringSubmatch(r)
		if len(m) == 0 {
			retVal = append(retVal, ACLRule{Line: i + 1, Rule: r})
			continue
		}
		retVal = append(retVal, ACLRule{
			Line: func() int {
				if n, err := strconv.Atoi(m[1]); err == nil {
					return n
				}
				return 0
			}(),
			Rule: m[2],
		})
	}
	return retVal
}