package main

import (
	"bytes"
	"crypto/hmac"
	"crypto/sha256"
	"encoding/base64"
	"fmt"
	"log"
	"math/rand"
	"net/mail"
	"regexp"
	"strings"

	"github.com/pyke369/golang-support/rcache"
	"golang.org/x/crypto/openpgp"
)

// AuthProfile interface
type AuthProfile interface {
	Match(string) (bool, error)
	PgpKeys() openpgp.EntityList
}

// AuthProfileRegexp implements auth based on regexp only
type AuthProfileRegexp struct {
	subjectRegexp *regexp.Regexp
	pgpKeys       openpgp.EntityList
}

// AuthProfileLdap implements auth based on regexp then ldap check
type AuthProfileLdap struct {
	subjectRegexp *regexp.Regexp
	ldap          *LdapHandler
}

// JSONRPCACL represents the acls for the json RPC API
type JSONRPCACL struct {
	actions     map[string][]*regexp.Regexp
	pgpProfiles []string
	sslProfiles []string
}

// NewJSONRPCACL instanciates json RPC API ACLs.
func NewJSONRPCACL(regexps map[string][]string, pgpProfiles, sslProfiles []string) *JSONRPCACL {
	realPerms := map[string][]*regexp.Regexp{}
	for action, reg := range regexps {
		realPerms[action] = []*regexp.Regexp{}
		for _, r := range reg {
			realPerms[action] = append(realPerms[action], rcache.Get(fmt.Sprintf("^%s$", r)))
		}
	}
	a := JSONRPCACL{
		actions:     realPerms,
		pgpProfiles: pgpProfiles,
		sslProfiles: sslProfiles,
	}
	return &a
}

// GetListFilters returns the restrictions on the list action (or * if // defined)
func (a JSONRPCACL) GetListFilters(pgpProfiles, sslProfiles []string, method string) []*regexp.Regexp {
	var ret []*regexp.Regexp
	// ignore acl for which the profile doesn't match
	if !inArray(sslProfiles, a.sslProfiles) && !inArray(pgpProfiles, a.pgpProfiles) {
		return nil
	}
	for aclAction, targets := range a.actions {
		if aclAction == "*" || aclAction == method {
			ret = append(ret, targets...)
		}
	}
	return ret
}

// Match method for a json RPC ACL
func (a JSONRPCACL) Match(action, target string, pgpProfiles, sslProfiles []string) bool {
	// ignore acl for which the profile doesn't match
	if !inArray(sslProfiles, a.sslProfiles) && !inArray(pgpProfiles, a.pgpProfiles) {
		return false
	}
	// the profile match somehow, let's test the action
	for aclAction, targets := range a.actions {
		// action must match
		if aclAction != action && aclAction != "*" {
			continue
		}
		// and target must match too
		for _, reg := range targets {
			if reg.MatchString(target) {
				return true
			}
		}
	}
	return false
}

// PdnsACL represents the acls for direct access to the PDNS API
type PdnsACL struct {
	regexp   *regexp.Regexp
	read     bool // Allow GET method
	write    bool // Allow every other method
	profiles []string
}

// NewPdnsACL instanciates ACLs.
func NewPdnsACL(regexp string, perms []string, profiles []string) *PdnsACL {
	a := PdnsACL{
		regexp:   rcache.Get(fmt.Sprintf("^%s$", regexp)),
		profiles: profiles,
		read:     false,
		write:    false,
	}
	for _, v := range perms {
		switch v {
		case "r":
			a.read = true
		case "w":
			a.write = true
		}
	}
	return &a
}

// Match method for an ACL
func (a PdnsACL) Match(path, method string, profiles []string) bool {
	// ignore acl for which the profile doesn't match
	if !inArray(profiles, a.profiles) {
		return false
	}
	// check the method is valid
	if (method == "GET" && !a.read) || (method != "GET" && !a.write) {
		return false
	}
	return a.regexp.MatchString(path)
}

// NewAuthProfileRegexp instanciates a regexp based profile
func NewAuthProfileRegexp(subjectRegexp, pgpKeys string) AuthProfileRegexp {
	p := AuthProfileRegexp{
		subjectRegexp: rcache.Get(fmt.Sprintf("^%s$", subjectRegexp)),
	}
	keyring, err := openpgp.ReadArmoredKeyRing(strings.NewReader(pgpKeys))
	if err == nil {
		p.pgpKeys = keyring
	} else {
		p.pgpKeys = openpgp.EntityList{}
	}
	return p
}

// Match method for Regexp based profile
func (p AuthProfileRegexp) Match(subject string) (bool, error) {
	return p.subjectRegexp.MatchString(subject), nil
}

// PgpKeys Method don't apply for a Regexp based profile
func (p AuthProfileRegexp) PgpKeys() openpgp.EntityList {
	return p.pgpKeys
}

// NewAuthProfileLdap instanciates ldap based profile
func NewAuthProfileLdap(subjectRegexp string, servers []string,
	bindCn, bindPw, baseDN, filter, attr, pgpAttr string, valid []string, ssl bool) (AuthProfileLdap, error) {
	p := AuthProfileLdap{
		subjectRegexp: rcache.Get(fmt.Sprintf("^%s$", subjectRegexp)),
		ldap:          NewLdap(servers, bindCn, bindPw, baseDN, filter, attr, pgpAttr, valid, 10, ssl),
	}
	return p, nil
}

// Match Method for ldap based profile
func (p AuthProfileLdap) Match(subject string) (bool, error) {
	if !p.subjectRegexp.MatchString(subject) {
		return false, nil
	}
	return p.ldap.Auth(subject)
}

// PgpKeys Method for ldap based profile
func (p AuthProfileLdap) PgpKeys() openpgp.EntityList {
	var kr openpgp.EntityList
	ret, err := p.ldap.PgpKeys()
	if err != nil {
		log.Println(err)
		return nil
	}
	if ret == nil {
		return kr
	}
	for _, key := range ret {
		k, err := openpgp.ReadArmoredKeyRing(strings.NewReader(key))
		if err != nil {
			log.Println("Error reading Armored Key: ", err)
			continue
		}
		kr = append(kr, k...)
	}
	return kr
}

// NewSalt generate a nonce
func NewSalt(size int) string {
	var letterRunes = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")
	b := make([]rune, size)
	for i := range b {
		b[i] = letterRunes[rand.Intn(len(letterRunes))]
	}
	return string(b)
}

// ComputeHmac256 return a HMAC, base64 encoded
func ComputeHmac256(message string, secret string) string {
	h := hmac.New(sha256.New, []byte(secret))
	h.Write([]byte(message))
	return strings.TrimRight(base64.StdEncoding.EncodeToString(h.Sum(nil)), "=")
}

// PgpMessageVerify checks a message signature
func PgpMessageVerify(msg []byte, sig []byte, keyring openpgp.EntityList) string {
	// no keyring, no need to try to decode
	if len(keyring) == 0 {
		return ""
	}
	signature := bytes.NewReader(sig)
	message := bytes.NewReader(msg)

	entity, err := openpgp.CheckDetachedSignature(keyring, message, signature)
	if err != nil {
		log.Println(err)
		return ""
	}
	for _, a := range entity.Identities {
		e, err := mail.ParseAddress(a.Name)
		if err != nil {
			log.Println(err)
			return a.Name
		}
		return strings.Split(e.Address, "@")[0]
	}
	return ""
}