package main

import (
	"crypto/sha256"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net/http"
	"strings"
)

type Group struct {
	GroupId      int64
	Name         string
	Password     string `db:"-"`
	PasswordHash string `json:"-"`
}

type GroupList struct {
	Groups *[]*Group `json:"groups"`
}

type GroupExistsError struct{}

func (gee GroupExistsError) Error() string {
	return "Group exists"
}

func (g *Group) Write(w http.ResponseWriter) error {
	enc := json.NewEncoder(w)
	return enc.Encode(g)
}

func (g *Group) Read(json_str string) error {
	dec := json.NewDecoder(strings.NewReader(json_str))
	return dec.Decode(g)
}

func (gl *GroupList) Write(w http.ResponseWriter) error {
	enc := json.NewEncoder(w)
	return enc.Encode(gl)
}

func (g *Group) HashPassword() {
	password_hasher := sha256.New()
	io.WriteString(password_hasher, g.Password)
	g.PasswordHash = fmt.Sprintf("%x", password_hasher.Sum(nil))
	g.Password = ""
}

func GetGroup(groupid int64) (*Group, error) {
	var g Group

	err := DB.SelectOne(&g, "SELECT * from groups where GroupId=?", groupid)
	if err != nil {
		return nil, err
	}
	return &g, nil
}

func ValidGroup(groupid int64, password string) (bool, error) {
	var test Group
	test.Password = password
	test.HashPassword()

	group, err := GetGroup(groupid)
	if err != nil {
		return false, err
	} else {
		return group.PasswordHash == test.PasswordHash, nil
	}
}

func GetGroups() (*[]*Group, error) {
	var groups []*Group

	_, err := DB.Select(&groups, "SELECT * from groups")
	if err != nil {
		return nil, err
	}
	return &groups, nil
}

func GetGroupByName(groupname string) (*Group, error) {
	var g Group

	err := DB.SelectOne(&g, "SELECT * from groups where Name=?", groupname)
	if err != nil {
		return nil, err
	}
	return &g, nil
}

func InsertGroup(g *Group) error {
	transaction, err := DB.Begin()
	if err != nil {
		return err
	}

	existing, err := transaction.SelectInt("SELECT count(*) from groups where Name=?", g.Name)
	if err != nil {
		transaction.Rollback()
		return err
	}
	if existing > 0 {
		transaction.Rollback()
		return GroupExistsError{}
	}

	err = transaction.Insert(g)
	if err != nil {
		transaction.Rollback()
		return err
	}

	err = transaction.Commit()
	if err != nil {
		transaction.Rollback()
		return err
	}

	return nil
}

func GroupHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method == "POST" {
		group_json := r.PostFormValue("group")
		if group_json == "" {
			WriteError(w, 3 /*Invalid Request*/)
			return
		}

		var group Group
		err := group.Read(group_json)
		if err != nil {
			WriteError(w, 3 /*Invalid Request*/)
			return
		}
		group.GroupId = -1
		group.HashPassword()

		err = InsertGroup(&group)
		if err != nil {
			if _, ok := err.(GroupExistsError); ok {
				WriteError(w, 9 /*Group Exists*/)
			} else {
				WriteError(w, 999 /*Internal Error*/)
				log.Print(err)
			}
			return
		}

		w.WriteHeader(201 /*Created*/)
		err = group.Write(w)
		if err != nil {
			WriteError(w, 999 /*Internal Error*/)
			log.Print(err)
			return
		}
	} else if r.Method == "GET" {
		var gl GroupList

		groups, err := GetGroups()
		if err != nil {
			WriteError(w, 999 /*Internal Error*/)
			log.Print(err)
			return
		}

		gl.Groups = groups
		err = (&gl).Write(w)
		if err != nil {
			WriteError(w, 999 /*Internal Error*/)
			log.Print(err)
			return
		}
	} else if r.Method == "PUT" {
		user, err := GetUserFromSession(r)
		if err != nil {
			WriteError(w, 1 /*Not Signed In*/)
			return
		}

		groupid, err := GetURLID(r.URL.Path)
		if err != nil {
			WriteError(w, 3 /*Invalid Request*/)
			return
		}

		if groupid != user.GroupId {
			WriteError(w, 2 /*Unauthorized Access*/)
			return
		}

		group_json := r.PostFormValue("group")
		if group_json == "" {
			WriteError(w, 3 /*Invalid Request*/)
			return
		}

		group, err := GetGroup(groupid)
		if err != nil {
			WriteError(w, 999 /*Internal Error*/)
			log.Print(err)
			return
		}

		// Save old PWHash in case the new password is bogus
		old_pwhash := group.PasswordHash

		err = group.Read(group_json)
		if err != nil || group.GroupId != groupid {
			WriteError(w, 3 /*Invalid Request*/)
			return
		}

		// If the user didn't create a new password for the group, keep the old one
		if group.Password != BogusPassword {
			group.HashPassword()
		} else {
			group.Password = ""
			group.PasswordHash = old_pwhash
		}

		count, err := DB.Update(group)
		if count != 1 || err != nil {
			WriteError(w, 999 /*Internal Error*/)
			log.Print(err)
			return
		}

		err = group.Write(w)
		if err != nil {
			WriteError(w, 999 /*Internal Error*/)
			log.Print(err)
			return
		}
	} else { /* DELETE not implemented*/
		WriteError(w, 3 /*Invalid Request*/)
		return
	}
}