package main

import (
	"encoding/json"
	"errors"
	"log"
	"net/http"
	"strings"
	"time"
)

type Attendee struct {
	AttendeeId int64
	UserId     int64 `json:"-"`
	Name       string
	Date       time.Time `json:"-"`
}

type PopularAttendee struct {
	Name       string
	Popularity int64
}

type AttendeeList struct {
	Attendees *[]*Attendee `json:"attendees"`
}

type PopularAttendeeList struct {
	PopularAttendees *[]*PopularAttendee `json:"popularattendees"`
}

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

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

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

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

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

type AttendeeExistsError struct{}

func (aeu AttendeeExistsError) Error() string {
	return "Attendee exists"
}

func GetAttendees(userid int64, date time.Time) (*[]*Attendee, error) {
	var attendees []*Attendee

	_, err := DB.Select(&attendees, "SELECT * from attendees WHERE UserId=? AND Date=?", userid, date)
	if err != nil {
		return nil, err
	}
	return &attendees, nil
}

func GetPopularAttendees() (*[]*PopularAttendee, error) {
	var attendees []*Attendee
	attendeeMap := make(map[string]int64)
	popularAttendees := make([]*PopularAttendee, 0)

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

	for i := range attendees {
		attendeeMap[attendees[i].Name] += 1
	}
	for name, count := range attendeeMap {
		var popularAttendee PopularAttendee
		popularAttendee.Name = name
		popularAttendee.Popularity = count
		popularAttendees = append(popularAttendees, &popularAttendee)
	}

	return &popularAttendees, nil
}

func InsertAttendee(a *Attendee) error {
	transaction, err := DB.Begin()
	if err != nil {
		return err
	}

	existing, err := transaction.SelectInt("SELECT count(*) from attendees where UserId=? AND Name=? AND Date=?", a.UserId, a.Name, a.Date)
	if err != nil {
		transaction.Rollback()
		return err
	}
	if existing > 0 {
		transaction.Rollback()
		return AttendeeExistsError{}
	}

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

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

	return nil
}

func GetAttendee(attendeeid int64, userid int64, date time.Time) (*Attendee, error) {
	var a Attendee

	err := DB.SelectOne(&a, "SELECT * from attendees where UserId=? AND AttendeeId=? AND Date=?", userid, attendeeid, date)
	if err != nil {
		return nil, err
	}
	return &a, nil
}

func DeleteAttendee(a *Attendee) error {
	transaction, err := DB.Begin()
	if err != nil {
		return err
	}

	// TODO ensure attendee isn't used in any suggestions

	count, err := transaction.Delete(a)
	if err != nil {
		transaction.Rollback()
		return err
	}
	if count != 1 {
		transaction.Rollback()
		return errors.New("Was going to delete more than one attendee")
	}

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

	return nil
}

func AttendeeHandler(w http.ResponseWriter, r *http.Request) {
	user, err := GetUserFromSession(r)
	if err != nil {
		WriteError(w, 1 /*Not Signed In*/)
		return
	}

	today := time.Now().UTC().Truncate(time.Hour * 24)

	if r.Method == "POST" {
		attendee_json := r.PostFormValue("attendee")
		if attendee_json == "" {
			WriteError(w, 3 /*Invalid Request*/)
			return
		}

		var attendee Attendee
		err := attendee.Read(attendee_json)
		if err != nil {
			WriteError(w, 3 /*Invalid Request*/)
			return
		}
		attendee.AttendeeId = -1
		attendee.UserId = user.UserId
		attendee.Date = today

		err = InsertAttendee(&attendee)
		if err != nil {
			if _, ok := err.(AttendeeExistsError); ok {
				WriteError(w, 5 /*Attendee Exists*/)
			} else {
				WriteError(w, 999 /*Internal Error*/)
				log.Print(err)
			}
			return
		}

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

		attendees, err := GetAttendees(user.UserId, today)
		if err != nil {
			WriteError(w, 999 /*Internal Error*/)
			log.Print(err)
			return
		}

		al.Attendees = attendees
		err = (&al).Write(w)
		if err != nil {
			WriteError(w, 999 /*Internal Error*/)
			log.Print(err)
			return
		}
	} else if r.Method == "DELETE" {
		attendeeid, err := GetURLID(r.URL.Path)
		if err != nil {
			WriteError(w, 3 /* Invalid Request */)
			return
		}

		attendee, err := GetAttendee(attendeeid, user.UserId, today)
		if err != nil {
			WriteError(w, 3 /*Invalid Request*/)
			return
		}

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

		WriteSuccess(w)
	} else {
		/* No PUT */
		WriteError(w, 3 /*Invalid Request*/)
		return
	}
}

func PopularAttendeeHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method == "GET" {
		var pal PopularAttendeeList

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

		pal.PopularAttendees = attendees
		err = (&pal).Write(w)
		if err != nil {
			WriteError(w, 999 /*Internal Error*/)
			log.Print(err)
			return
		}
	} else {
		/* No POST, PUT, or DELETE */
		WriteError(w, 3 /*Invalid Request*/)
		return
	}
}