package main

import (
	"encoding/json"
	"errors"
	"gopkg.in/gorp.v1"
	"log"
	"net/http"
	"strings"
	"time"
)

type Suggestion struct {
	SuggestionId   int64
	VetoingId      int64 // -1 for initial suggestion
	AttendeeId     int64
	UserId         int64 `json:"-"`
	RestaurantName string
	Date           time.Time `json:"-"`
}

type PopularSuggestion struct {
	RestaurantName string
	Popularity     int64
}

type SuggestionList struct {
	Suggestions *[]*Suggestion `json:"suggestions"`
}

type PopularSuggestionList struct {
	PopularSuggestions *[]*PopularSuggestion `json:"popularsuggestions"`
}

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

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

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

type SuggestionExistsError struct{}

func (aeu SuggestionExistsError) Error() string {
	return "Suggestion exists"
}

type SuggestionNotLastError struct{}

func (snle SuggestionNotLastError) Error() string {
	return "Suggestion not last on the stack"
}
func (s *PopularSuggestion) Write(w http.ResponseWriter) error {
	enc := json.NewEncoder(w)
	return enc.Encode(s)
}

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

func GetAttendeesSuggestions(transaction *gorp.Transaction, userid int64, date time.Time, attendeeid int64) (*[]*Suggestion, error) {
	var suggestions []*Suggestion

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

func GetSuggestions(userid int64, date time.Time) (*[]*Suggestion, error) {
	var suggestions []*Suggestion

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

func GetSuggestion(suggestionid int64, userid int64, date time.Time) (*Suggestion, error) {
	var s Suggestion

	err := DB.SelectOne(&s, "SELECT * from suggestions where UserId=? AND SuggestionId=? AND Date=?", userid, suggestionid, date)
	if err != nil {
		return nil, err
	}
	return &s, nil
}

func VetoedBy(transaction *gorp.Transaction, suggestion *Suggestion) (*[]*Suggestion, error) {
	var suggestions []*Suggestion

	_, err := transaction.Select(&suggestions, "SELECT * from suggestions WHERE UserId=? AND Date=? AND VetoingId=?", suggestion.UserId, suggestion.Date, suggestion.SuggestionId)
	if err != nil {
		return nil, err
	}
	return &suggestions, nil
}

func GetPopularSuggestions() (*[]*PopularSuggestion, error) {
	var suggestions []*Suggestion
	suggestionMap := make(map[string]int64)
	popularSuggestions := make([]*PopularSuggestion, 0)

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

	for i := range suggestions {
		suggestionMap[suggestions[i].RestaurantName] += 1
	}
	for name, count := range suggestionMap {
		var popularSuggestion PopularSuggestion
		popularSuggestion.RestaurantName = name
		popularSuggestion.Popularity = count
		popularSuggestions = append(popularSuggestions, &popularSuggestion)
	}
	return &popularSuggestions, nil
}

func InsertSuggestion(s *Suggestion) error {
	transaction, err := DB.Begin()
	if err != nil {
		return err
	}

	existing, err := transaction.SelectInt("SELECT count(*) from suggestions where RestaurantName=? AND UserId=? AND Date=?", s.RestaurantName, s.UserId, s.Date)
	if err != nil {
		transaction.Rollback()
		return err
	}
	if existing > 0 {
		transaction.Rollback()
		return SuggestionExistsError{}
	}

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

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

	return nil
}

func DeleteSuggestion(s *Suggestion) error {
	transaction, err := DB.Begin()
	if err != nil {
		return err
	}

	// Ensure suggestion hasn't been vetoed
	suggestions, err := VetoedBy(transaction, s)
	if err != nil {
		transaction.Rollback()
		return err
	}
	if len(*suggestions) > 0 {
		transaction.Rollback()
		return SuggestionNotLastError{}
	}

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

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

	return nil
}

func SuggestionHandler(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" {
		suggestion_json := r.PostFormValue("suggestion")
		if suggestion_json == "" {
			WriteError(w, 3 /*Invalid Request*/)
			return
		}

		var suggestion Suggestion
		err := suggestion.Read(suggestion_json)
		if err != nil {
			WriteError(w, 3 /*Invalid Request*/)
			return
		}
		suggestion.SuggestionId = -1
		suggestion.UserId = user.UserId
		suggestion.Date = today

		err = InsertSuggestion(&suggestion)
		if err != nil {
			if _, ok := err.(SuggestionExistsError); ok {
				WriteError(w, 6 /*Suggestion Exists*/)
			} else {
				WriteError(w, 999 /*Internal Error*/)
				log.Print(err)
			}
			return
		}

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

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

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

		suggestion, err := GetSuggestion(suggestionid, user.UserId, today)
		if err != nil {
			WriteError(w, 3 /*Invalid Request*/)
			return
		}

		err = DeleteSuggestion(suggestion)
		if err != nil {
			if _, ok := err.(SuggestionNotLastError); ok {
				WriteError(w, 8 /*Suggestion Not Last*/)
			} else {
				WriteError(w, 999 /*Internal Error*/)
				log.Print(err)
			}
			return
		}

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

func PopularSuggestionHandler(w http.ResponseWriter, r *http.Request) {
	if r.Method == "GET" {
		var sl PopularSuggestionList

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

		sl.PopularSuggestions = suggestions
		err = (&sl).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
	}
}