package main

import (
	"database/sql"
	"encoding/json"
	"html/template"
	"log"
	"net/http"
	"strconv"

	_ "github.com/mattn/go-sqlite3"
)

const (
	PORT    = "8080"
	DB_FILE = "./datefinder.sqlite3"
)

var (
	db                *sql.DB
	indexHtmlTemplate *template.Template
)

type ChoicesPost struct {
	PollId   int      `json:"pollId"`
	Username string   `json:"username"`
	Choices  [][]bool `json:"choices"`
}

func initDatabase() {
	var err error
	db, err = sql.Open("sqlite3", DB_FILE)
	if err != nil {
		log.Fatalf("[!] Could not open database file %s, error: %s\n", DB_FILE, err)
	}

	const createPollsQuery = `
		CREATE TABLE IF NOT EXISTS polls (
			id INTEGER PRIMARY KEY AUTOINCREMENT,
			name TEXT NOT NULL
		);
	`

	_, err = db.Exec(createPollsQuery)
	if err != nil {
		log.Fatalf("[!] Could not create database table polls, error: %s\n", err)
	}

	const createChoicesQuery = `
		CREATE TABLE IF NOT EXISTS choices (
			id INTEGER PRIMARY KEY AUTOINCREMENT,
			pollid INTEGER NOT NULL,
			username TEXT NOT NULL,
			choices TEXT NOT NULL,
			FOREIGN KEY(pollid) REFERENCES polls(id)
		);
	`

	_, err = db.Exec(createChoicesQuery)
	if err != nil {
		log.Fatalf("[!] Could not create database table choices, error: %s\n", err)
	}
}

func prepareStaticContent() {
	var err error
	indexHtmlTemplate, err = template.ParseFiles("./static/index.html.tmpl")
	if err != nil {
		log.Fatalf("[!] Could not parse index.html template, error: %s\n", err)
	}
}

func handleGetRoot(w http.ResponseWriter, r *http.Request) {
	var pollName string
	pollId, err := strconv.Atoi(r.PathValue("pollId"))
	if err != nil {
		log.Printf("[!] Invallid poll id url segment, error: %s\n", err)
		http.Error(w, "Poll not found", http.StatusBadRequest)
		return
	}

	const query = `
		SELECT name
		FROM polls
		WHERE id = ?;
	`

	err = db.QueryRow(query, pollId).Scan(&pollName)
	if err != nil {
		log.Printf("[!] No poll with id %d was found, error: %s\n", pollId, err)
		http.Error(w, "Poll not found", http.StatusBadRequest)
		return
	}

	err = indexHtmlTemplate.Execute(w, struct {
		PollId   int
		PollName string
	}{
		PollId:   pollId,
		PollName: pollName,
	})
	if err != nil {
		log.Printf("[!] Could not execute index.html template, error: %s\n", err)
		http.Error(w, "Error rendering template", http.StatusInternalServerError)
	}
}

func handleGetResult(w http.ResponseWriter, r *http.Request) {
	pollId, err := strconv.Atoi(r.PathValue("pollId"))
	if err != nil {
		log.Printf("[!] Invallid poll id url segment, error: %s\n", err)
		http.Error(w, "Poll not found", http.StatusBadRequest)
		return
	}

	const query = `
		SELECT polls.name, choices.username, choices.choices
		FROM choices
		JOIN polls ON choices.pollid = polls.id
		WHERE choices.pollid = ?
	`

	rows, err := db.Query(query, pollId)
	defer rows.Close()
	if err != nil {
		log.Printf("[!] No poll with id %d was found, error: %s\n", pollId, err)
		http.Error(w, "Poll not found", http.StatusBadRequest)
		return
	}

	var results []struct {
		pollName string
		username string
		choices  string
	}
	for rows.Next() {
		var pollName string
		var username string
		var choices string
		if err := rows.Scan(&pollName, &username, &choices); err != nil {
			log.Printf("[!] Could not scan result row %v, error: %s\n", rows, err)
		}
		results = append(results, struct {
			pollName string
			username string
			choices  string
		}{
			pollName: pollName,
			username: username,
			choices:  choices,
		})
	}

	type HourlyVote struct {
		Usernames []string `json:"usernames"`
		Votes     int      `json:"votes"`
	}

	type PollResult struct {
		Id    int               `json:"id"`
		Name  string            `json:"name"`
		Votes [7][24]HourlyVote `json:"votes"`
	}

	var pollResult PollResult

	pollResult.Id = pollId
	pollResult.Name = results[0].pollName

	for i := 0; i < 7; i++ {
		for j := 0; j < 24; j++ {
			pollResult.Votes[i][j] = HourlyVote{
				Usernames: []string{},
				Votes:     0,
			}
		}
	}

	for _, result := range results {
		var choices [][]bool
		err := json.Unmarshal([]byte(result.choices), &choices)
		if err != nil {
			log.Printf("[!] Could not unmarshal choices %s, error: %s\n", result.choices, err)
			continue
		}

		for didx, day := range choices {
			for hidx, hour := range day {
				if hour {
					pollResult.Votes[didx][hidx].Usernames =
						append(pollResult.Votes[didx][hidx].Usernames, result.username)
					pollResult.Votes[didx][hidx].Votes++
				}
			}
		}
	}

	w.Header().Set("Content-Type", "application/json")
	if err := json.NewEncoder(w).Encode(pollResult); err != nil {
		http.Error(w, "Failed to encode JSON", http.StatusInternalServerError)
	}
}

func handlePostSubmit(w http.ResponseWriter, r *http.Request) {
	log.Printf("[*] Received request %v %v\n", r.Method, r.URL)
	log.Printf("[*] %v\n", r.Body)

	w.Header().Set("Access-Control-Allow-Origin", "*")
	w.Header().Set("Access-Control-Allow-Methods", "OPTIONS, GET, POST")
	w.Header().Set("Access-Control-Allow-Headers", "Content-Type, Access-Control-Allow-Origin")

	var choicesPost ChoicesPost

	err := json.NewDecoder(r.Body).Decode(&choicesPost)
	if err != nil {
		log.Printf("[!] Error decoding request Body %v, error: %s\n", r.Body, err)
		w.WriteHeader(http.StatusBadRequest)
		return
	}

	choicesJson, err := json.Marshal(choicesPost.Choices)
	if err != nil {
		log.Printf("[!] Could not marshal choices, error: %s\n", err)
	}

	tx, err := db.Begin()
	if err != nil {
		log.Printf("[!] Could not begin database transaction, error: %s\n", err)
		w.WriteHeader(http.StatusBadRequest)
		return
	}

	const query = `
		INSERT INTO choices (pollid, username, choices)
		VALUES (?, ?, ?);
	`

	_, err = tx.Exec(query, choicesPost.PollId, choicesPost.Username, string(choicesJson))
	if err != nil {
		log.Printf("[!] Could not insert choices into database, error: %s\n", err)
		tx.Rollback()
		w.WriteHeader(http.StatusBadRequest)
		return
	}
	tx.Commit()

	log.Printf("[*] Persisted choices for poll %d, username %s to database\n",
		choicesPost.PollId, choicesPost.Username)

	w.WriteHeader(http.StatusOK)
}

func handleOptionsSubmit(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Access-Control-Allow-Origin", "*")
	w.Header().Set("Access-Control-Allow-Methods", "OPTIONS, GET, POST")
	w.Header().Set("Access-Control-Allow-Headers", "Content-Type, Access-Control-Allow-Origin")
	w.WriteHeader(http.StatusNoContent)
}

func main() {
	initDatabase()
	defer db.Close()

	prepareStaticContent()

	http.HandleFunc(
		"GET /favicon.ico",
		func(w http.ResponseWriter, r *http.Request) {
			http.Error(w, "There is no favicon.ico!", http.StatusBadRequest)
		},
	)

	http.HandleFunc(
		"GET /{pollId}",
		handleGetRoot,
	)

	http.HandleFunc(
		"GET /{pollId}/result",
		handleGetResult,
	)

	http.HandleFunc(
		"POST /api/submit",
		handlePostSubmit,
	)

	http.HandleFunc(
		"OPTIONS /api/submit",
		handleOptionsSubmit,
	)

	log.Printf("[*] Datefinder server listening on :%s\n", PORT)
	if err := http.ListenAndServe(":8080", nil); err != nil {
		log.Fatalf("[!] Could not start server on %s, error: %s\n", PORT, err)
	}
}