package main

import (
	"database/sql"
	"encoding/json"
	"fmt"
	"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 handleGetPing(w http.ResponseWriter, r *http.Request) {
	log.Printf("[*] Received request %v %v\n", r.Method, r.URL)
	fmt.Fprintf(w, "PONG\n")
}

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 /api/ping",
		handleGetPing,
	)

	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(
		"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)
	}
}