package main

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

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

var db *sql.DB

type Note struct {
	Id      int64  `json:"id"`
	Content string `json:"content"`
}

func httpError(err error, statusCode int, message string, w http.ResponseWriter) bool {
	if err != nil {
		log.Println(err)
		writeError(w, statusCode, message)
		return true
	}

	return false
}

func writeError(w http.ResponseWriter, statusCode int, message string) {
	type errorResponse struct {
		Message string `json:"message"`
	}

	response := errorResponse{Message: message}
	json, err := json.Marshal(response)
	if err != nil {
		return
	}

	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(statusCode)
	w.Write(json)
}

func getNotes(w http.ResponseWriter, req *http.Request, _ httprouter.Params) {
	res, err := db.Query(`SELECT Id, Content FROM Notes`)
	if httpError(err, http.StatusInternalServerError, "Failed to load notes", w) {
		return
	}

	defer res.Close()

	var notes []Note = []Note{}

	for res.Next() {
		if httpError(res.Err(), http.StatusInternalServerError, "Failed to load notes", w) {
			return
		}

		var note Note
		res.Scan(&note.Id, &note.Content)
		notes = append(notes, note)
	}

	json, err := json.Marshal(notes)
	if httpError(err, http.StatusInternalServerError, "Failed to create JSON", w) {
		return
	}

	w.Header().Set("Content-Type", "application/json")
	w.Write(json)
}

func postNotes(w http.ResponseWriter, req *http.Request, _ httprouter.Params) {
	data, err := io.ReadAll(req.Body)
	if httpError(err, http.StatusBadRequest, "Failed to read data", w) {
		return
	}

	var note Note
	err = json.Unmarshal(data, &note)
	if httpError(err, http.StatusBadRequest, "Invalid request", w) {
		return
	}

	if len(note.Content) == 0 {
		writeError(w, http.StatusBadRequest, "Missing note content")
		return
	}

	stmt, err := db.Prepare(`INSERT INTO Notes(Content) VALUES(?) RETURNING Id`)
	if httpError(err, http.StatusInternalServerError, "Failed to store note", w) {
		return
	}

	defer stmt.Close()

	res := stmt.QueryRow(note.Content)
	err = res.Scan(&note.Id)
	if httpError(err, http.StatusInternalServerError, "Failed to store note", w) {
		return
	}

	json, err := json.Marshal(note)
	if httpError(err, http.StatusInternalServerError, "Failed to create JSON", w) {
		return
	}

	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusCreated)
	w.Write(json)
}

func getNote(w http.ResponseWriter, req *http.Request, p httprouter.Params) {
	id, err := strconv.ParseInt(p.ByName("id"), 10, 64)
	if httpError(err, http.StatusBadRequest, "Invalid id", w) {
		return
	}

	stmt, err := db.Prepare(`SELECT Content FROM Notes WHERE Id = ?`)
	if httpError(err, http.StatusInternalServerError, "Failed to get note", w) {
		return
	}

	defer stmt.Close()

	res := stmt.QueryRow(id)

	var note Note = Note{Id: id}

	err = res.Scan(&note.Content)
	if err == sql.ErrNoRows {
		writeError(w, http.StatusNotFound, "Note doesn't exist")
		return
	}

	if httpError(err, http.StatusInternalServerError, "Failed to get note", w) {
		return
	}

	json, err := json.Marshal(note)
	if httpError(err, http.StatusInternalServerError, "Failed to create JSON", w) {
		return
	}

	w.Header().Set("Content-Type", "application/json")
	w.Write(json)
}

func putNote(w http.ResponseWriter, req *http.Request, p httprouter.Params) {
	id, err := strconv.ParseInt(p.ByName("id"), 10, 64)
	if httpError(err, http.StatusBadRequest, "Invalid id", w) {
		return
	}

	data, err := io.ReadAll(req.Body)
	if httpError(err, http.StatusBadRequest, "Failed to read data", w) {
		return
	}

	var note Note
	err = json.Unmarshal(data, &note)
	if httpError(err, http.StatusBadRequest, "Invalid request", w) {
		return
	}

	if len(note.Content) == 0 {
		writeError(w, http.StatusBadRequest, "Missing note content")
		return
	}

	stmt, err := db.Prepare(`UPDATE Notes SET Content = ? WHERE Id = ?`)
	if httpError(err, http.StatusInternalServerError, "Failed to update note", w) {
		return
	}

	defer stmt.Close()

	res, err := stmt.Exec(note.Content, id)
	if httpError(err, http.StatusInternalServerError, "Failed to update note", w) {
		return
	}

	updated, err := res.RowsAffected()
	if httpError(err, http.StatusInternalServerError, "Failed to update note", w) {
		return
	}

	if updated == 0 {
		writeError(w, http.StatusNotFound, "Note doesn't exist")
		return
	}

	note.Id = id
	json, err := json.Marshal(note)
	if httpError(err, http.StatusInternalServerError, "Failed to create JSON", w) {
		return
	}

	w.Header().Set("Content-Type", "application/json")
	w.Write(json)
}

func main() {
	log.Println("Starting NoteServer")

	log.Println("Loading database")

	var err error
	db, err = sql.Open("sqlite3", "./notes.sqlite")
	if err != nil {
		log.Fatalln("Failed to load db:", err)
	}

	log.Println("Creating missing tables")
	_, err = db.Exec(`CREATE TABLE IF NOT EXISTS Notes(Id INTEGER PRIMARY KEY AUTOINCREMENT, Content TEXT)`)
	if err != nil {
		log.Fatalln("Failed to create table:", err)
	}

	log.Println("Listening")

	router := httprouter.New()
	router.GET("/api/notes", getNotes)
	router.POST("/api/notes", postNotes)
	router.GET("/api/note/:id", getNote)
	router.PUT("/api/note/:id", putNote)

	http.ListenAndServe(":8080", router) // TODO: configure host, port, TLS
}