package main

import (
	"database/sql"
	"math/rand/v2"
	"net/http"
	"os"
	"time"

	"github.com/go-chi/chi/v5"
	"golang.org/x/crypto/bcrypt"
)

func createUser(username, password string) error {
	uid := int64(rand.IntN(99999999))
	now := time.Now().Unix()

	hash, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
	if err != nil {
		return err
	}

	_, err = db.Exec(
		`INSERT INTO user (uid, created_at, username, password) VALUES (?, ?, ?, ?)`,
		uid, now, username, hash,
	)
	return err
}

// idFromUsername liefert die interne id oder 0, wenn der Nutzer nicht existiert.
func idFromUsername(username string) int64 {
	var id int64
	if err := db.QueryRow(`SELECT id FROM user WHERE username = ?`, username).Scan(&id); err != nil {
		return 0
	}
	return id
}

func handleUserPage(w http.ResponseWriter, r *http.Request) {
	username := chi.URLParam(r, "username")

	var uid, createdAt int64
	err := db.QueryRow(`SELECT uid, created_at FROM user WHERE username = ?`, username).Scan(&uid, &createdAt)
	if err != nil {
		writeError(w, http.StatusNotFound, "Nutzer nicht gefunden")
		return
	}
	writeJSON(w, http.StatusOK, map[string]any{
		"uid":        uid,
		"username":   username,
		"created_at": createdAt,
	})
}

func handleUserInfo(w http.ResponseWriter, r *http.Request) {
	uid := uidFromContext(r.Context())

	var createdAt, lastLogin sql.NullInt64
	var username string
	err := db.QueryRow(
		`SELECT created_at, last_login, username FROM user WHERE uid = ?`, uid,
	).Scan(&createdAt, &lastLogin, &username)
	if err != nil {
		writeError(w, http.StatusNotFound, "Nutzer nicht gefunden")
		return
	}
	writeJSON(w, http.StatusOK, map[string]any{
		"uid":        uid,
		"username":   username,
		"created_at": createdAt.Int64,
		"last_login": lastLogin.Int64,
	})
}

// handleUserDelete löscht den eingeloggten Account dauerhaft, nach Bestätigung
// durch das Passwort (Formularfeld pass1). Beiträge, Votes und Sessions werden
// in einer Transaktion mitgelöscht; zugehörige Mediendateien best effort entfernt.
func handleUserDelete(w http.ResponseWriter, r *http.Request) {
	uid := uidFromContext(r.Context())

	var hash []byte
	if err := db.QueryRow(`SELECT password FROM user WHERE uid = ?`, uid).Scan(&hash); err != nil {
		writeError(w, http.StatusNotFound, "Nutzer nicht gefunden")
		return
	}

	if bcrypt.CompareHashAndPassword(hash, []byte(r.FormValue("pass1"))) != nil {
		writeError(w, http.StatusForbidden, "Passwort ist falsch.")
		return
	}

	// Mediendateien der Beiträge einsammeln, bevor die Zeilen verschwinden.
	var media []string
	if rows, err := db.Query(`SELECT filepath FROM entry WHERE uid = ?`, uid); err == nil {
		for rows.Next() {
			var fp string
			if rows.Scan(&fp) == nil && fp != "" {
				media = append(media, fp)
			}
		}
		rows.Close()
	}

	tx, err := db.Begin()
	if err != nil {
		writeError(w, http.StatusInternalServerError, "Löschen fehlgeschlagen")
		return
	}
	for _, q := range []string{
		`DELETE FROM session WHERE uid = ?`,
		`DELETE FROM vote WHERE uid = ?`,
		`DELETE FROM entry WHERE uid = ?`,
		`DELETE FROM user WHERE uid = ?`,
	} {
		if _, err := tx.Exec(q, uid); err != nil {
			tx.Rollback()
			writeError(w, http.StatusInternalServerError, "Löschen fehlgeschlagen")
			return
		}
	}
	if err := tx.Commit(); err != nil {
		writeError(w, http.StatusInternalServerError, "Löschen fehlgeschlagen")
		return
	}

	// Erst nach erfolgreichem Commit die Dateien entfernen.
	for _, fp := range media {
		os.Remove(fp)
	}

	http.SetCookie(w, &http.Cookie{
		Name:    "session",
		Value:   "",
		Path:    "/",
		Expires: time.Unix(0, 0),
		MaxAge:  -1,
	})
	writeJSON(w, http.StatusOK, map[string]string{"status": "deleted"})
}