// peertube-instance-index-filter
// Copyright (C) 2025 Arns Udovič <zordsdavini@arns.lt>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

package main

import (
	"database/sql"
	"strconv"
	"time"

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

var migrations = []string{
	"SELECT 1;",
	"ALTER TABLE instances ADD COLUMN rejected INTEGER NOT NULL DEFAULT 0;",
	"ALTER TABLE instances ADD COLUMN reject_reason TEXT;",
	"ALTER TABLE index_host ADD COLUMN instance_url TEXT;",
}

type IndexHost struct {
	Url string
	InstanceUrl string
	LastFetchedAt string
}

func connectDB() *sql.DB {
	db, err := sql.Open("sqlite3", "./instances.db")
	if err != nil {
		panic(err)
	}

	checkPreinstall(db)

	return db
}

func checkPreinstall(db *sql.DB) {
	sqlStmt := `
		CREATE TABLE IF NOT EXISTS instances (
			id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,
			url TEXT NOT NULL,
			data TEXT NOT NULL,
			created_at TEXT NOT NULL
		);

		CREATE INDEX IF NOT EXISTS idx_instances_url ON instances (created_at);

		CREATE TABLE IF NOT EXISTS index_host (
			id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,
			url TEXT NOT NULL,
			last_fetched_at TEXT NOT NULL
		);

		CREATE TABLE IF NOT EXISTS counter (
			id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,
			key TEXT NOT NULL,
			counter INTEGER NOT NULL
		);

		CREATE UNIQUE INDEX IF NOT EXISTS idx_counter_key ON counter (key);

		INSERT OR IGNORE INTO counter (key, counter) VALUES ('last_migration', 0);
	`

	_, err := db.Exec(sqlStmt)
	if err != nil {
		panic(err)
	}

	runMigrations(db)
}

func runMigrations(db *sql.DB) {
	lastMigratuion, err := getCounter(db, "last_migration")
	if err != nil {
		panic(err)
	}

	for i := lastMigratuion; i < len(migrations); i++ {
		_, err := db.Exec(migrations[i])
		if err != nil {
			panic(err)
		}

		db.Exec("UPDATE counter SET counter = counter+1 WHERE key = 'last_migration';")
	}
}

func getCounter(db *sql.DB, key string) (int, error) {
	var counter int
	err := db.QueryRow("SELECT counter FROM counter WHERE key = ?", key).Scan(&counter)

	return counter, err
}

func indexExists(db *sql.DB, url string) (bool, error) {
	var count int
	err := db.QueryRow("SELECT COUNT(*) FROM index_host WHERE url = ?", url).Scan(&count)
	return count > 0, err
}

func addIndex(db *sql.DB, indexHost IndexHost) {
	db.Exec("INSERT INTO index_host (url, instance_url, last_fetched_at) VALUES (?, ?, '2000-01-01');", indexHost.Url, indexHost.InstanceUrl)
}

func rejectHost(db *sql.DB, host string, reason string) {
	db.Exec("UPDATE instances SET rejected = 1, reject_reason = ? WHERE url = ?", reason, host)
}

func getIndexHosts(db *sql.DB) []IndexHost {
	indexHosts := []IndexHost{}
	rows, err := db.Query("SELECT url, instance_url, last_fetched_at FROM index_host")
	if err != nil {
		panic(err)
	}

	for rows.Next() {
		var indexHost IndexHost
		rows.Scan(&indexHost.Url, &indexHost.InstanceUrl, &indexHost.LastFetchedAt)
		indexHosts = append(indexHosts, indexHost)
	}

	return indexHosts
}

func updateLastFetched(db *sql.DB, indexHost IndexHost) {
	db.Exec("UPDATE index_host SET last_fetched_at = ? WHERE url = ?", time.Now().Add(-24*time.Hour).Format("2006-01-02"), indexHost.Url)
}

func addInstance(db *sql.DB, instance Instance) {
	var count int
	db.QueryRow("SELECT COUNT(*) FROM instance WHERE url = ?", instance.Url).Scan(&count)

	if count > 0 {
		return
	}
	
	db.Exec("INSERT INTO instances (url, data, created_at) VALUES (?, ?, ?);", instance.Url, instance.Data, instance.CreatedAt)
}

func getHosts(db *sql.DB, start int, count int, since string, search string, property string) ([]string, error) {
	hosts := []string{}
	query := "SELECT " + property + " FROM instances WHERE rejected = 0"
	if since != "" {
		query += " AND created_at > \"" + since + "\""
	}
	if search != "" {
		query += " AND url LIKE \"%" + search + "%\""
	}
	rows, err := db.Query(query + " ORDER BY created_at DESC LIMIT ? OFFSET ?", count, start)
	if err != nil {
		return hosts, err
	}

	for rows.Next() {
		var host string
		rows.Scan(&host)
		hosts = append(hosts, host)
	}

	return hosts, nil
}

func getHostsTotal(db *sql.DB, since string, search string) (int, error) {
	total := "0"
	query := "SELECT count(url) FROM instances WHERE rejected = 0"
	if since != "" {
		query += " AND created_at > \"" + since + "\""
	}
	if search != "" {
		query += " AND url LIKE \"%" + search + "%\""
	}

	row := db.QueryRow(query)
	row.Scan(&total)

	totali, err := strconv.Atoi(total)
	if err != nil {
		return 0, err
	}

	return totali, nil
}

func getRejectedHostsTotal(db *sql.DB) (int, error) {
	total := "0"
	query := "SELECT count(url) FROM instances WHERE rejected = 1"

	row := db.QueryRow(query)
	row.Scan(&total)

	totali, err := strconv.Atoi(total)
	if err != nil {
		return 0, err
	}

	return totali, nil
}

func getDuplicateIds(db *sql.DB) ([]string, error) {
	ids := []string{}
	query := "SELECT id FROM instances GROUP BY url HAVING COUNT(*) > 1"
	rows, err := db.Query(query)
	if err != nil {
		return ids, err
	}

	for rows.Next() {
		var id string
		rows.Scan(&id)
		ids = append(ids, id)
	}

	return ids, nil
}

func removeInstance(db *sql.DB, id string) {
	db.Exec("DELETE FROM instances WHERE id = ?", id)
}