package storage

import (
	"context"
	"database/sql"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"time"

	_ "modernc.org/sqlite"
)

var (
	db          *sql.DB
	initOnce    sync.Once
	initErr     error
	defaultPath = "fail2ban-ui.db"
)

func boolToInt(b bool) int {
	if b {
		return 1
	}
	return 0
}

func intToBool(i int) bool {
	return i != 0
}

func stringFromNull(ns sql.NullString) string {
	if ns.Valid {
		return ns.String
	}
	return ""
}

func intFromNull(ni sql.NullInt64) int {
	if ni.Valid {
		return int(ni.Int64)
	}
	return 0
}

type AppSettingsRecord struct {
	Language           string
	Port               int
	Debug              bool
	CallbackURL        string
	RestartNeeded      bool
	AlertCountriesJSON string
	SMTPHost           string
	SMTPPort           int
	SMTPUsername       string
	SMTPPassword       string
	SMTPFrom           string
	SMTPUseTLS         bool
	BantimeIncrement   bool
	IgnoreIP           string
	Bantime            string
	Findtime           string
	MaxRetry           int
	DestEmail          string
}

type ServerRecord struct {
	ID           string
	Name         string
	Type         string
	Host         string
	Port         int
	SocketPath   string
	LogPath      string
	SSHUser      string
	SSHKeyPath   string
	AgentURL     string
	AgentSecret  string
	Hostname     string
	TagsJSON     string
	IsDefault    bool
	Enabled      bool
	NeedsRestart bool
	CreatedAt    time.Time
	UpdatedAt    time.Time
}

// BanEventRecord represents a single ban event stored in the internal database.
type BanEventRecord struct {
	ID         int64     `json:"id"`
	ServerID   string    `json:"serverId"`
	ServerName string    `json:"serverName"`
	Jail       string    `json:"jail"`
	IP         string    `json:"ip"`
	Country    string    `json:"country"`
	Hostname   string    `json:"hostname"`
	Failures   string    `json:"failures"`
	Whois      string    `json:"whois"`
	Logs       string    `json:"logs"`
	OccurredAt time.Time `json:"occurredAt"`
	CreatedAt  time.Time `json:"createdAt"`
}

// RecurringIPStat represents aggregation info for repeatedly banned IPs.
type RecurringIPStat struct {
	IP       string    `json:"ip"`
	Country  string    `json:"country"`
	Count    int64     `json:"count"`
	LastSeen time.Time `json:"lastSeen"`
}

// Init initializes the internal storage. Safe to call multiple times.
func Init(dbPath string) error {
	initOnce.Do(func() {
		if dbPath == "" {
			dbPath = defaultPath
		}
		if err := ensureDirectory(dbPath); err != nil {
			initErr = err
			return
		}

		var err error
		db, err = sql.Open("sqlite", fmt.Sprintf("file:%s?_pragma=journal_mode(WAL)&_pragma=busy_timeout=5000", dbPath))
		if err != nil {
			initErr = err
			return
		}

		if err = db.Ping(); err != nil {
			initErr = err
			return
		}

		initErr = ensureSchema(context.Background())
	})
	return initErr
}

// Close closes the underlying database if it has been initialised.
func Close() error {
	if db == nil {
		return nil
	}
	return db.Close()
}

func GetAppSettings(ctx context.Context) (AppSettingsRecord, bool, error) {
	if db == nil {
		return AppSettingsRecord{}, false, errors.New("storage not initialised")
	}

	row := db.QueryRowContext(ctx, `
SELECT language, port, debug, callback_url, restart_needed, alert_countries, smtp_host, smtp_port, smtp_username, smtp_password, smtp_from, smtp_use_tls, bantime_increment, ignore_ip, bantime, findtime, maxretry, destemail
FROM app_settings
WHERE id = 1`)

	var (
		lang, callback, alerts, smtpHost, smtpUser, smtpPass, smtpFrom, ignoreIP, bantime, findtime, destemail sql.NullString
		port, smtpPort, maxretry                                                                               sql.NullInt64
		debug, restartNeeded, smtpTLS, bantimeInc                                                              sql.NullInt64
	)

	err := row.Scan(&lang, &port, &debug, &callback, &restartNeeded, &alerts, &smtpHost, &smtpPort, &smtpUser, &smtpPass, &smtpFrom, &smtpTLS, &bantimeInc, &ignoreIP, &bantime, &findtime, &maxretry, &destemail)
	if errors.Is(err, sql.ErrNoRows) {
		return AppSettingsRecord{}, false, nil
	}
	if err != nil {
		return AppSettingsRecord{}, false, err
	}

	rec := AppSettingsRecord{
		Language:           stringFromNull(lang),
		Port:               intFromNull(port),
		Debug:              intToBool(intFromNull(debug)),
		CallbackURL:        stringFromNull(callback),
		RestartNeeded:      intToBool(intFromNull(restartNeeded)),
		AlertCountriesJSON: stringFromNull(alerts),
		SMTPHost:           stringFromNull(smtpHost),
		SMTPPort:           intFromNull(smtpPort),
		SMTPUsername:       stringFromNull(smtpUser),
		SMTPPassword:       stringFromNull(smtpPass),
		SMTPFrom:           stringFromNull(smtpFrom),
		SMTPUseTLS:         intToBool(intFromNull(smtpTLS)),
		BantimeIncrement:   intToBool(intFromNull(bantimeInc)),
		IgnoreIP:           stringFromNull(ignoreIP),
		Bantime:            stringFromNull(bantime),
		Findtime:           stringFromNull(findtime),
		MaxRetry:           intFromNull(maxretry),
		DestEmail:          stringFromNull(destemail),
	}

	return rec, true, nil
}

func SaveAppSettings(ctx context.Context, rec AppSettingsRecord) error {
	if db == nil {
		return errors.New("storage not initialised")
	}
	_, err := db.ExecContext(ctx, `
INSERT INTO app_settings (
	id, language, port, debug, callback_url, restart_needed, alert_countries, smtp_host, smtp_port, smtp_username, smtp_password, smtp_from, smtp_use_tls, bantime_increment, ignore_ip, bantime, findtime, maxretry, destemail
) VALUES (
	1, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?
) ON CONFLICT(id) DO UPDATE SET
	language = excluded.language,
	port = excluded.port,
	debug = excluded.debug,
	callback_url = excluded.callback_url,
	restart_needed = excluded.restart_needed,
	alert_countries = excluded.alert_countries,
	smtp_host = excluded.smtp_host,
	smtp_port = excluded.smtp_port,
	smtp_username = excluded.smtp_username,
	smtp_password = excluded.smtp_password,
	smtp_from = excluded.smtp_from,
	smtp_use_tls = excluded.smtp_use_tls,
	bantime_increment = excluded.bantime_increment,
	ignore_ip = excluded.ignore_ip,
	bantime = excluded.bantime,
	findtime = excluded.findtime,
	maxretry = excluded.maxretry,
	destemail = excluded.destemail
`, rec.Language,
		rec.Port,
		boolToInt(rec.Debug),
		rec.CallbackURL,
		boolToInt(rec.RestartNeeded),
		rec.AlertCountriesJSON,
		rec.SMTPHost,
		rec.SMTPPort,
		rec.SMTPUsername,
		rec.SMTPPassword,
		rec.SMTPFrom,
		boolToInt(rec.SMTPUseTLS),
		boolToInt(rec.BantimeIncrement),
		rec.IgnoreIP,
		rec.Bantime,
		rec.Findtime,
		rec.MaxRetry,
		rec.DestEmail,
	)
	return err
}

func ListServers(ctx context.Context) ([]ServerRecord, error) {
	if db == nil {
		return nil, errors.New("storage not initialised")
	}

	rows, err := db.QueryContext(ctx, `
SELECT id, name, type, host, port, socket_path, log_path, ssh_user, ssh_key_path, agent_url, agent_secret, hostname, tags, is_default, enabled, needs_restart, created_at, updated_at
FROM servers
ORDER BY created_at`)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var records []ServerRecord
	for rows.Next() {
		var rec ServerRecord
		var host, socket, logPath, sshUser, sshKey, agentURL, agentSecret, hostname, tags sql.NullString
		var name, serverType sql.NullString
		var created, updated sql.NullString
		var port sql.NullInt64
		var isDefault, enabled, needsRestart sql.NullInt64

		if err := rows.Scan(
			&rec.ID,
			&name,
			&serverType,
			&host,
			&port,
			&socket,
			&logPath,
			&sshUser,
			&sshKey,
			&agentURL,
			&agentSecret,
			&hostname,
			&tags,
			&isDefault,
			&enabled,
			&needsRestart,
			&created,
			&updated,
		); err != nil {
			return nil, err
		}

		rec.Name = stringFromNull(name)
		rec.Type = stringFromNull(serverType)
		rec.Host = stringFromNull(host)
		rec.Port = intFromNull(port)
		rec.SocketPath = stringFromNull(socket)
		rec.LogPath = stringFromNull(logPath)
		rec.SSHUser = stringFromNull(sshUser)
		rec.SSHKeyPath = stringFromNull(sshKey)
		rec.AgentURL = stringFromNull(agentURL)
		rec.AgentSecret = stringFromNull(agentSecret)
		rec.Hostname = stringFromNull(hostname)
		rec.TagsJSON = stringFromNull(tags)
		rec.IsDefault = intToBool(intFromNull(isDefault))
		rec.Enabled = intToBool(intFromNull(enabled))
		rec.NeedsRestart = intToBool(intFromNull(needsRestart))

		if created.Valid {
			if t, err := time.Parse(time.RFC3339Nano, created.String); err == nil {
				rec.CreatedAt = t
			}
		}
		if updated.Valid {
			if t, err := time.Parse(time.RFC3339Nano, updated.String); err == nil {
				rec.UpdatedAt = t
			}
		}

		records = append(records, rec)
	}

	return records, rows.Err()
}

func ReplaceServers(ctx context.Context, servers []ServerRecord) error {
	if db == nil {
		return errors.New("storage not initialised")
	}

	tx, err := db.BeginTx(ctx, nil)
	if err != nil {
		return err
	}
	defer func() {
		if err != nil {
			_ = tx.Rollback()
		}
	}()

	if _, err = tx.ExecContext(ctx, `DELETE FROM servers`); err != nil {
		return err
	}

	stmt, err := tx.PrepareContext(ctx, `
INSERT INTO servers (
	id, name, type, host, port, socket_path, log_path, ssh_user, ssh_key_path, agent_url, agent_secret, hostname, tags, is_default, enabled, needs_restart, created_at, updated_at
) VALUES (
	?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?
)`)
	if err != nil {
		return err
	}
	defer stmt.Close()

	for _, srv := range servers {
		createdAt := srv.CreatedAt
		if createdAt.IsZero() {
			createdAt = time.Now().UTC()
		}
		updatedAt := srv.UpdatedAt
		if updatedAt.IsZero() {
			updatedAt = createdAt
		}
		if _, err = stmt.ExecContext(ctx,
			srv.ID,
			srv.Name,
			srv.Type,
			srv.Host,
			srv.Port,
			srv.SocketPath,
			srv.LogPath,
			srv.SSHUser,
			srv.SSHKeyPath,
			srv.AgentURL,
			srv.AgentSecret,
			srv.Hostname,
			srv.TagsJSON,
			boolToInt(srv.IsDefault),
			boolToInt(srv.Enabled),
			boolToInt(srv.NeedsRestart),
			createdAt.Format(time.RFC3339Nano),
			updatedAt.Format(time.RFC3339Nano),
		); err != nil {
			return err
		}
	}

	err = tx.Commit()
	return err
}

func DeleteServer(ctx context.Context, id string) error {
	if db == nil {
		return errors.New("storage not initialised")
	}
	_, err := db.ExecContext(ctx, `DELETE FROM servers WHERE id = ?`, id)
	return err
}

// RecordBanEvent stores a ban event in the database.
func RecordBanEvent(ctx context.Context, record BanEventRecord) error {
	if db == nil {
		return errors.New("storage not initialised")
	}

	if record.ServerID == "" {
		return errors.New("server id is required")
	}
	now := time.Now().UTC()
	if record.CreatedAt.IsZero() {
		record.CreatedAt = now
	}
	if record.OccurredAt.IsZero() {
		record.OccurredAt = now
	}

	const query = `
INSERT INTO ban_events (
	server_id, server_name, jail, ip, country, hostname, failures, whois, logs, occurred_at, created_at
) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`

	_, err := db.ExecContext(
		ctx,
		query,
		record.ServerID,
		record.ServerName,
		record.Jail,
		record.IP,
		record.Country,
		record.Hostname,
		record.Failures,
		record.Whois,
		record.Logs,
		record.OccurredAt.UTC(),
		record.CreatedAt.UTC(),
	)
	return err
}

// ListBanEvents returns ban events ordered by creation date descending.
func ListBanEvents(ctx context.Context, serverID string, limit int, since time.Time) ([]BanEventRecord, error) {
	if db == nil {
		return nil, errors.New("storage not initialised")
	}

	if limit <= 0 || limit > 500 {
		limit = 100
	}

	baseQuery := `
SELECT id, server_id, server_name, jail, ip, country, hostname, failures, whois, logs, occurred_at, created_at
FROM ban_events
WHERE 1=1`

	args := []any{}
	if serverID != "" {
		baseQuery += " AND server_id = ?"
		args = append(args, serverID)
	}
	if !since.IsZero() {
		baseQuery += " AND occurred_at >= ?"
		args = append(args, since.UTC())
	}

	baseQuery += " ORDER BY occurred_at DESC LIMIT ?"
	args = append(args, limit)

	rows, err := db.QueryContext(ctx, baseQuery, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var results []BanEventRecord
	for rows.Next() {
		var rec BanEventRecord
		if err := rows.Scan(
			&rec.ID,
			&rec.ServerID,
			&rec.ServerName,
			&rec.Jail,
			&rec.IP,
			&rec.Country,
			&rec.Hostname,
			&rec.Failures,
			&rec.Whois,
			&rec.Logs,
			&rec.OccurredAt,
			&rec.CreatedAt,
		); err != nil {
			return nil, err
		}
		results = append(results, rec)
	}

	return results, rows.Err()
}

// CountBanEventsByServer returns simple aggregation per server.
func CountBanEventsByServer(ctx context.Context, since time.Time) (map[string]int64, error) {
	if db == nil {
		return nil, errors.New("storage not initialised")
	}

	query := `
SELECT server_id, COUNT(*) 
FROM ban_events
WHERE 1=1`
	args := []any{}

	if !since.IsZero() {
		query += " AND occurred_at >= ?"
		args = append(args, since.UTC())
	}

	query += " GROUP BY server_id"

	rows, err := db.QueryContext(ctx, query, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	result := make(map[string]int64)
	for rows.Next() {
		var serverID string
		var count int64
		if err := rows.Scan(&serverID, &count); err != nil {
			return nil, err
		}
		result[serverID] = count
	}

	return result, rows.Err()
}

// CountBanEvents returns total number of ban events optionally filtered by time.
func CountBanEvents(ctx context.Context, since time.Time) (int64, error) {
	if db == nil {
		return 0, errors.New("storage not initialised")
	}

	query := `
SELECT COUNT(*)
FROM ban_events
WHERE 1=1`
	args := []any{}

	if !since.IsZero() {
		query += " AND occurred_at >= ?"
		args = append(args, since.UTC())
	}

	var total int64
	if err := db.QueryRowContext(ctx, query, args...).Scan(&total); err != nil {
		return 0, err
	}
	return total, nil
}

// CountBanEventsByCountry returns aggregation per country code.
func CountBanEventsByCountry(ctx context.Context, since time.Time) (map[string]int64, error) {
	if db == nil {
		return nil, errors.New("storage not initialised")
	}

	query := `
SELECT COALESCE(country, '') AS country, COUNT(*)
FROM ban_events
WHERE 1=1`
	args := []any{}

	if !since.IsZero() {
		query += " AND occurred_at >= ?"
		args = append(args, since.UTC())
	}

	query += " GROUP BY COALESCE(country, '')"

	rows, err := db.QueryContext(ctx, query, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	result := make(map[string]int64)
	for rows.Next() {
		var country sql.NullString
		var count int64
		if err := rows.Scan(&country, &count); err != nil {
			return nil, err
		}
		result[stringFromNull(country)] = count
	}

	return result, rows.Err()
}

// ListRecurringIPStats returns IPs that have been banned at least minCount times.
func ListRecurringIPStats(ctx context.Context, since time.Time, minCount, limit int) ([]RecurringIPStat, error) {
	if db == nil {
		return nil, errors.New("storage not initialised")
	}

	if minCount < 2 {
		minCount = 2
	}
	if limit <= 0 || limit > 500 {
		limit = 100
	}

	query := `
SELECT ip, COALESCE(country, '') AS country, COUNT(*) AS cnt, MAX(occurred_at) AS last_seen
FROM ban_events
WHERE ip != ''`
	args := []any{}

	if !since.IsZero() {
		query += " AND occurred_at >= ?"
		args = append(args, since.UTC())
	}

	query += `
GROUP BY ip, COALESCE(country, '')
HAVING cnt >= ?
ORDER BY cnt DESC, last_seen DESC
LIMIT ?`

	args = append(args, minCount, limit)

	rows, err := db.QueryContext(ctx, query, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var results []RecurringIPStat
	for rows.Next() {
		var stat RecurringIPStat
		var lastSeen sql.NullString
		if err := rows.Scan(&stat.IP, &stat.Country, &stat.Count, &lastSeen); err != nil {
			return nil, err
		}
		if lastSeen.Valid {
			if parsed, err := time.Parse(time.RFC3339Nano, lastSeen.String); err == nil {
				stat.LastSeen = parsed
			}
		}
		results = append(results, stat)
	}

	return results, rows.Err()
}

func ensureSchema(ctx context.Context) error {
	if db == nil {
		return errors.New("storage not initialised")
	}

	const createTable = `
CREATE TABLE IF NOT EXISTS app_settings (
	id INTEGER PRIMARY KEY CHECK (id = 1),
	language TEXT,
	port INTEGER,
	debug INTEGER,
	callback_url TEXT,
	restart_needed INTEGER,
	alert_countries TEXT,
	smtp_host TEXT,
	smtp_port INTEGER,
	smtp_username TEXT,
	smtp_password TEXT,
	smtp_from TEXT,
	smtp_use_tls INTEGER,
	bantime_increment INTEGER,
	ignore_ip TEXT,
	bantime TEXT,
	findtime TEXT,
	maxretry INTEGER,
	destemail TEXT
);

CREATE TABLE IF NOT EXISTS servers (
	id TEXT PRIMARY KEY,
	name TEXT,
	type TEXT,
	host TEXT,
	port INTEGER,
	socket_path TEXT,
	log_path TEXT,
	ssh_user TEXT,
	ssh_key_path TEXT,
	agent_url TEXT,
	agent_secret TEXT,
	hostname TEXT,
	tags TEXT,
	is_default INTEGER,
	enabled INTEGER,
	needs_restart INTEGER DEFAULT 0,
	created_at TEXT,
	updated_at TEXT
);

CREATE TABLE IF NOT EXISTS ban_events (
	id INTEGER PRIMARY KEY AUTOINCREMENT,
	server_id TEXT NOT NULL,
	server_name TEXT NOT NULL,
	jail TEXT NOT NULL,
	ip TEXT NOT NULL,
	country TEXT,
	hostname TEXT,
	failures TEXT,
	whois TEXT,
	logs TEXT,
	occurred_at DATETIME NOT NULL,
	created_at DATETIME NOT NULL
);

CREATE INDEX IF NOT EXISTS idx_ban_events_server_id ON ban_events(server_id);
CREATE INDEX IF NOT EXISTS idx_ban_events_occurred_at ON ban_events(occurred_at);
`

	if _, err := db.ExecContext(ctx, createTable); err != nil {
		return err
	}

	// Backfill needs_restart column for existing databases that predate it.
	if _, err := db.ExecContext(ctx, `ALTER TABLE servers ADD COLUMN needs_restart INTEGER DEFAULT 0`); err != nil {
		if !strings.Contains(strings.ToLower(err.Error()), "duplicate column name") {
			return err
		}
	}

	return nil
}

func ensureDirectory(path string) error {
	if path == ":memory:" {
		return nil
	}
	dir := filepath.Dir(path)
	if dir == "." || dir == "" {
		return nil
	}
	return os.MkdirAll(dir, 0o755)
}