package store

import (
	"context"
	"fmt"
	"strings"
	"time"
)

// LoginRetention is how long a sign-in attempt is kept. Long enough to answer "has this
// television been connecting all month", short enough that the table stays a working
// record rather than an archive nobody prunes. The scheduled housekeeping task reads this
// rather than carrying a number of its own, so the retention lives in one place.
const LoginRetention = 90 * 24 * time.Hour

// Authentication methods. A sign-in is recorded with the route that made it, because
// "this television signed in" and "somebody opened the admin console" are different
// events wearing the same shape, and an operator reading the list must be able to tell
// them apart without inferring it from the device name.
const (
	LoginMethodPassword  = "password"  // a television exchanging Emby credentials
	LoginMethodPIN       = "pin"       // a television recovering a stored device session
	LoginMethodAdmin     = "admin"     // an operator signing into the admin console
	LoginMethodInstaller = "installer" // the web installer's own password check
)

// LoginEvent is one attempt, successful or not.
//
// It is deliberately a *history* rather than a counter on the session row: a session
// carries only the state of the television right now, is overwritten by the next sign-in
// and is deleted when the device is removed — so on its own it can never answer "how many
// times did this set connect today, at what times, and from which addresses". Every field
// here is what was true at the moment of the attempt, including the ones that later move.
type LoginEvent struct {
	ID             int64     `json:"id"`
	OccurredAt     time.Time `json:"occurredAt"`
	EmbyUserID     string    `json:"embyUserId"`
	Username       string    `json:"username"`
	DeviceID       string    `json:"deviceId"`
	DeviceName     string    `json:"deviceName"`
	ClientVersion  string    `json:"clientVersion"`
	ClientProtocol string    `json:"clientProtocol"`
	IPAddress      string    `json:"ipAddress"`
	Success        bool      `json:"success"`
	Method         string    `json:"method"`
	FailureReason  string    `json:"failureReason,omitempty"`
	NewDevice      bool      `json:"newDevice"`
}

// LoginFilter narrows the history. Every field is optional and an unset field is "any",
// so the console's filter bar maps onto it one control per field with no special cases.
type LoginFilter struct {
	EmbyUserID string
	DeviceID   string
	IPAddress  string
	Query      string // free text over username, device name and address
	From       time.Time
	To         time.Time
	Outcome    string // "success" | "failure" | "" for both
	Method     string
	Limit      int
	Offset     int
}

// LoginPage is a window onto the history plus the size of the whole match, so the console
// can page without asking twice and can say "showing 50 of 1,284".
type LoginPage struct {
	Events []LoginEvent `json:"events"`
	Total  int          `json:"total"`
	Limit  int          `json:"limit"`
	Offset int          `json:"offset"`
}

// LoginDeviceSummary is one television's whole relationship with the gateway: how often
// it has signed in, when it last managed to, and how many distinct addresses it has come
// from. This is the row the devices table is built out of.
type LoginDeviceSummary struct {
	DeviceID      string    `json:"deviceId"`
	DeviceName    string    `json:"deviceName"`
	EmbyUserID    string    `json:"embyUserId"`
	Username      string    `json:"username"`
	ClientVersion string    `json:"clientVersion"`
	Logins        int       `json:"logins"`
	Failures      int       `json:"failures"`
	FirstLogin    time.Time `json:"firstLogin"`
	LastLogin     time.Time `json:"lastLogin"`
	LastIP        string    `json:"lastIp"`
	DistinctIPs   int       `json:"distinctIps"`
	LoginsToday   int       `json:"loginsToday"`
}

// LoginDay is one local day's tally. The day is a string rather than a time because it is
// a *label* — the calendar day in the household's zone — and turning it back into an
// instant on the way through the console would invite it being re-formatted in the
// browser's zone instead, which is how a set that connected at 11pm moves to tomorrow.
type LoginDay struct {
	Day      string `json:"day"`
	Logins   int    `json:"logins"`
	Failures int    `json:"failures"`
	Devices  int    `json:"devices"`
}

// LoginAddress is one source address a device or a household has been seen from.
type LoginAddress struct {
	IPAddress string    `json:"ipAddress"`
	Logins    int       `json:"logins"`
	Failures  int       `json:"failures"`
	FirstSeen time.Time `json:"firstSeen"`
	LastSeen  time.Time `json:"lastSeen"`
}

// RecordLogin writes one attempt.
//
// Callers treat a failure here as unimportant: a sign-in that succeeded must not be
// undone because the audit row could not be written, and a sign-in that failed is already
// being refused. It is the caller that decides that, not this function, which is why the
// error is still returned.
func (s *Store) RecordLogin(ctx context.Context, event LoginEvent) error {
	if event.Method == "" {
		event.Method = LoginMethodPassword
	}
	_, err := s.pool.Exec(ctx, `
		INSERT INTO login_events (
			emby_user_id, username, device_id, device_name, client_version,
			client_protocol, ip_address, success, method, failure_reason, new_device
		)
		VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11)`,
		event.EmbyUserID, event.Username, event.DeviceID, event.DeviceName,
		event.ClientVersion, event.ClientProtocol, event.IPAddress, event.Success,
		event.Method, event.FailureReason, event.NewDevice)
	if err != nil {
		return fmt.Errorf("store: record login: %w", err)
	}
	return nil
}

// loginWhere builds the shared predicate. Both the page query and its count run against
// exactly the same clause — derived once rather than written twice, because a filter that
// applied to the rows and not to the total is a table that says "50 of 1,284" over
// something else's total.
func loginWhere(filter LoginFilter) (string, []any) {
	clauses := []string{"TRUE"}
	args := []any{}
	add := func(clause string, value any) {
		args = append(args, value)
		clauses = append(clauses, fmt.Sprintf(clause, len(args)))
	}
	if id := strings.TrimSpace(filter.EmbyUserID); id != "" {
		add("emby_user_id = $%d", id)
	}
	if id := strings.TrimSpace(filter.DeviceID); id != "" {
		add("device_id = $%d", id)
	}
	if ip := strings.TrimSpace(filter.IPAddress); ip != "" {
		add("ip_address = $%d", ip)
	}
	if query := strings.TrimSpace(filter.Query); query != "" {
		add("(username ILIKE '%%' || $%[1]d || '%%'"+
			" OR device_name ILIKE '%%' || $%[1]d || '%%'"+
			" OR ip_address ILIKE '%%' || $%[1]d || '%%')", query)
	}
	if !filter.From.IsZero() {
		add("occurred_at >= $%d", filter.From)
	}
	if !filter.To.IsZero() {
		add("occurred_at < $%d", filter.To)
	}
	switch filter.Outcome {
	case "success":
		clauses = append(clauses, "success")
	case "failure":
		clauses = append(clauses, "NOT success")
	}
	if method := strings.TrimSpace(filter.Method); method != "" {
		add("method = $%d", method)
	}
	return strings.Join(clauses, " AND "), args
}

// LoginEvents answers the filtered history, newest first.
func (s *Store) LoginEvents(ctx context.Context, filter LoginFilter) (LoginPage, error) {
	limit := filter.Limit
	if limit <= 0 || limit > 500 {
		limit = 100
	}
	offset := filter.Offset
	if offset < 0 {
		offset = 0
	}
	where, args := loginWhere(filter)

	page := LoginPage{Events: []LoginEvent{}, Limit: limit, Offset: offset}
	if err := s.pool.QueryRow(ctx,
		`SELECT count(*) FROM login_events WHERE `+where, args...,
	).Scan(&page.Total); err != nil {
		return page, fmt.Errorf("store: count logins: %w", err)
	}

	rows, err := s.pool.Query(ctx, `
		SELECT id, occurred_at, emby_user_id, username, device_id, device_name,
			client_version, client_protocol, ip_address, success, method,
			failure_reason, new_device
		FROM login_events
		WHERE `+where+`
		ORDER BY occurred_at DESC, id DESC
		LIMIT $`+fmt.Sprint(len(args)+1)+` OFFSET $`+fmt.Sprint(len(args)+2),
		append(args, limit, offset)...)
	if err != nil {
		return page, fmt.Errorf("store: list logins: %w", err)
	}
	defer rows.Close()
	for rows.Next() {
		var event LoginEvent
		if err := rows.Scan(
			&event.ID, &event.OccurredAt, &event.EmbyUserID, &event.Username,
			&event.DeviceID, &event.DeviceName, &event.ClientVersion,
			&event.ClientProtocol, &event.IPAddress, &event.Success, &event.Method,
			&event.FailureReason, &event.NewDevice,
		); err != nil {
			return page, fmt.Errorf("store: scan login: %w", err)
		}
		page.Events = append(page.Events, event)
	}
	return page, rows.Err()
}

// LoginDeviceSummaries is the devices table: one row per television the history knows
// about, ordered by how recently it managed to sign in.
//
// It is grouped from the history rather than joined onto sessions on purpose. A set that
// has been removed, or whose session has expired, still connected — and the question this
// page exists to answer is about what happened, not about what is currently valid. The
// session row is what supplies the *current* name and build where one still exists, which
// is why the two are combined here rather than one being preferred outright.
func (s *Store) LoginDeviceSummaries(ctx context.Context, filter LoginFilter, zone string) ([]LoginDeviceSummary, error) {
	where, args := loginWhere(filter)
	args = append(args, zone)
	zoneArg := fmt.Sprintf("$%d", len(args))

	rows, err := s.pool.Query(ctx, `
		WITH history AS (
			SELECT * FROM login_events WHERE `+where+`
		),
		summary AS (
			SELECT device_id,
				count(*) FILTER (WHERE success)                          AS logins,
				count(*) FILTER (WHERE NOT success)                      AS failures,
				min(occurred_at) FILTER (WHERE success)                  AS first_login,
				max(occurred_at) FILTER (WHERE success)                  AS last_login,
				count(DISTINCT ip_address) FILTER (WHERE ip_address <> '') AS distinct_ips,
				count(*) FILTER (
					WHERE success
					  AND (occurred_at AT TIME ZONE `+zoneArg+`)::date
					      = (now() AT TIME ZONE `+zoneArg+`)::date
				) AS logins_today
			FROM history GROUP BY device_id
		),
		latest AS (
			SELECT DISTINCT ON (device_id)
				device_id, emby_user_id, username, device_name, client_version, ip_address
			FROM history
			ORDER BY device_id, occurred_at DESC, id DESC
		)
		SELECT l.device_id,
			COALESCE(s.device_name, l.device_name),
			l.emby_user_id, l.username,
			COALESCE(NULLIF(s.client_version, ''), l.client_version),
			summary.logins, summary.failures,
			summary.first_login, summary.last_login,
			l.ip_address, summary.distinct_ips, summary.logins_today
		FROM latest l
		JOIN summary ON summary.device_id = l.device_id
		LEFT JOIN sessions s
			ON s.device_id = l.device_id AND s.emby_user_id = l.emby_user_id
		ORDER BY summary.last_login DESC NULLS LAST, l.device_id`, args...)
	if err != nil {
		return nil, fmt.Errorf("store: summarise login devices: %w", err)
	}
	defer rows.Close()

	summaries := []LoginDeviceSummary{}
	for rows.Next() {
		var row LoginDeviceSummary
		var first, last *time.Time
		if err := rows.Scan(
			&row.DeviceID, &row.DeviceName, &row.EmbyUserID, &row.Username,
			&row.ClientVersion, &row.Logins, &row.Failures, &first, &last,
			&row.LastIP, &row.DistinctIPs, &row.LoginsToday,
		); err != nil {
			return nil, fmt.Errorf("store: scan login device: %w", err)
		}
		// A device with failures and no successes has no first or last login, which is a
		// real answer and not a zero one — the console prints an em dash for it.
		if first != nil {
			row.FirstLogin = *first
		}
		if last != nil {
			row.LastLogin = *last
		}
		summaries = append(summaries, row)
	}
	return summaries, rows.Err()
}

// LoginDays groups the filtered history by local calendar day, oldest first so the
// console can draw it left to right without reversing it.
//
// The zone is the household's, passed in rather than read here: grouping in UTC would
// move every evening sign-in in New Zealand onto the following day, which is exactly the
// kind of quiet wrongness an operator would never think to question.
func (s *Store) LoginDays(ctx context.Context, filter LoginFilter, zone string) ([]LoginDay, error) {
	where, args := loginWhere(filter)
	args = append(args, zone)
	zoneArg := fmt.Sprintf("$%d", len(args))

	rows, err := s.pool.Query(ctx, `
		SELECT to_char((occurred_at AT TIME ZONE `+zoneArg+`)::date, 'YYYY-MM-DD') AS day,
			count(*) FILTER (WHERE success)     AS logins,
			count(*) FILTER (WHERE NOT success) AS failures,
			count(DISTINCT device_id) FILTER (WHERE success) AS devices
		FROM login_events
		WHERE `+where+`
		GROUP BY day
		ORDER BY day`, args...)
	if err != nil {
		return nil, fmt.Errorf("store: group logins by day: %w", err)
	}
	defer rows.Close()
	days := []LoginDay{}
	for rows.Next() {
		var day LoginDay
		if err := rows.Scan(&day.Day, &day.Logins, &day.Failures, &day.Devices); err != nil {
			return nil, fmt.Errorf("store: scan login day: %w", err)
		}
		days = append(days, day)
	}
	return days, rows.Err()
}

// LoginAddresses is where the filtered attempts came from, busiest first.
func (s *Store) LoginAddresses(ctx context.Context, filter LoginFilter, limit int) ([]LoginAddress, error) {
	if limit <= 0 || limit > 200 {
		limit = 50
	}
	where, args := loginWhere(filter)
	args = append(args, limit)

	rows, err := s.pool.Query(ctx, `
		SELECT ip_address,
			count(*) FILTER (WHERE success)     AS logins,
			count(*) FILTER (WHERE NOT success) AS failures,
			min(occurred_at), max(occurred_at)
		FROM login_events
		WHERE `+where+` AND ip_address <> ''
		GROUP BY ip_address
		ORDER BY count(*) DESC, max(occurred_at) DESC
		LIMIT $`+fmt.Sprint(len(args)), args...)
	if err != nil {
		return nil, fmt.Errorf("store: group logins by address: %w", err)
	}
	defer rows.Close()
	addresses := []LoginAddress{}
	for rows.Next() {
		var address LoginAddress
		if err := rows.Scan(&address.IPAddress, &address.Logins, &address.Failures,
			&address.FirstSeen, &address.LastSeen); err != nil {
			return nil, fmt.Errorf("store: scan login address: %w", err)
		}
		addresses = append(addresses, address)
	}
	return addresses, rows.Err()
}

// LoginTotals is the headline: how the whole filtered window breaks down. It is its own
// query rather than a sum of the page above it, for the reason SearchTotals is — the page
// is a window, and adding it up would report one screenful's total as the household's.
type LoginTotals struct {
	Logins    int       `json:"logins"`
	Failures  int       `json:"failures"`
	Devices   int       `json:"devices"`
	Users     int       `json:"users"`
	Addresses int       `json:"addresses"`
	First     time.Time `json:"first"`
	Last      time.Time `json:"last"`
}

func (s *Store) LoginTotals(ctx context.Context, filter LoginFilter) (LoginTotals, error) {
	where, args := loginWhere(filter)
	var totals LoginTotals
	var first, last *time.Time
	err := s.pool.QueryRow(ctx, `
		SELECT count(*) FILTER (WHERE success),
			count(*) FILTER (WHERE NOT success),
			count(DISTINCT device_id) FILTER (WHERE device_id <> ''),
			count(DISTINCT emby_user_id) FILTER (WHERE emby_user_id <> ''),
			count(DISTINCT ip_address) FILTER (WHERE ip_address <> ''),
			min(occurred_at), max(occurred_at)
		FROM login_events WHERE `+where, args...).
		Scan(&totals.Logins, &totals.Failures, &totals.Devices, &totals.Users,
			&totals.Addresses, &first, &last)
	if err != nil {
		return totals, fmt.Errorf("store: login totals: %w", err)
	}
	if first != nil {
		totals.First = *first
	}
	if last != nil {
		totals.Last = *last
	}
	return totals, nil
}

// DeviceHasLoggedIn reports whether this television has ever successfully signed in
// before. It is what makes "new device registered" a distinguishable event rather than
// one indistinguishable from every subsequent sign-in by the same set — asked before the
// attempt is recorded, so the current sign-in cannot answer for itself.
func (s *Store) DeviceHasLoggedIn(ctx context.Context, embyUserID, deviceID string) (bool, error) {
	if deviceID == "" {
		return true, nil
	}
	var exists bool
	err := s.pool.QueryRow(ctx, `
		SELECT EXISTS (
			SELECT 1 FROM login_events
			WHERE device_id = $1 AND emby_user_id = $2 AND success
		)`, deviceID, embyUserID).Scan(&exists)
	if err != nil {
		return false, fmt.Errorf("store: device login lookup: %w", err)
	}
	return exists, nil
}

// PruneLoginEvents drops attempts older than the retention period. Called by the
// scheduled housekeeping task rather than on the write path: pruning inside a sign-in
// would put a delete over the whole table in front of somebody waiting to watch
// something.
func (s *Store) PruneLoginEvents(ctx context.Context, retention time.Duration) (int64, error) {
	if retention <= 0 {
		retention = LoginRetention
	}
	tag, err := s.pool.Exec(ctx,
		`DELETE FROM login_events WHERE occurred_at < now() - $1::interval`,
		fmt.Sprintf("%d seconds", int64(retention.Seconds())))
	if err != nil {
		return 0, fmt.Errorf("store: prune login events: %w", err)
	}
	return tag.RowsAffected(), nil
}