package store

import (
	"context"
	"database/sql"
	"encoding/json"
	"errors"
	"fmt"
	"time"

	"github.com/kristianwind/verdande/internal/auth"
)

type Notification struct {
	ID        string
	UserID    string
	ActorID   string
	ActorName string
	ProjectID string
	TaskID    string
	Kind      string
	Title     string
	Body      string
	ReadAt    *time.Time
	CreatedAt time.Time
}

func (db *DB) CreateNotification(ctx context.Context, n *Notification) error {
	if n.ID == "" {
		n.ID = NewID()
	}
	n.CreatedAt = time.Now().UTC()

	_, err := db.ExecContext(ctx,
		`INSERT INTO notifications (id, user_id, actor_id, project_id, task_id, kind,
		                            title, body, created_at)
		 VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)`,
		n.ID, n.UserID, nullString(n.ActorID), nullString(n.ProjectID),
		nullString(n.TaskID), n.Kind, n.Title, n.Body, n.CreatedAt.Unix())
	return err
}

func (db *DB) ListNotifications(ctx context.Context, userID string, limit int) ([]Notification, error) {
	if limit <= 0 || limit > 100 {
		limit = 30
	}
	rows, err := db.QueryContext(ctx, `
		SELECT n.id, n.user_id, n.actor_id, COALESCE(u.name, ''), n.project_id, n.task_id,
		       n.kind, n.title, n.body, n.read_at, n.created_at
		FROM notifications n
		LEFT JOIN users u ON u.id = n.actor_id
		WHERE n.user_id = ?
		ORDER BY n.created_at DESC
		LIMIT ?`, userID, limit)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	out := []Notification{}
	for rows.Next() {
		var n Notification
		var actorID, projectID, taskID sql.NullString
		var readAt sql.NullInt64
		var created int64
		if err := rows.Scan(&n.ID, &n.UserID, &actorID, &n.ActorName, &projectID,
			&taskID, &n.Kind, &n.Title, &n.Body, &readAt, &created); err != nil {
			return nil, err
		}
		n.ActorID, n.ProjectID, n.TaskID = actorID.String, projectID.String, taskID.String
		if readAt.Valid {
			v := time.Unix(readAt.Int64, 0).UTC()
			n.ReadAt = &v
		}
		n.CreatedAt = time.Unix(created, 0).UTC()
		out = append(out, n)
	}
	return out, rows.Err()
}

func (db *DB) UnreadNotificationCount(ctx context.Context, userID string) (int, error) {
	var n int
	err := db.QueryRowContext(ctx,
		`SELECT count(*) FROM notifications WHERE user_id = ? AND read_at IS NULL`,
		userID).Scan(&n)
	return n, err
}

// MarkNotificationsRead marks one, or all of them when id is empty.
func (db *DB) MarkNotificationsRead(ctx context.Context, userID, id string) error {
	query := `UPDATE notifications SET read_at = ? WHERE user_id = ? AND read_at IS NULL`
	args := []any{time.Now().Unix(), userID}
	if id != "" {
		query += ` AND id = ?`
		args = append(args, id)
	}
	_, err := db.ExecContext(ctx, query, args...)
	return err
}

// ProjectMemberIDs is everyone who can see a project, owner included — the audience
// for a notification about something that happened inside it.
func (db *DB) ProjectMemberIDs(ctx context.Context, projectID string) ([]string, error) {
	rows, err := db.QueryContext(ctx, `
		SELECT owner_id FROM projects WHERE id = ?
		UNION
		SELECT user_id FROM project_members WHERE project_id = ?`, projectID, projectID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var out []string
	for rows.Next() {
		var id string
		if err := rows.Scan(&id); err != nil {
			return nil, err
		}
		out = append(out, id)
	}
	return out, rows.Err()
}

// --- Web Push subscriptions --------------------------------------------------------

type PushSubscription struct {
	ID        string
	UserID    string
	Endpoint  string
	P256dh    string
	Auth      string
	UserAgent string
	Failures  int
}

// SavePushSubscription is an upsert on the endpoint: a browser that re-subscribes
// produces the same endpoint, and a second row would mean two identical
// notifications on one device.
func (db *DB) SavePushSubscription(ctx context.Context, sub *PushSubscription) error {
	if sub.ID == "" {
		sub.ID = NewID()
	}
	// The upsert no longer moves the row between accounts.
	//
	// `user_id = excluded.user_id` was in the DO UPDATE, so anybody who learned
	// another person's endpoint could claim it by subscribing with it: the
	// victim's device would then receive the claimant's notifications and none of
	// its own. A re-subscribe from the same person still refreshes the keys, which
	// is what the upsert is actually for.
	_, err := db.ExecContext(ctx,
		`INSERT INTO push_subscriptions (id, user_id, endpoint, p256dh, auth, user_agent, created_at)
		 VALUES (?, ?, ?, ?, ?, ?, ?)
		 ON CONFLICT (endpoint) DO UPDATE SET
		     p256dh = excluded.p256dh,
		     auth = excluded.auth,
		     user_agent = excluded.user_agent,
		     failures = 0`,
		sub.ID, sub.UserID, sub.Endpoint, sub.P256dh, sub.Auth, sub.UserAgent,
		time.Now().Unix())
	return err
}

func (db *DB) ListPushSubscriptions(ctx context.Context, userID string) ([]PushSubscription, error) {
	rows, err := db.QueryContext(ctx,
		`SELECT id, user_id, endpoint, p256dh, auth, user_agent, failures
		 FROM push_subscriptions WHERE user_id = ?`, userID)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	out := []PushSubscription{}
	for rows.Next() {
		var s PushSubscription
		if err := rows.Scan(&s.ID, &s.UserID, &s.Endpoint, &s.P256dh, &s.Auth,
			&s.UserAgent, &s.Failures); err != nil {
			return nil, err
		}
		out = append(out, s)
	}
	return out, rows.Err()
}

// DeletePushSubscription removes one of this person's devices.
//
// Scoped by user as well as by endpoint. It was endpoint alone, which meant
// anybody who learned somebody else's endpoint could silently unsubscribe their
// phone — and the endpoint is the only thing about a subscription that ever
// leaves the browser.
func (db *DB) DeletePushSubscription(ctx context.Context, userID, endpoint string) error {
	_, err := db.ExecContext(ctx,
		`DELETE FROM push_subscriptions WHERE endpoint = ? AND user_id = ?`, endpoint, userID)
	return err
}

// dropPushEndpoint removes a subscription the push service has declared dead.
// Unexported so the only *request* path to a delete stays the scoped one.
func (db *DB) dropPushEndpoint(ctx context.Context, endpoint string) error {
	_, err := db.ExecContext(ctx, `DELETE FROM push_subscriptions WHERE endpoint = ?`, endpoint)
	return err
}

// RecordPushFailure counts a delivery failure and drops the subscription once it
// has failed enough times. A push service says 404 or 410 when an endpoint is gone,
// but it also has bad days — forgiving a few failures keeps a flaky network from
// silently unsubscribing somebody's phone.
func (db *DB) RecordPushFailure(ctx context.Context, endpoint string, permanent bool) error {
	if permanent {
		// Not scoped by user, and that is right here: this is the push service
		// saying the endpoint is gone, not a person asking for something. There is
		// no caller to check against — the caller is the delivery job.
		return db.dropPushEndpoint(ctx, endpoint)
	}
	_, err := db.ExecContext(ctx,
		`UPDATE push_subscriptions SET failures = failures + 1 WHERE endpoint = ?`, endpoint)
	if err != nil {
		return err
	}
	_, err = db.ExecContext(ctx,
		`DELETE FROM push_subscriptions WHERE endpoint = ? AND failures >= 10`, endpoint)
	return err
}

// --- VAPID keypair ------------------------------------------------------------------

// InstanceKeys returns the VAPID keypair, generating it on first use.
//
// Generated rather than configured: it identifies this instance to push services
// and is not something an operator should have to produce. Rotating it only costs
// every browser re-subscribing.
func (db *DB) InstanceKeys(ctx context.Context, generate func() (public, private string, err error)) (string, string, error) {
	var public, private string
	err := db.QueryRowContext(ctx,
		`SELECT public_key, private_key FROM instance_keys LIMIT 1`).Scan(&public, &private)
	if err == nil {
		return public, private, nil
	}
	if err != sql.ErrNoRows {
		return "", "", err
	}

	public, private, err = generate()
	if err != nil {
		return "", "", err
	}
	_, err = db.ExecContext(ctx,
		`INSERT INTO instance_keys (id, public_key, private_key, created_at) VALUES (?, ?, ?, ?)`,
		NewID(), public, private, time.Now().Unix())
	if err != nil {
		// Another request generated one first; take theirs so the two agree.
		var existingPub, existingPriv string
		if qErr := db.QueryRowContext(ctx,
			`SELECT public_key, private_key FROM instance_keys LIMIT 1`).
			Scan(&existingPub, &existingPriv); qErr == nil {
			return existingPub, existingPriv, nil
		}
		return "", "", err
	}
	return public, private, nil
}

// --- mail-to-task tokens -------------------------------------------------------------

func (db *DB) EnsureMailToken(ctx context.Context, userID string) (string, error) {
	var token sql.NullString
	err := db.QueryRowContext(ctx, `SELECT mail_token FROM users WHERE id = ?`, userID).Scan(&token)
	if err != nil {
		return "", err
	}
	if token.Valid && token.String != "" {
		return token.String, nil
	}

	fresh, err := auth.NewToken()
	if err != nil {
		return "", err
	}
	if err := db.SetMailToken(ctx, userID, fresh); err != nil {
		return "", err
	}
	return fresh, nil
}

func (db *DB) SetMailToken(ctx context.Context, userID, token string) error {
	_, err := db.ExecContext(ctx,
		`UPDATE users SET mail_token = ?, updated_at = ? WHERE id = ?`,
		token, time.Now().Unix(), userID)
	return err
}

func (db *DB) UserByMailToken(ctx context.Context, token string) (*User, error) {
	if token == "" {
		return nil, ErrNotFound
	}
	return db.scanUser(ctx, `SELECT `+userColumns+` FROM users WHERE mail_token = ?`, token)
}

// --- per-user settings ------------------------------------------------------------------

// UserSettings reads one scope of a person's integration settings. A missing row is
// an empty map, not an error: nobody has settings until they set some.
// --- sealed values ----------------------------------------------------------------

// secretFields are the keys whose values never leave this process in the clear.
//
// A named set rather than "seal everything": the rest of a settings blob is what
// somebody reads when a mailbox misbehaves — which folder, which label, which
// address — and turning all of it into ciphertext would buy nothing and cost the
// ability to look.
var secretFields = map[string]bool{
	"refresh_token": true,
	"access_token":  true,
	"password":      true,
	"client_secret": true,
	// The AI provider's key. Missed when this list was written, and it is exactly
	// the same kind of thing as the rest: a live credential, in a settings blob,
	// in a database anybody with a backup file can read. Existing rows convert
	// themselves the next time the settings are saved.
	"api_key": true,
}

// seal returns a copy of values with the secret fields sealed. Without a key it
// returns them untouched, which is what the tests that never set one expect.
func (db *DB) seal(values map[string]any) (map[string]any, error) {
	if db.box == nil {
		return values, nil
	}
	out := make(map[string]any, len(values))
	for k, v := range values {
		s, ok := v.(string)
		if !secretFields[k] || !ok {
			out[k] = v
			continue
		}
		sealed, err := db.box.Seal(s)
		if err != nil {
			return nil, fmt.Errorf("seal %s: %w", k, err)
		}
		out[k] = sealed
	}
	return out, nil
}

// unseal is seal's other direction. Values written before there was a key come
// back as themselves; the next write puts them away properly, so the column
// converts itself as it is used rather than in one migration that has to be right
// about every row at once.
func (db *DB) unseal(values map[string]any) (map[string]any, error) {
	if db.box == nil {
		return values, nil
	}
	for k, v := range values {
		s, ok := v.(string)
		if !secretFields[k] || !ok {
			continue
		}
		plain, err := db.box.Unseal(s)
		if err != nil {
			return nil, fmt.Errorf("read %s: %w", k, err)
		}
		values[k] = plain
	}
	return values, nil
}

func (db *DB) UserSettings(ctx context.Context, userID, scope string) (map[string]any, error) {
	var raw string
	err := db.QueryRowContext(ctx,
		`SELECT values_json FROM user_settings WHERE user_id = ? AND scope = ?`,
		userID, scope).Scan(&raw)
	if err == sql.ErrNoRows {
		return map[string]any{}, nil
	}
	if err != nil {
		return nil, err
	}

	values := map[string]any{}
	if err := json.Unmarshal([]byte(raw), &values); err != nil {
		return map[string]any{}, nil
	}
	return db.unseal(values)
}

func (db *DB) SetUserSettings(ctx context.Context, userID, scope string, values map[string]any) error {
	values, err := db.seal(values)
	if err != nil {
		return err
	}
	raw, err := json.Marshal(values)
	if err != nil {
		return err
	}
	_, err = db.ExecContext(ctx, `
		INSERT INTO user_settings (user_id, scope, values_json, updated_at)
		VALUES (?, ?, ?, ?)
		ON CONFLICT (user_id) DO UPDATE SET
		    scope = excluded.scope,
		    values_json = excluded.values_json,
		    updated_at = excluded.updated_at`,
		userID, scope, string(raw), time.Now().Unix())
	return err
}

// --- instance-wide settings -------------------------------------------------------------

// InstanceSettings reads one scope of the instance's own settings. A missing row
// is an empty map, not an error.
//
// Separate from UserSettings because some configuration is the server's rather
// than a person's — the Gmail OAuth client is one registration that everybody
// connecting a mailbox goes through, not a preference each of them holds.
func (db *DB) InstanceSettings(ctx context.Context, scope string) (map[string]any, error) {
	var raw string
	err := db.QueryRowContext(ctx,
		`SELECT values_json FROM instance_settings WHERE scope = ?`, scope).Scan(&raw)
	if errors.Is(err, sql.ErrNoRows) {
		return map[string]any{}, nil
	}
	if err != nil {
		return nil, err
	}
	values := map[string]any{}
	if err := json.Unmarshal([]byte(raw), &values); err != nil {
		return map[string]any{}, nil
	}
	return db.unseal(values)
}

func (db *DB) SetInstanceSettings(ctx context.Context, scope string, values map[string]any) error {
	values, err := db.seal(values)
	if err != nil {
		return err
	}
	raw, err := json.Marshal(values)
	if err != nil {
		return err
	}
	_, err = db.ExecContext(ctx, `
		INSERT INTO instance_settings (scope, values_json, updated_at)
		VALUES (?, ?, ?)
		ON CONFLICT (scope) DO UPDATE SET
		    values_json = excluded.values_json,
		    updated_at = excluded.updated_at`,
		scope, string(raw), time.Now().Unix())
	return err
}