package account

import (
	"context"
	"errors"
	"fmt"
	"regexp"
	"strings"
	"time"
	"unicode/utf8"

	"github.com/go-jet/jet/v2/postgres"
	"github.com/go-jet/jet/v2/qrm"
	"github.com/google/uuid"

	"scrabble/backend/internal/postgres/jet/backend/model"
	"scrabble/backend/internal/postgres/jet/backend/table"
)

// maxDisplayName caps an editable display name's length in runes (the column itself
// is unbounded; auto-provisioned platform names bypass this editor validation).
const maxDisplayName = 32

// maxAwayWindow bounds the daily away window's duration (midnight-wrap aware).
const maxAwayWindow = 12 * time.Hour

// displayNameRe enforces the editable display-name format (Stage 8): Unicode letters
// joined by single space / "." / "_" separators, where a "." or "_" may be followed
// by a single space. No leading or trailing separator and no two adjacent separators,
// except "<dot|underscore> <space>". So "Name_P. Last" is valid, "Name P._Last" is not.
var displayNameRe = regexp.MustCompile(`^\p{L}+(?:(?:[._] ?| )\p{L}+)*$`)

// ErrInvalidProfile is returned when a profile update carries an unacceptable
// field (an unknown language, an invalid timezone, or an over-long display name).
var ErrInvalidProfile = errors.New("account: invalid profile")

// ProfileUpdate is the full set of player-editable profile fields. UpdateProfile
// overwrites every field, so callers send the complete desired profile. AwayStart
// and AwayEnd carry only the hour and minute of the daily away window, in the
// account's TimeZone.
type ProfileUpdate struct {
	DisplayName            string
	PreferredLanguage      string // "en" or "ru"
	TimeZone               string // an IANA location name
	AwayStart              time.Time
	AwayEnd                time.Time
	BlockChat              bool
	BlockFriendRequests    bool
	NotificationsInAppOnly bool
}

// UpdateProfile validates and overwrites the editable fields of the account, then
// returns the stored row. It reports ErrInvalidProfile for a bad language,
// timezone or display name and ErrNotFound when no account matches id.
func (s *Store) UpdateProfile(ctx context.Context, id uuid.UUID, p ProfileUpdate) (Account, error) {
	lang := strings.TrimSpace(p.PreferredLanguage)
	if lang != "en" && lang != "ru" {
		return Account{}, fmt.Errorf("%w: preferred_language %q", ErrInvalidProfile, p.PreferredLanguage)
	}
	tz := strings.TrimSpace(p.TimeZone)
	if !validZone(tz) {
		return Account{}, fmt.Errorf("%w: time_zone %q", ErrInvalidProfile, p.TimeZone)
	}
	name, err := ValidateDisplayName(p.DisplayName)
	if err != nil {
		return Account{}, err
	}
	if err := validateAwayWindow(p.AwayStart, p.AwayEnd); err != nil {
		return Account{}, err
	}

	stmt := table.Accounts.UPDATE(
		table.Accounts.DisplayName, table.Accounts.PreferredLanguage, table.Accounts.TimeZone,
		table.Accounts.AwayStart, table.Accounts.AwayEnd,
		table.Accounts.BlockChat, table.Accounts.BlockFriendRequests,
		table.Accounts.NotificationsInAppOnly, table.Accounts.UpdatedAt,
	).SET(
		postgres.String(name), postgres.String(lang), postgres.String(tz),
		postgres.TimeT(p.AwayStart), postgres.TimeT(p.AwayEnd),
		postgres.Bool(p.BlockChat), postgres.Bool(p.BlockFriendRequests),
		postgres.Bool(p.NotificationsInAppOnly), postgres.TimestampzT(time.Now().UTC()),
	).WHERE(table.Accounts.AccountID.EQ(postgres.UUID(id))).
		RETURNING(table.Accounts.AllColumns)

	var row model.Accounts
	if err := stmt.QueryContext(ctx, s.db, &row); err != nil {
		if errors.Is(err, qrm.ErrNoRows) {
			return Account{}, ErrNotFound
		}
		return Account{}, fmt.Errorf("account: update profile %s: %w", id, err)
	}
	return modelToAccount(row), nil
}

// ValidateDisplayName trims surrounding whitespace and checks the editable
// display-name length (<= maxDisplayName runes) and format (displayNameRe),
// returning the cleaned name or ErrInvalidProfile. It is exported so the gateway
// boundary could reuse it; the UI mirrors the same rule.
func ValidateDisplayName(raw string) (string, error) {
	name := strings.TrimSpace(raw)
	if name == "" {
		return "", fmt.Errorf("%w: display name is empty", ErrInvalidProfile)
	}
	if utf8.RuneCountInString(name) > maxDisplayName {
		return "", fmt.Errorf("%w: display name exceeds %d characters", ErrInvalidProfile, maxDisplayName)
	}
	if !displayNameRe.MatchString(name) {
		return "", fmt.Errorf("%w: display name has an invalid character or layout", ErrInvalidProfile)
	}
	return name, nil
}

// validateAwayWindow checks that the daily away window's duration, wrapping across
// midnight, does not exceed maxAwayWindow. A zero-length window (start == end) means
// "no away time" and is allowed.
func validateAwayWindow(start, end time.Time) error {
	mins := (end.Hour()*60 + end.Minute()) - (start.Hour()*60 + start.Minute())
	if mins < 0 {
		mins += 24 * 60
	}
	if time.Duration(mins)*time.Minute > maxAwayWindow {
		return fmt.Errorf("%w: away window exceeds %s", ErrInvalidProfile, maxAwayWindow)
	}
	return nil
}