nextjs-app/src/lib/formatters.ts

/**
 * Centralized formatting utilities for consistent display across the app.
 * Solves F-M3 (inconsistent dates) and F-M4 (inconsistent numbers).
 */

// ─── Number Formatting ────────────────────────────

const trLocale = 'tr-TR'
const usLocale = 'en-US'

function loc(market?: 'bist' | 'us') { return market === 'us' ? usLocale : trLocale }

/**
 * Format a price value with 2 decimal places.
 * e.g. 1234.56 → "1.234,56" (BIST) or "1,234.56" (US)
 */
export function formatPrice(value: number | null | undefined, currency = '₺', market?: 'bist' | 'us'): string {
  if (value == null || !Number.isFinite(value)) return '—'
  const formatted = value.toLocaleString(loc(market), {
    minimumFractionDigits: 2,
    maximumFractionDigits: 2,
  })
  return currency ? `${currency}${formatted}` : formatted
}

/**
 * Format a price without currency symbol for charts/tables.
 */
export function formatNumber(value: number | null | undefined, decimals = 2, market?: 'bist' | 'us'): string {
  if (value == null || !Number.isFinite(value)) return '—'
  return value.toLocaleString(loc(market), {
    minimumFractionDigits: decimals,
    maximumFractionDigits: decimals,
  })
}

/**
 * Format a percentage value with sign.
 * e.g. 5.678 → "+5,68%", -3.2 → "-3,20%"
 */
export function formatPercent(value: number | null | undefined, decimals = 2, market?: 'bist' | 'us'): string {
  if (value == null || !Number.isFinite(value)) return '—'
  const sign = value > 0 ? '+' : ''
  return `${sign}${value.toLocaleString(loc(market), {
    minimumFractionDigits: decimals,
    maximumFractionDigits: decimals,
  })}%`
}

/**
 * Format large numbers with abbreviations.
 * e.g. 1500000 → "1,5M", 2300 → "2,3K"
 */
export function formatCompact(value: number | null | undefined, market?: 'bist' | 'us'): string {
  if (value == null || !Number.isFinite(value)) return '—'
  const abs = Math.abs(value)
  const sign = value < 0 ? '-' : ''
  const l = loc(market)

  if (abs >= 1_000_000_000) {
    return `${sign}${(abs / 1_000_000_000).toLocaleString(l, { maximumFractionDigits: 1 })}B`
  }
  if (abs >= 1_000_000) {
    return `${sign}${(abs / 1_000_000).toLocaleString(l, { maximumFractionDigits: 1 })}M`
  }
  if (abs >= 1_000) {
    return `${sign}${(abs / 1_000).toLocaleString(l, { maximumFractionDigits: 1 })}K`
  }
  return value.toLocaleString(l, { maximumFractionDigits: 0 })
}

/**
 * Format volume (shares traded).
 */
export function formatVolume(value: number | null | undefined): string {
  return formatCompact(value)
}

// ─── Date Formatting ──────────────────────────────

/**
 * Format a date string or Date object.
 * e.g. "2025-01-15" → "15 Oca 2025" (BIST) or "Jan 15, 2025" (US)
 */
export function formatDate(date: string | Date | null | undefined, market?: 'bist' | 'us'): string {
  if (!date) return '—'
  try {
    const d = typeof date === 'string' ? new Date(date) : date
    if (isNaN(d.getTime())) return '—'
    return d.toLocaleDateString(loc(market), {
      day: 'numeric',
      month: 'short',
      year: 'numeric',
    })
  } catch {
    return '—'
  }
}

/**
 * Format a date with time.
 */
export function formatDateTime(date: string | Date | null | undefined, market?: 'bist' | 'us'): string {
  if (!date) return '—'
  try {
    const d = typeof date === 'string' ? new Date(date) : date
    if (isNaN(d.getTime())) return '—'
    return d.toLocaleDateString(loc(market), {
      day: 'numeric',
      month: 'short',
      year: 'numeric',
      hour: '2-digit',
      minute: '2-digit',
    })
  } catch {
    return '—'
  }
}

/**
 * Relative time formatting.
 */
export function formatRelativeTime(date: string | Date | null | undefined, market?: 'bist' | 'us'): string {
  if (!date) return '—'
  try {
    const d = typeof date === 'string' ? new Date(date) : date
    if (isNaN(d.getTime())) return '—'

    const now = Date.now()
    const diffMs = now - d.getTime()
    const diffSec = Math.floor(diffMs / 1000)
    const diffMin = Math.floor(diffSec / 60)
    const diffHours = Math.floor(diffMin / 60)
    const diffDays = Math.floor(diffHours / 24)

    const isUS = market === 'us'
    if (diffSec < 60) return isUS ? 'Just now' : 'Az önce'
    if (diffMin < 60) return isUS ? `${diffMin}m ago` : `${diffMin} dakika önce`
    if (diffHours < 24) return isUS ? `${diffHours}h ago` : `${diffHours} saat önce`
    if (diffDays < 7) return isUS ? `${diffDays}d ago` : `${diffDays} gün önce`
    if (diffDays < 30) return isUS ? `${Math.floor(diffDays / 7)}w ago` : `${Math.floor(diffDays / 7)} hafta önce`
    return formatDate(d, market)
  } catch {
    return '—'
  }
}