nextjs-app/src/lib/technical/support-resistance.ts

import type { Candle, SRLevel } from './types'

export function findSupportResistance(candles: Candle[], numLevels = 6): SRLevel[] {
  if (candles.length < 20) return []
  const levels: SRLevel[] = []
  const tolerance = 0.015 // 1.5%

  // Find local peaks and troughs (using 5-bar window)
  const peaks: number[] = []
  const troughs: number[] = []
  for (let i = 2; i < candles.length - 2; i++) {
    const c = candles[i]
    if (c.high >= candles[i - 1].high && c.high >= candles[i - 2].high &&
        c.high >= candles[i + 1].high && c.high >= candles[i + 2].high) {
      peaks.push(c.high)
    }
    if (c.low <= candles[i - 1].low && c.low <= candles[i - 2].low &&
        c.low <= candles[i + 1].low && c.low <= candles[i + 2].low) {
      troughs.push(c.low)
    }
  }

  // Cluster nearby peaks/troughs
  function cluster(arr: number[]): { price: number; count: number }[] {
    if (!arr.length) return []
    const sorted = [...arr].sort((a, b) => a - b)
    const clusters: { prices: number[]; sum: number }[] = []
    for (const p of sorted) {
      let found = false
      for (const c of clusters) {
        const avg = c.sum / c.prices.length
        if (Math.abs(p - avg) / avg < tolerance) {
          c.prices.push(p); c.sum += p; found = true; break
        }
      }
      if (!found) clusters.push({ prices: [p], sum: p })
    }
    return clusters
      .map((c) => ({ price: c.sum / c.prices.length, count: c.prices.length }))
      .sort((a, b) => b.count - a.count)
  }

  const lastPrice = candles[candles.length - 1].close

  for (const { price, count } of cluster(troughs).slice(0, numLevels)) {
    if (price < lastPrice) {
      levels.push({ price, type: 'support', strength: Math.min(5, count), touches: count })
    }
  }
  for (const { price, count } of cluster(peaks).slice(0, numLevels)) {
    if (price > lastPrice) {
      levels.push({ price, type: 'resistance', strength: Math.min(5, count), touches: count })
    }
  }

  return levels.sort((a, b) => a.price - b.price).slice(0, numLevels)
}