package main

import (
	"log"
	"sync"
	"time"
)

// TrackedCoin represents a coin we monitor across exchanges.
type TrackedCoin struct {
	Name string // Display name (BTC, ETH, etc.)
	BN   string // Binance symbol (BTCUSDT)
	BG   string // Bitget symbol (BTCUSDT)
	HL   string // HyperLiquid symbol (BTC)
}

// PriceTick holds a price update with optional bid/ask.
type PriceTick struct {
	Price float64
	Bid   float64 // 0 if unknown
	Ask   float64 // 0 if unknown
}

// Spread holds bid/ask data for one exchange+coin.
type Spread struct {
	Bid     float64
	Ask     float64
	Updated int64 // unix nano
}

// PriceStore holds the latest prices from all exchanges, thread-safe.
type PriceStore struct {
	mu       sync.RWMutex
	prices   map[string]map[string]float64 // coin -> exchange -> price
	spreads  map[string]map[string]*Spread // coin -> exchange -> spread
}

func NewPriceStore() *PriceStore {
	return &PriceStore{
		prices:  make(map[string]map[string]float64),
		spreads: make(map[string]map[string]*Spread),
	}
}

// Set stores a price update. If bid/ask are non-zero, also stores spread.
func (s *PriceStore) Set(coin, exchange string, price float64) {
	s.mu.Lock()
	defer s.mu.Unlock()
	if s.prices[coin] == nil {
		s.prices[coin] = make(map[string]float64)
	}
	s.prices[coin][exchange] = price
}

// SetWithSpread stores price + bid/ask spread.
func (s *PriceStore) SetWithSpread(coin, exchange string, price, bid, ask float64) {
	s.mu.Lock()
	defer s.mu.Unlock()
	if s.prices[coin] == nil {
		s.prices[coin] = make(map[string]float64)
	}
	s.prices[coin][exchange] = price

	if bid > 0 && ask > 0 {
		if s.spreads[coin] == nil {
			s.spreads[coin] = make(map[string]*Spread)
		}
		s.spreads[coin][exchange] = &Spread{
			Bid: bid, Ask: ask,
			Updated: time.Now().UnixNano(),
		}
	}
}

func (s *PriceStore) Get(coin, exchange string) (float64, bool) {
	s.mu.RLock()
	defer s.mu.RUnlock()
	p, ok := s.prices[coin][exchange]
	return p, ok
}

// GetSpread returns the current bid-ask spread (as percentage of mid price).
// Returns 0 if no spread data available.
func (s *PriceStore) GetSpread(coin, exchange string) float64 {
	s.mu.RLock()
	defer s.mu.RUnlock()
	sp, ok := s.spreads[coin][exchange]
	if !ok || sp.Bid <= 0 || sp.Ask <= 0 {
		return 0
	}
	mid := (sp.Bid + sp.Ask) / 2
	if mid <= 0 {
		return 0
	}
	return (sp.Ask - sp.Bid) / mid * 100
}

// GetAll returns a snapshot of all prices.
func (s *PriceStore) GetAll() map[string]map[string]float64 {
	s.mu.RLock()
	defer s.mu.RUnlock()
	snap := make(map[string]map[string]float64)
	for coin, exMap := range s.prices {
		snap[coin] = make(map[string]float64)
		for ex, p := range exMap {
			snap[coin][ex] = p
		}
	}
	return snap
}

// ArbOpportunity represents a profitable arbitrage route.
type ArbOpportunity struct {
	Coin       string
	Direction  string // e.g. "BN->HL"
	BuyEx      string
	SellEx     string
	BuyPrice   float64
	SellPrice  float64
	NetProfit  float64 // percentage after fees
	GrossBasis float64 // raw price difference %
}

// SpreadWindow tracks how long each coin's spread stays above threshold.
// Used to measure the window of opportunity between threshold-crossing and
// convergence — helps diagnose whether entry latency is a problem.
type SpreadWindow struct {
	Coin      string
	Direction string // "BG->HL" or "HL->BG"
	Since     time.Time
	PeakNet   float64 // highest netProfit % observed during this window
}

type SpreadWindowTracker struct {
	windows map[string]*SpreadWindow // key: "COIN:DIRECTION"
}

func NewSpreadWindowTracker() *SpreadWindowTracker {
	return &SpreadWindowTracker{windows: make(map[string]*SpreadWindow)}
}

func (swt *SpreadWindowTracker) Tick(snap map[string]map[string]float64, threshold float64) {
	now := time.Now()
	for _, coin := range TrackedCoins {
		exMap := snap[coin.Name]
		if exMap == nil {
			continue
		}
		bgP := exMap[ExBitget]
		hlP := exMap[ExHyperLiquid]
		if bgP <= 0 || hlP <= 0 {
			continue
		}

		// Check both directions — use netProfit() for exact fee model match
		// BG→HL: buy BG (Bitget 0.020%), sell HL (HL 0.015%)
		// HL→BG: buy HL (HL 0.015%), sell BG (Bitget 0.020%)
		type dirCheck struct {
			name      string
			buyPrice  float64
			sellPrice float64
			buyFee    float64
			sellFee   float64
		}
		for _, dir := range []dirCheck{
			{"BG->HL", bgP, hlP, takerFees[ExBitget], takerFees[ExHyperLiquid]},
			{"HL->BG", hlP, bgP, takerFees[ExHyperLiquid], takerFees[ExBitget]},
		} {
			key := coin.Name + ":" + dir.name
			netSpr := netProfit(dir.buyPrice, dir.sellPrice, dir.buyFee, dir.sellFee)

			w, exists := swt.windows[key]
			if netSpr >= threshold {
				if !exists {
					swt.windows[key] = &SpreadWindow{
						Coin:      coin.Name,
						Direction: dir.name,
						Since:     now,
						PeakNet:   netSpr,
					}
				} else if netSpr > w.PeakNet {
					w.PeakNet = netSpr
				}
			} else {
				if exists {
					dur := now.Sub(w.Since)
					if dur > 100*time.Millisecond {
						log.Printf("[SpreadWindow] %s %s exceeded threshold for %v (peak net=%+.4f%%)",
							w.Coin, w.Direction, dur.Round(time.Millisecond), w.PeakNet)
					}
					delete(swt.windows, key)
				}
			}
		}
	}
}