package exchange

import (
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
	"math"
	"math/big"
	"net/http"
	"strings"
	"sync"
	"time"

	"crypto/ed25519"
	"crypto/sha512"
)

// HLOrderAction represents a HyperLiquid order action.
type HLOrderAction struct {
	Type       string `json:"type"`
	Order      HLOrder `json:"order"`
	Grouping   string `json:"grouping"`
	BrokerCode int    `json:"brokerCode"`
}

type HLOrder struct {
	Coin    string `json:"coin"`
	IsBuy   bool   `json:"isBuy"`
	Sz      string `json:"sz"`
	LimitPx string `json:"limitPx"`
	OrderType string `json:"orderType"`
	ReduceOnly bool `json:"reduceOnly"`
}

// HLSignedAction wraps the action with signature.
type HLSignedAction struct {
	Action      HLOrderAction `json:"action"`
	Nonce       int64         `json:"nonce"`
	Signature   string        `json:"signature"`
	VaultAddress string       `json:"vaultAddress,omitempty"`
}

type HLOrderResponse struct {
	Response *json.RawMessage `json:"response"`
	Data     *json.RawMessage `json:"data"`
}

// HyperLiquidTrade handles order placement on HyperLiquid.
type HyperLiquidTrade struct {
	PrivateKey ed25519.PrivateKey
	Address    string
	client     *http.Client
	lastNonce  int64
	nonceMu    sync.Mutex // protect lastNonce++ (Issue #4)
}

func NewHyperLiquidTrade(privateKeyHex, address string) (*HyperLiquidTrade, error) {
	if privateKeyHex == "" {
		return &HyperLiquidTrade{client: &http.Client{Timeout: 10 * time.Second}}, nil
	}
	keyBytes, err := hex.DecodeString(privateKeyHex)
	if err != nil {
		return nil, fmt.Errorf("decode private key: %w", err)
	}
	if len(keyBytes) != ed25519.PrivateKeySize {
		return nil, fmt.Errorf("invalid private key length: %d (expected %d)", len(keyBytes), ed25519.PrivateKeySize)
	}
	return &HyperLiquidTrade{
		PrivateKey: ed25519.PrivateKey(keyBytes),
		Address:    address,
		client:     &http.Client{Timeout: 10 * time.Second},
	}, nil
}

func (h *HyperLiquidTrade) IsConfigured() bool {
	return h.PrivateKey != nil && h.Address != ""
}

// PlaceMarketOrder places a market order on HyperLiquid.
// coin: "BTC", side: "buy" or "sell", sz: order size in coin units (e.g. "0.001")
func (h *HyperLiquidTrade) PlaceMarketOrder(coin, side, sz string) (string, error) {
	if !h.IsConfigured() {
		return "", fmt.Errorf("HyperLiquid not configured")
	}

	isBuy := side == "buy"
	action := HLOrderAction{
		Type: "order",
		Order: HLOrder{
			Coin:      coin,
			IsBuy:     isBuy,
			Sz:        sz,
			LimitPx:   "1000000", // high limit price for market orders
			OrderType: "IOC",
			ReduceOnly: false,
		},
		Grouping:   "na",
		BrokerCode: 0,
	}

	// Generate nonce (thread-safe)
	h.nonceMu.Lock()
	h.lastNonce++
	nonce := time.Now().UnixMilli()*1_000_000 + h.lastNonce%1_000_000
	h.nonceMu.Unlock()

	// Sign the action
	sig, err := h.signAction(action, nonce)
	if err != nil {
		return "", fmt.Errorf("sign: %w", err)
	}

	signed := HLSignedAction{
		Action:    action,
		Nonce:     nonce,
		Signature: sig,
	}

	bodyJSON, _ := json.Marshal(signed)

	req, err := http.NewRequest("POST", "https://api.hyperliquid.xyz/exchange", strings.NewReader(string(bodyJSON)))
	if err != nil {
		return "", fmt.Errorf("create request: %w", err)
	}
	req.Header.Set("Content-Type", "application/json")

	resp, err := h.client.Do(req)
	if err != nil {
		return "", fmt.Errorf("http request: %w", err)
	}
	defer resp.Body.Close()

	respBody, _ := io.ReadAll(resp.Body)

	// Parse response
	var response json.RawMessage
	if err := json.Unmarshal(respBody, &response); err != nil {
		return "", fmt.Errorf("parse response: %s", string(respBody))
	}

	// HL returns response as array, e.g. [{"response": {"type": "order", "data": ...}}]
	var results []map[string]json.RawMessage
	if err := json.Unmarshal(respBody, &results); err != nil {
		// Maybe returns single object
		return string(respBody), nil
	}
	if len(results) == 0 {
		return "", fmt.Errorf("empty response: %s", string(respBody))
	}
	respJSON, _ := json.Marshal(results[0])
	return string(respJSON), nil
}

// signAction generates an Ed25519 signature for a HyperLiquid action.
// The signing hash is SHA512(action_json + nonce).
func (h *HyperLiquidTrade) signAction(action HLOrderAction, nonce int64) (string, error) {
	actionJSON, err := json.Marshal(action)
	if err != nil {
		return "", err
	}

	// HL signs: hash = sha512(action_json + nonce)
	nonceBig := big.NewInt(nonce)
	msg := string(actionJSON) + nonceBig.String()
	hash := sha512.Sum512([]byte(msg))

	sig := ed25519.Sign(h.PrivateKey, hash[:])
	return "0x" + hex.EncodeToString(sig), nil
}

// GetHLSize calculates size for a given USD amount on HyperLiquid.
// Uses szDecimals precision from HL's contract universe.
// Returns size as a decimal string complying with HL precision.
// Uses math.Floor to round DOWN to the nearest valid step, consistent with GetBitgetSize.
func GetHLSize(coin string, amountUSD, price float64) string {
	sz := amountUSD / price // raw coin count
	switch coin {
	case "DOGE":
		sz = math.Floor(sz) // step=1, szDecimals=0
		if sz < 1 {
			sz = 1
		}
		return fmt.Sprintf("%.0f", sz)
	case "LINK":
		sz = math.Floor(sz*10) / 10 // step=0.1, szDecimals=1
		if sz < 0.1 {
			sz = 0.1
		}
		return fmt.Sprintf("%.1f", sz)
	case "ONDO":
		sz = math.Floor(sz) // step=1, szDecimals=0
		if sz < 1 {
			sz = 1
		}
		return fmt.Sprintf("%.0f", sz)
	case "OP":
		sz = math.Floor(sz*10) / 10 // step=0.1, szDecimals=1
		if sz < 0.1 {
			sz = 0.1
		}
		return fmt.Sprintf("%.1f", sz)
	case "WIF":
		sz = math.Floor(sz) // step=1, szDecimals=0
		if sz < 1 {
			sz = 1
		}
		return fmt.Sprintf("%.0f", sz)
	case "ARB":
		sz = math.Floor(sz*10) / 10 // step=0.1, szDecimals=1
		if sz < 0.1 {
			sz = 0.1
		}
		return fmt.Sprintf("%.1f", sz)
	default:
		return fmt.Sprintf("%.4f", sz)
	}
}