package tron

import (
  "encoding/hex"
  "encoding/json"
  "errors"
  "time"
)

// Transaction is a signed or unsigned TRON transaction. Its field order matches
// tronpy's Transaction.to_json() dict order so the marshalled JSON is
// byte-compatible with the Python offline output.
type Transaction struct {
  TxID       string   `json:"txID"`
  RawData    *RawData `json:"raw_data"`
  Signature  []string `json:"signature"`
  Permission any      `json:"permission"`
  client     *Client
}

func currentMillis() int64 {
  return time.Now().UnixNano() / int64(time.Millisecond)
}

// TransactionBuilder assembles a transaction before signing.
type TransactionBuilder struct {
  client  *Client
  rawData *RawData
}

// newTransactionBuilder creates a builder for a single contract.
func (c *Client) newTransactionBuilder(typ string, value any) *TransactionBuilder {
  now := currentMillis()
  rd := &RawData{
    Contract: []ContractJSON{{
      Parameter: ParameterJSON{
        Value:   value,
        TypeURL: "type.googleapis.com/protocol." + typ,
      },
      Type: typ,
    }},
    Timestamp:  now,
    Expiration: now + 60000,
  }
  if typ == "TriggerSmartContract" || typ == "CreateSmartContract" {
    rd.FeeLimit = c.feeLimit
  }
  return &TransactionBuilder{client: c, rawData: rd}
}

// Transfer builds a TRX transfer builder. Amount is in SUN.
func (c *Client) Transfer(from, to string, amount int64) (*TransactionBuilder, error) {
  fromHex, err := ToHexAddress(from)
  if err != nil {
    return nil, err
  }
  toHex, err := ToHexAddress(to)
  if err != nil {
    return nil, err
  }
  return c.newTransactionBuilder("TransferContract", TransferValue{
    OwnerAddress: fromHex,
    ToAddress:    toHex,
    Amount:       amount,
  }), nil
}

// FreezeBalance builds a FreezeBalanceV2 builder for the given resource.
func (c *Client) FreezeBalance(owner string, amount int64, resource string) (*TransactionBuilder, error) {
  ownerHex, err := ToHexAddress(owner)
  if err != nil {
    return nil, err
  }
  return c.newTransactionBuilder("FreezeBalanceV2Contract", FreezeValue{
    OwnerAddress:  ownerHex,
    FrozenBalance: amount,
    Resource:      resource,
  }), nil
}

// UnfreezeBalance builds an UnfreezeBalanceV2 builder for the given resource.
func (c *Client) UnfreezeBalance(owner string, amount int64, resource string) (*TransactionBuilder, error) {
  ownerHex, err := ToHexAddress(owner)
  if err != nil {
    return nil, err
  }
  return c.newTransactionBuilder("UnfreezeBalanceV2Contract", UnfreezeValue{
    OwnerAddress:    ownerHex,
    UnfreezeBalance: amount,
    Resource:        resource,
  }), nil
}

// Build fills the reference block fields from the chain and computes the txid.
func (b *TransactionBuilder) Build() (*Transaction, error) {
  refID, err := b.client.getLatestSolidBlockID()
  if err != nil {
    return nil, err
  }
  if len(refID) < 32 {
    return nil, ErrBadHash
  }
  b.rawData.RefBlockBytes = refID[12:16]
  b.rawData.RefBlockHash = refID[16:32]
  txid, err := b.rawData.TxID()
  if err != nil {
    return nil, err
  }
  return &Transaction{
    TxID:      txid,
    RawData:   b.rawData,
    Signature: []string{},
    client:    b.client,
  }, nil
}

// Sign signs the transaction with the given private key.
func (tx *Transaction) Sign(key *PrivateKey) error {
  if tx.TxID == "" {
    return ErrTransaction
  }
  hash, err := hex.DecodeString(tx.TxID)
  if err != nil {
    return err
  }
  sig, err := key.Sign(hash)
  if err != nil {
    return err
  }
  tx.Signature = append(tx.Signature, hex.EncodeToString(sig))
  return nil
}

// Broadcast sends the signed transaction and returns the raw response.
func (tx *Transaction) Broadcast() (map[string]any, error) {
  if tx.client == nil {
    return nil, ErrTransaction
  }
  return tx.client.broadcast(tx)
}

// Wait polls for the transaction receipt, matching TransactionRet.wait().
func (tx *Transaction) Wait(timeout, interval time.Duration) (map[string]any, error) {
  if tx.client == nil {
    return nil, ErrTransaction
  }
  deadline := time.Now().Add(timeout)
  for time.Now().Before(deadline) {
    info, err := tx.client.getTransactionInfo(tx.TxID)
    if err == nil {
      return info, nil
    }
    if !errors.Is(err, ErrTransactionNotFound) {
      return nil, err
    }
    time.Sleep(interval)
  }
  return nil, ErrTransactionNotFound
}

// JSON returns the compact transaction JSON used for node requests and offline
// mode output, matching json.dumps(txn.to_json(), separators=(",", ":")).
func (tx *Transaction) JSON() string {
  b, _ := json.Marshal(tx)
  return string(b)
}

// toJSON returns the transaction as a generic map for node requests.
func (tx *Transaction) toJSON() map[string]any {
  var m map[string]any
  json.Unmarshal([]byte(tx.JSON()), &m)
  return m
}

// TransactionFromJSON parses a transaction previously exported by JSON().
func TransactionFromJSON(s string) (*Transaction, error) {
  var decoded struct {
    TxID       string   `json:"txID"`
    RawData    *RawData `json:"raw_data"`
    Signature  []string `json:"signature"`
    Permission any      `json:"permission"`
  }
  if err := json.Unmarshal([]byte(s), &decoded); err != nil {
    return nil, err
  }
  if decoded.RawData == nil {
    return nil, ErrTransaction
  }
  return &Transaction{
    TxID:       decoded.TxID,
    RawData:    decoded.RawData,
    Signature:  decoded.Signature,
    Permission: decoded.Permission,
  }, nil
}

// ParseTransaction parses exported transaction JSON and attaches the client so
// the transaction can be broadcast (mirrors Transaction.from_json + _client).
func (c *Client) ParseTransaction(raw string) (*Transaction, error) {
  tx, err := TransactionFromJSON(raw)
  if err != nil {
    return nil, err
  }
  tx.client = c
  return tx, nil
}