package tron

import (
  "bytes"
  "encoding/hex"
  "encoding/json"
  "errors"
  "io"
  "math/rand"
  "net/http"
  "os"
  "strings"
  "time"
)

// defaultAPIKeys are the public TronGrid API keys used by tronpy when the
// endpoint is a TronGrid host and no explicit key is supplied.
var defaultAPIKeys = []string{
  "f92221d5-7056-4366-b96f-65d3662ec2d9",
  "1e0a625f-cfa5-43ee-ba41-a09db1aae55f",
  "f399168e-2259-481c-90fc-6b3d984c5463",
  "da63253b-aa9c-46e7-a4e8-22d259a8026d",
  "88c10958-af7b-4d5a-8eef-6e84bf5fb809",
  "169bb4b3-cbe8-449a-984e-80e9adacac55",
}

// HTTPProvider is a minimal JSON-over-HTTP client for a TRON fullnode. It
// mirrors tronpy.providers.HTTPProvider: POST {<method>} with a JSON body and
// an optional Tron-Pro-Api-Key header for TronGrid endpoints.
type HTTPProvider struct {
  endpointURI string
  timeout     time.Duration
  useAPIKey   bool
  apiKeys     []string
  client      *http.Client
}

// NewHTTPProvider creates a provider for the given endpoint URI. When the
// endpoint is a TronGrid host an api key is used (the supplied one, or the
// public defaults). An empty endpoint falls back to the TRONPY_HTTP_PROVIDER_URI
// environment variable and then to api.trongrid.io.
func NewHTTPProvider(endpointURI string, timeout time.Duration, apiKey string) *HTTPProvider {
  if endpointURI == "" {
    endpointURI = os.Getenv("TRONPY_HTTP_PROVIDER_URI")
  }
  if endpointURI == "" {
    endpointURI = "https://api.trongrid.io/"
  }
  p := &HTTPProvider{
    endpointURI: strings.TrimRight(endpointURI, "/"),
    timeout:     timeout,
    client:      &http.Client{Timeout: timeout},
  }
  if strings.Contains(p.endpointURI, "trongrid") {
    p.useAPIKey = true
    if apiKey != "" {
      p.apiKeys = []string{apiKey}
    } else {
      p.apiKeys = append([]string{}, defaultAPIKeys...)
    }
  }
  return p
}

// Endpoint returns the configured endpoint URI.
func (p *HTTPProvider) Endpoint() string { return p.endpointURI }

// makeRequest issues a POST to {endpoint}/{method} with the JSON params.
func (p *HTTPProvider) makeRequest(method string, params any) (map[string]any, error) {
  if params == nil {
    params = map[string]any{}
  }
  body, err := json.Marshal(params)
  if err != nil {
    return nil, err
  }
  for attempt := 0; ; attempt++ {
    req, err := http.NewRequest(http.MethodPost, p.endpointURI+"/"+method, bytes.NewReader(body))
    if err != nil {
      return nil, err
    }
    req.Header.Set("Content-Type", "application/json")
    req.Header.Set("User-Agent", "kisstron")
    if p.useAPIKey && len(p.apiKeys) > 0 {
      req.Header.Set("Tron-Pro-Api-Key", p.apiKeys[rand.Intn(len(p.apiKeys))])
    }
    resp, err := p.client.Do(req)
    if err != nil {
      return nil, err
    }
    data, readErr := io.ReadAll(resp.Body)
    resp.Body.Close()
    if readErr != nil {
      return nil, readErr
    }
    if resp.StatusCode == http.StatusForbidden && strings.Contains(string(data), "Exceed the user daily usage") {
      if !p.rotateAPIKey() || attempt >= len(defaultAPIKeys) {
        return nil, errors.New("rate limit! please add more API keys")
      }
      continue
    }
    if resp.StatusCode < 200 || resp.StatusCode >= 300 {
      return nil, errors.New("http error: " + resp.Status)
    }
    dec := json.NewDecoder(bytes.NewReader(data))
    dec.UseNumber()
    var out map[string]any
    if err := dec.Decode(&out); err != nil {
      return nil, err
    }
    return out, nil
  }
}

func (p *HTTPProvider) rotateAPIKey() bool {
  if len(p.apiKeys) == 0 {
    return false
  }
  p.apiKeys = p.apiKeys[1:]
  return len(p.apiKeys) > 0
}

// handleAPIError maps a node error payload to the same typed errors as
// tronpy. It returns nil when the payload indicates success.
func handleAPIError(payload map[string]any) error {
  if res, ok := payload["result"].(bool); ok && res {
    return nil
  }
  if e, ok := payload["Error"].(string); ok {
    return errors.New(e)
  }
  if code, ok := payload["code"].(string); ok {
    msg := code
    if m, ok := payload["message"].(string); ok {
      if decoded, err := hex.DecodeString(m); err == nil {
        msg = string(decoded)
      } else {
        msg = m
      }
    }
    switch code {
    case "SIGERROR":
      return wrapErr(ErrBadSignature, msg)
    case "TAPOS_ERROR":
      return wrapErr(ErrTapos, msg)
    case "TRANSACTION_EXPIRATION_ERROR", "TOO_BIG_TRANSACTION_ERROR":
      return wrapErr(ErrTransaction, msg)
    case "CONTRACT_VALIDATE_ERROR":
      return wrapErr(ErrValidation, msg)
    default:
      return wrapErr(ErrAPI, msg)
    }
  }
  if res, ok := payload["result"].(map[string]any); ok {
    return handleAPIError(res)
  }
  return nil
}