calldata.go

package main

import (
	"bytes"
	"encoding/binary"
	"fmt"
)

var ETX uint32 = 0x03
var EOT uint32 = 0x04
var ENQ uint32 = 0x05

func main() {
	if h, err := cryptoPrice("BTC", 10); err != nil {
		panic(fmt.Sprintf("%s", err))
	} else {
		fmt.Printf("030000004254430a00000000000000 ==\n%s\n", h)
	}

	if h, err := openWeatherMap("paris", "main", "temp", 1); err != nil {
		panic(fmt.Sprintf("%s", err))
	} else {
		fmt.Printf("050000007061726973040000006d61696e0400000074656d700100000000000000 ==\n%s\n", h)
	}
}

func cryptoPrice(symbol string, multiplier int64) (string, error) {
	// script: 2

	var data = []interface{}{
		uint32(ETX),
		[]byte(symbol),
		uint64(multiplier),
	}

	h, err := buildCalldataHex(data)
	return h, err
}

func openWeatherMap(country string, main_field string, sub_field string, multiplier int64) (string, error) {
	// script: 11

	var data = []interface{}{
		uint32(ENQ),
		[]byte(country),
		uint32(EOT),
		[]byte(main_field),
		uint32(EOT),
		[]byte(sub_field),
		uint64(multiplier),
	}

	h, err := buildCalldataHex(data)
	return h, err
}

func buildCalldataHex(data []interface{}) (string, error) {
	calldata := new(bytes.Buffer)

	for _, v := range data {
		err := binary.Write(calldata, binary.LittleEndian, v)
		if err != nil {
			return "", fmt.Errorf("binary.Write failed:", err)
		}
	}

	return fmt.Sprintf("%x", calldata.Bytes()), nil
}