Julien Riou
da532104f8
To avoid scalpers' price, the bot now understand filters on prices
using a minimum and maximum value, in a currency and a pattern to
detect the model.
Example:
```
"price_ranges": [
{"model": "3090", "max": 3000, "currency": "EUR"},
{"model": "3080", "max": 1600, "currency": "EUR"},
{"model": "3070", "max": 1200, "currency": "EUR"}
],
```
More details in README.md.
Signed-off-by: Julien Riou <julien@riou.xyz>
96 lines
2.8 KiB
Go
96 lines
2.8 KiB
Go
package main
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import (
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"encoding/json"
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"fmt"
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"io/ioutil"
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"net/http"
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"strings"
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log "github.com/sirupsen/logrus"
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)
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// CurrencyConverter to cache rates of different currency pairs
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type CurrencyConverter struct {
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rates map[string]float64
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}
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// NewCurrencyConverter to create a CurrencyConverter
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func NewCurrencyConverter() *CurrencyConverter {
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return &CurrencyConverter{
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rates: make(map[string]float64),
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}
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}
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// Convert an amount in a given currency to another currency
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// Eventually fetch rate from a remote API then cache the result
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func (c *CurrencyConverter) Convert(amount float64, fromCurrency string, toCurrency string) (float64, error) {
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var err error
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if fromCurrency == toCurrency {
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return amount, nil
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}
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// exclude invalid currencies
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if fromCurrency == "" || toCurrency == "" {
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return 0.0, fmt.Errorf("invalid currency pair used for convertion (from='%s', to='%s')", fromCurrency, toCurrency)
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}
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// searching currency pair rate in cache
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pair := fmt.Sprintf("%s%s", strings.ToLower(fromCurrency), strings.ToLower(toCurrency))
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rate, exists := c.rates[pair]
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if !exists {
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// fetching rate from api
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rate, err = c.getRate(fromCurrency, toCurrency)
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if err != nil {
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return 0.0, err
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}
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// store rate in cache
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c.rates[pair] = rate
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}
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return rate * amount, nil
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}
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// CurrencyResponse to unmarshall JSON response from API
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type CurrencyResponse struct {
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Date string `json:"date"`
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Rate float64 `json:"rate"`
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}
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// getRate retreives rate from a remote API
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func (c *CurrencyConverter) getRate(fromCurrency string, toCurrency string) (float64, error) {
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if fromCurrency == "" || toCurrency == "" {
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return 0.0, fmt.Errorf("invalid currency pair used for convertion (from=%s, to=%s)", fromCurrency, toCurrency)
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}
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// lowering currency names to match the API route
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fromCurrency = strings.ToLower(fromCurrency)
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toCurrency = strings.ToLower(toCurrency)
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log.Debugf("fetching %s%s rate from currency api", fromCurrency, toCurrency)
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resp, err := http.Get("https://cdn.jsdelivr.net/gh/fawazahmed0/currency-api@1/latest/currencies/" + fromCurrency + "/" + toCurrency + ".json")
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if err != nil {
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return 0.0, fmt.Errorf("could not retreive currency rates for pair %s%s: %s", fromCurrency, toCurrency, err)
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}
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defer resp.Body.Close()
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body, err := ioutil.ReadAll(resp.Body)
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if err != nil {
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return 0.0, fmt.Errorf("could not parse currency rates response for pair %s%s: %s", fromCurrency, toCurrency, err)
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}
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// response has a dynamic name for the rate
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// -> {"date": "2021-05-22", "usd": 1.218125}
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// making it predictable
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// -> {"date": "2021-05-22", "rate": 1.218125}}
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bodyParsed := strings.Replace(string(body), toCurrency, "rate", 1)
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var response CurrencyResponse
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err = json.Unmarshal([]byte(bodyParsed), &response)
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if err != nil {
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return 0.0, err
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}
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return response.Rate, nil
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}
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