evolution.go

package main

import (
	"bytes"
	"context"
	"encoding/csv"
	"fmt"
	"log"
	"net/http"
	"strconv"
	"time"

	"github.com/jackc/pgx/v4/pgxpool"
	"github.com/labstack/echo/v4"
)

type DolarEvolutionDay struct {
	Date      string `json:"date"`
	Source    string `json:"source"`
	ValueSell Number `json:"value_sell"`
	ValueBuy  Number `json:"value_buy"`
}

func getDolarEvolutionData(days string, db *pgxpool.Pool) []DolarEvolutionDay {
	limitStr := ""
	var res []DolarEvolutionDay
	if days != "" {
		days_num, err := strconv.Atoi(days)
		if err == nil && days_num < 10000 {
			limitStr = "limit " + days
		}
	}

	rows, err := db.Query(context.Background(), `
	select
		dttm, tipo, value_sell, value_buy
	from
		dolar_evolution
	order by
		dttm desc
	`+limitStr)
	if err != nil {
		log.Fatal(err)
	}
	defer rows.Close()

	for rows.Next() {
		var objAppend DolarEvolutionDay
		var dateObj time.Time

		if err := rows.Scan(&dateObj, &objAppend.Source, &objAppend.ValueSell, &objAppend.ValueBuy); err != nil {
			log.Fatal(err)
		}
		objAppend.Date = fmt.Sprintf(dateObj.Format("2006-01-02"))

		res = append(res, objAppend)
	}

	return res
}

func dolar_evolution_json(c echo.Context, db *pgxpool.Pool) error {
	days := c.QueryParam("days")
	res_data := getDolarEvolutionData(days, db)

	return c.JSON(http.StatusOK, res_data)
}

func dolar_evolution_csv(c echo.Context, db *pgxpool.Pool) error {
	days := c.QueryParam("days")
	res_data := getDolarEvolutionData(days, db)

	csv_data := [][]string{
		{"day", "type", "value_buy", "value_sell"},
	}

	for _, d := range res_data {
		tmp := []string{d.Date, d.Source, fmt.Sprintf("%.2f", d.ValueBuy), fmt.Sprintf("%.2f", d.ValueSell)}
		csv_data = append(csv_data, tmp)
	}

	b := new(bytes.Buffer)
	w := csv.NewWriter(b)

	w.WriteAll(csv_data)

	if err := w.Error(); err != nil {
		log.Fatal(err)
	}

	return c.Blob(http.StatusOK, "text/csv", b.Bytes())
}