casey-chow/tigertrade

package models

import (
    "database/sql"
    "errors"
    sq "github.com/Masterminds/squirrel"
    log "github.com/Sirupsen/logrus"
    "net/http"
    "time"
)

// PostgreSQL Statement Builder instance
var psql = sq.StatementBuilder.PlaceholderFormat(sq.Dollar)

// Default and maximum number of datum returned by bulk API queries
// Used when obtaining and displaying many datum of a given structure
const defaultNumResults uint64 = 30

type emptyQuery struct{}

func (_ emptyQuery) ToSql() (string, []interface{}, error) {
    return "", nil, nil
}

// getExecResultCode is a standard way to extract an HTTP error out of an SQL result
func getExecResultCode(result sql.Result, err error) (int, error) {
    if err != nil {
        return http.StatusInternalServerError, err
    }
    numRows, err := result.RowsAffected()
    if err != nil {
        return http.StatusInternalServerError, err
    }
    if numRows == 0 {
        return http.StatusNotFound, sql.ErrNoRows
    }
    if numRows != 1 {
        return http.StatusInternalServerError, errors.New("multiple rows affected")
    }
    return http.StatusNoContent, nil
}

// getExecDoNothingResultCode is like getExecResultCode,
// but should be used when the SQL operation affecting no rows is not an error
func getExecDoNothingResultCode(result sql.Result, err error) (int, error) {
    code, err := getExecResultCode(result, err)
    if code == http.StatusNotFound {
        return http.StatusNoContent, nil
    }
    return code, err
}

// https://coderwall.com/p/cp5fya/measuring-execution-time-in-go
func logTime(start time.Time, name string) {
    elapsed := time.Since(start)
    log.WithField("took", elapsed).
        Infof("completed execution of %s", name)
}

// https://goo.gl/BPVkA6
func stringUnique(s []string) []string {
    seen := make(map[string]struct{}, len(s))
    j := 0
    for _, v := range s {
        if _, ok := seen[v]; ok {
            continue
        }
        seen[v] = struct{}{}
        s[j] = v
        j++
    }
    return s[:j]
}