package exporter

import (
    "encoding/json"
    "errors"
    "strings"
)

type BuildRequest struct {
    MainTable string
    Fields []string
    Filters map[string]interface{}
}

func BuildSQL(req BuildRequest, whitelist map[string]bool) (string, []interface{}, error) {
    if req.MainTable != "order" {
        return "", nil, errors.New("unsupported main table")
    }
    cols := []string{}
    for _, f := range req.Fields {
        if !whitelist["order."+f] {
            return "", nil, errors.New("field not allowed")
        }
        if f == "key" || req.MainTable == "order" {
            cols = append(cols, "`order`."+escape(f))
        }
    }
    if len(cols) == 0 {
        return "", nil, errors.New("no fields")
    }
    sb := strings.Builder{}
    sb.WriteString("SELECT ")
    sb.WriteString(strings.Join(cols, ","))
    sb.WriteString(" FROM `order`")
    args := []interface{}{}
    where := []string{}
    if v, ok := req.Filters["creator_in"]; ok {
        ids := []interface{}{}
        switch t := v.(type) {
        case []interface{}:
            ids = t
        case []int:
            for _, x := range t {
                ids = append(ids, x)
            }
        case []string:
            for _, x := range t {
                ids = append(ids, x)
            }
        }
        if len(ids) == 0 {
            return "", nil, errors.New("creator_in required")
        }
        ph := strings.Repeat("?,", len(ids))
        ph = strings.TrimSuffix(ph, ",")
        where = append(where, "`order`.creator IN ("+ph+")")
        args = append(args, ids...)
    } else {
        return "", nil, errors.New("creator_in required")
    }
    if v, ok := req.Filters["create_time_between"]; ok {
        var arr []interface{}
        b, _ := json.Marshal(v)
        json.Unmarshal(b, &arr)
        if len(arr) != 2 {
            return "", nil, errors.New("create_time_between requires 2 values")
        }
        where = append(where, "`order`.create_time BETWEEN ? AND ?")
        args = append(args, arr[0], arr[1])
    }
    if len(where) > 0 {
        sb.WriteString(" WHERE ")
        sb.WriteString(strings.Join(where, " AND "))
    }
    return sb.String(), args, nil
}

func escape(s string) string {
    if s == "key" {
        return "`key`"
    }
    return s
}