package exporter

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

type BuildRequest struct {
    MainTable string
    Fields []string // table.field
    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{}
    need := map[string]bool{}
    for _, tf := range req.Fields {
        if !whitelist[tf] {
            return "", nil, errors.New("field not allowed")
        }
        parts := strings.Split(tf, ".")
        if len(parts) != 2 { return "", nil, errors.New("invalid field format") }
        t, f := parts[0], parts[1]
        need[t] = true
        if t == "order" {
            cols = append(cols, "`order`."+escape(f))
        } else {
            cols = append(cols, "`"+t+"`."+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`")
    // JOINs based on need
    // order_detail
    if need["order_detail"] { sb.WriteString(" LEFT JOIN `order_detail` ON `order_detail`.order_number = `order`.order_number") }
    // order_cash
    if need["order_cash"] { sb.WriteString(" LEFT JOIN `order_cash` ON `order_cash`.order_number = `order`.order_number") }
    // order_voucher
    if need["order_voucher"] { sb.WriteString(" LEFT JOIN `order_voucher` ON `order_voucher`.order_number = `order`.order_number") }
    // plan
    if need["plan"] || need["key_batch"] { sb.WriteString(" LEFT JOIN `plan` ON `plan`.id = `order`.plan_id") }
    // key_batch depends on plan
    if need["key_batch"] { sb.WriteString(" LEFT JOIN `key_batch` ON `key_batch`.plan_id = `plan`.id") }
    // code_batch depends on key_batch
    if need["code_batch"] { sb.WriteString(" LEFT JOIN `code_batch` ON `code_batch`.key_batch_id = `key_batch`.id") }
    // voucher depends on order_voucher
    if need["voucher"] { sb.WriteString(" LEFT JOIN `voucher` ON `voucher`.channel_activity_id = `order_voucher`.channel_activity_id") }
    // voucher_batch depends on voucher
    if need["voucher_batch"] { sb.WriteString(" LEFT JOIN `voucher_batch` ON `voucher_batch`.voucher_id = `voucher`.id") }
    // merchant_key_send depends on order.key
    if need["merchant_key_send"] { sb.WriteString(" LEFT JOIN `merchant_key_send` ON `order`." + escape("key") + " = `merchant_key_send`.key") }

    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...)
    }
    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 v, ok := req.Filters["type_eq"]; ok {
        var tv int
        switch t := v.(type) {
        case float64:
            tv = int(t)
        case int:
            tv = t
        case string:
            // simple digits parsing
            for i := 0; i < len(t); i++ { c := t[i]; if c<'0'||c>'9' { continue }; tv = tv*10 + int(c-'0') }
        }
        if tv == 1 || tv == 2 || tv == 3 {
            where = append(where, "`order`.type = ?")
            args = append(args, tv)
        }
    }
    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
}