package api

import (
    "database/sql"
    "net/http"
    "sort"
)

func MetadataHandler(meta, marketing *sql.DB) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        ds := r.URL.Query().Get("datasource")
        ot := r.URL.Query().Get("order_type")
        db := marketing
        if ds == "ymt" { db = meta }
        tables := []string{}
        if ds == "ymt" {
            tables = []string{"order_info","order_cash","order_voucher","order_digit","goods_voucher_batch","goods_voucher_subject_config","merchant","activity"}
        } else {
            tables = []string{"order","order_detail","order_cash","order_voucher","plan","key_batch","code_batch","voucher","voucher_batch","merchant_key_send"}
        }
        out := []map[string]interface{}{}
        for _, tbl := range tables {
            cols := getColumns(db, tbl)
            fields := []map[string]string{}
            for _, c := range cols {
                tCanonical, fCanonical := canonicalField(ds, tbl, c.Name)
                if tCanonical == "" || fCanonical == "" { continue }
                lab := c.Comment
                if lab == "" { lab = fCanonical }
                fields = append(fields, map[string]string{"key": tCanonical+"."+fCanonical, "field": fCanonical, "label": lab})
            }
            tDisplay := displayTable(ds, tbl)
            out = append(out, map[string]interface{}{"table": tDisplay, "label": tableLabel(tDisplay), "fields": fields})
        }
        sort.Slice(out, func(i, j int) bool { return out[i]["table"].(string) < out[j]["table"].(string) })
        rec := recommendedDefaults(ds, ot)
        ok(w, r, map[string]interface{}{"datasource": ds, "tables": out, "recommended": rec})
    })
}

func tableLabel(t string) string {
    switch t {
    case "order": return "订单主表"
    case "order_detail": return "订单详情"
    case "order_cash": return "红包订单"
    case "order_voucher": return "立减金订单"
    case "order_digit": return "直充卡密订单"
    case "plan": return "活动计划"
    case "key_batch": return "key批次"
    case "code_batch": return "兑换码批次"
    case "voucher": return "立减金"
    case "voucher_batch": return "立减金批次"
    case "merchant_key_send": return "开放平台发放记录"
    case "goods_voucher_batch": return "立减金批次表"
    case "goods_voucher_subject_config": return "立减金主体配置"
    case "merchant": return "客户"
    case "activity": return "活动"
    default: return t
    }
}

func displayTable(ds, tbl string) string {
    if ds == "ymt" && tbl == "order_info" { return "order" }
    return tbl
}

func canonicalField(ds, tbl, col string) (string, string) {
    if ds == "ymt" && tbl == "order_info" {
        switch col {
        case "order_no": return "order", "order_number"
        case "key_code": return "order", "key"
        case "user_id": return "order", "creator"
        case "out_order_no": return "order", "out_trade_no"
        case "activity_id": return "order", "plan_id"
        case "merchant_id": return "order", "reseller_id"
        case "goods_id": return "order", "product_id"
        case "pay_price": return "order", "pay_amount"
        case "key_batch_name": return "order", "key_batch_id"
        default:
            return "order", col
        }
    }
    // other tables: canonical equals actual
    return tbl, col
}

type columnMeta struct{ Name string; Comment string }

func getColumns(db *sql.DB, tbl string) []columnMeta {
    rows, err := db.Query("SELECT COLUMN_NAME, COLUMN_COMMENT FROM information_schema.columns WHERE table_schema = DATABASE() AND table_name = ? ORDER BY ORDINAL_POSITION", tbl)
    if err != nil { return []columnMeta{} }
    defer rows.Close()
    cols := []columnMeta{}
    for rows.Next() {
        var name, comment string
        if err := rows.Scan(&name, &comment); err == nil {
            cols = append(cols, columnMeta{Name: name, Comment: comment})
        }
    }
    return cols
}

func recommendedDefaults(ds, orderType string) []string {
    base := []string{"order.order_number","order.creator","order.out_trade_no","order.type","order.status","order.contract_price","order.num","order.pay_amount","order.create_time"}
    if ds != "ymt" { base = []string{"order.order_number","order.creator","order.out_trade_no","order.type","order.status","order.contract_price","order.num","order.total","order.pay_amount","order.create_time"} }
    t := orderType
    if t == "1" { // 直充卡密
        if ds == "ymt" {
            base = append(base, "order_digit.order_no","order_digit.account","order_digit.success_time")
        } else {
            base = append(base, "plan.title")
        }
    } else if t == "2" { // 立减金
        if ds == "ymt" {
            base = append(base, "order_voucher.channel","order_voucher.status","goods_voucher_batch.channel_batch_no")
        } else {
            base = append(base, "order_voucher.channel","voucher.denomination")
        }
    } else if t == "3" { // 红包
        if ds == "ymt" {
            base = append(base, "order_cash.channel","order_cash.receive_status","order_cash.denomination")
        } else {
            base = append(base, "order_cash.channel","order_cash.receive_status","order_cash.amount")
        }
    }
    return base
}