queryData.kt

override fun queryClassifyShopsByPrefix(shopCategory: ShopCategory,
                           filterParams: FilterParams): Observable<List<ShopClassifyByPrefix>> {

        return checkIsInit().flatMap { init ->

            Observable
                    // 先把所有東西拿出來
                    .fromCallable {
                        // TODO: 要加一個 Dao 方法： "用 shopCategory 拿所有 ShopEntity"
                        mShopDao.queryAllShop()
                    }
                    // 轉成 Observable<ShopEntity>
                    .flatMapIterable { list -> list }
                    // 做一次 "floor" Filter
                    .filter {

                        if (filterParams.floor == Constant.FILTER_TYPE_ALL) {
                            true
                        } else {
                            it.floor == filterParams.floor
                        }
                    }
                    // 做一次 "type" Filter
                    .filter {

                        if (filterParams.type == Constant.FILTER_TYPE_ALL) {
                            true
                        } else {
                            it.type_en.contains(filterParams.type)
                                    || it.type_tc.contains(filterParams.type)
                                    || it.type_sc.contains(filterParams.type)
                        }
                    }
                    // 用 ShopEntity 的英文名字的第一個字母做 Grouping
                    .groupBy { it.name_en[0].toString() }
                    .flatMap {

                        Timber.d("<DEBUG> group = %s", it.key)

                        var row = 0

                        it
                                // 開始 Observe 接收上一層的 GroupedObservable 的 Observable<ShopEntity>，
                                // 然後把他轉成一個 ShopClassifyByPrefix
                                .reduce(ShopClassifyByPrefix(it.key!!, mutableMapOf())) { model, shop ->

                                    if (!model.shopsByRow.containsKey(row)) {
                                        model.shopsByRow[row] = mutableListOf()
                                    }

                                    model.shopsByRow[row]?.add(shop)

                                    if (model.shopsByRow[row]?.size == 3) {
                                        row++
                                    }

                                    model
                                }
                                .toObservable()
                    }
                    // 接上一層的 ShopClassifyByPrefix 變成 List<ShopClassifyByPrefix>
                    .toList()
                    .toObservable()
        }
    }