add util/make_model

src/util/make_model.js

@@ -0,0 +1,183 @@
+/* building a model by postgrest
+ *
+ * a model is simply a cache layer between client
+ * and the database behind an api
+ *
+ * options: {
+ *   endpoint: 'resource location',
+ *   selects: [
+ *     {
+ *       'label': 'column name',
+ *       'alias': 'displayed name',
+ *       'filter': v => value_processor(v)
+ *     }
+ *   ]
+ * }
+ */
+
+export default (options={}) => {
+	// TODO
+	// 1. sigular or prural
+
+	// sanity checks
+	if (typeof options.api == 'undefined' || typeof options.endpoint == 'undefined')
+		throw 'api and endpoint are required options'
+
+	// private model configs
+	let _configs = {
+		// url part
+		api: options.api,
+		endpoint: options.endpoint,
+		endpoint_type: options.endpoint.startsWith('/rpc') ? 'function' : 'relation',
+		// query part
+		selects: options.selects || [],
+	}
+
+	// private model cache & meta-info
+	let _cache = {
+		data: null,
+		count: null
+	}
+
+	// some random places to make things work
+	let _xhr = null
+
+	// construct the model
+	return {
+		// reflection methods
+		configs() { return _configs },
+		cache() { return _cache },
+
+		// main methods
+		select(from=0, to) {
+			// initialize data (singular or plural)
+			_cache.data = _cache.data || []
+
+			// now the hard work
+			return _configs.api.request({
+				method: 'GET',
+				url: _configs.endpoint,
+				headers: _cache.count == null ? {
+					Prefer: 'count=exact'
+				} : {},
+				config: xhr => _xhr = xhr,
+				//
+				// transform model state to postgest queries
+				//queries: [...ambient_queries, ...paging_queries]
+			}).then(response => {
+					// gather begin/end/count
+					let [_range, _count] = _xhr.getResponseHeader('content-range').split('/')
+					let [_begin, _end] = _range.split('-').map(v => ~~v)
+
+					// update count if presented
+					if (_count != '*') _cache.count = _count
+
+					// fill the data cache
+					response.forEach((data, i) => {
+						//					_value_filters.forEach(([label, config]) => data[config.alias || label] = config.value_filter(data[config.alias || label]))
+						_cache.data[_begin + i] = data
+					})
+
+					// for promise
+				return _cache.data.slice(_begin, _end + 1)
+			})
+		}
+	}
+}
+
+export const default1 = (args) => {
+	// private model configs
+	let _configs = {
+		queries: args.queries || [],
+		order: args.order || []
+	}
+	_configs.selects.forEach((config, label, selects) => {
+		selects.set(label, config || {})
+	})
+
+	// prepare the model value filters
+	let _value_filters = Array.from(_configs.selects).filter(([label, config]) => config.value_filter)
+
+	return {
+		// model & model state
+		list: [],
+		count: null,
+		fully_loaded: false,
+		xhr: null,
+
+		// ambient
+		ambient: null,
+		last_ambient: null,
+		ambient_changed() {
+			return this.ambient != this.last_ambient
+		},
+		reset() {
+			// assemble queries for api.request
+			let ambient_queries = [
+				...(_configs.selects ? [{label: 'select', value: Array.from(_configs.selects, ([label, config]) => config.alias ? config.alias + ':' + label : label).join(',')}] : []),
+				...(_configs.queries ? _configs.queries.map(query => ({label: query.label, op: query.op, value: typeof query.value == 'function' ? query.value() : query.value})) : []),
+				...(_configs.order ? [{label: 'order', value: _configs.order.map(o => [o.label, o.direction, o.nulls ? 'nulls'+o.nulls : ''].filter(a => a).join('.')).join(',')}] : [])
+			]
+
+			this.last_ambient = this.ambient
+			this.ambient =JSON.stringify(ambient_queries)
+
+			if (this.ambient_changed()) {
+				this.list = []
+				this.count = null
+				this.fully_loaded = false
+				this.xhr = null
+			}
+
+			return ambient_queries
+		},
+
+		// load data
+		load(args) {
+			args = args || {begin: 0}
+
+			let ambient_queries = this.reset()
+
+			// be lazy: if the data is presented, return the value immediately
+			if (this.list.slice(args.begin, args.end).length == args.limit && this.list.slice(args.begin, args.end).every(data => data != undefined))
+				return Promise.resolve(this.list.slice(args.begin, args.end))
+
+			// create limit&offset for postgrest
+			let paging_queries = []
+			if (args.begin != undefined) {
+				paging_queries.push({label: 'offset', value: args.begin})
+				if (args.end != undefined)
+					paging_queries.push({label: 'limit', value: args.end - args.begin})
+			}
+
+			// now the hard work
+		},
+
+		// load full model if privileged
+		load_full() {
+			this.reset()
+
+			if (this.fully_loaded)
+				return Promise.resolve(this.list)
+
+			return api.request({
+				method: 'POST',
+				url: '/rpc/query_all',
+				body: {
+					endpoint: _configs.endpoint,
+					selects: Array.from(_configs.selects, ([label, config]) => ({label: label, alias: config.alias})),
+					queries: _configs.queries ? _configs.queries.map(query => ({label: query.label, op: query.op, value: typeof query.value == 'function' ? query.value() : query.value})) : [],
+					order: _configs.order
+				}
+			}).then(response => {
+				this.list = response.map(data => {
+					_value_filters.forEach(([label, config]) => data[config.alias || label] = config.value_filter(data[config.alias || label]))
+					return data
+				})
+				this.fully_loaded = true
+
+				return this.list
+			})
+		}
+		}
+	}