From ef4e0b1a15d58814518117d096c5d9e4b0102cba Mon Sep 17 00:00:00 2001
From: Bing Sun <subi.the.dream.walker@gmail.com>
Date: Tue, 12 May 2020 22:22:57 +0800
Subject: [PATCH] make_model: polish the state & cache handling

---
 src/util/make_model.js | 57 +++++++++++++++++++++++++-----------------
 1 file changed, 34 insertions(+), 23 deletions(-)

diff --git a/src/util/make_model.js b/src/util/make_model.js
index eb20761..fd122b0 100644
--- a/src/util/make_model.js
+++ b/src/util/make_model.js
@@ -37,18 +37,18 @@ export default (options={}) => {
 
 	// private model cache & meta-info
 	let _cache = {
-		// upstream (data) cache
+		// upstream data cache
 		data: null,
 		count: null,
-		upstream_limit: null,
-
-		// local cache
-		ambient: null,
-		last_ambient: null,
+		upstream_limit: null
 	}
 
-	// some random variables to make things work
+	// model state
 	let _state = {
+		// model ambient that determines the data content
+		ambient: null,
+		last_ambient: null,
+		// async states
 		xhr: null,
 		promise: null,
 		loading: false
@@ -61,24 +61,29 @@ export default (options={}) => {
 		cache() { return _cache },
 		data(offset=0, limit=Infinity) { return _cache.data && _cache.data.slice(offset, offset+limit) || [] },
 		ambient_changed() {
-			return _cache.ambient != _cache.last_ambient
+			return _state.ambient != _state.last_ambient
 		},
-		reset() {
-			let ambient_queries = [
+
+		// clean state and cache if necessary
+		clean() {
+			// always clean async state
+			_state.xhr = null
+			_state.promise = null
+			_state.loading = false
+
+			// update ambient state
+			_state.last_ambient = _state.ambient
+			_state.ambient =JSON.stringify([
 				...(_configs.selects ? _configs.selects : []),
 				...(_configs.wheres ? _configs.wheres.map(where => ({label: where.label, op: where.op, value: typeof where.value == 'function' ? where.value() : where.value})) : []),
 				...(_configs.order ? _configs.order : [])
-			]
-
-			_cache.last_ambient = _cache.ambient
-			_cache.ambient =JSON.stringify(ambient_queries)
+			])
 
+			// clean cache if ambient changes
 			if (this.ambient_changed()) {
 				_cache.data = []
 				_cache.count = null
 				_cache.upstream_limit = null
-				_state.xhr = null
-				//this.fully_loaded = false
 			}
 		},
 
@@ -94,8 +99,14 @@ export default (options={}) => {
 
 			// be lazy 2: if there is a promise, return it if ambient matches or
 			// cancel it
-			if (_state.promise != null)
-				return _state.promise
+			if (_state.promise != null) {
+				if (this.ambient_changed()) {
+					if (_state.xhr != null) _state.xhr.abort()
+					_state.xhr = null
+				}
+				else
+					return _state.promise
+			}
 
 			// TODO
 			// ambient = select + order + limit/offset
@@ -164,12 +175,10 @@ export default (options={}) => {
 				if (_end - _begin + 1 < limit)
 					console.warn('The response range is narrower than requested, probably due to an upstream hard limit.')
 
-				// clean model state
-				_state.promise = null
-				this.reset()
-
 				// return data
 				return _cache.data.slice(_begin, _end + 1)
+			}).finally(() => {
+				this.clean()
 			})
 
 			return _state.promise
@@ -208,6 +217,8 @@ export default (options={}) => {
 				// clean state
 				_state.promise = null
 				this.reset()
+			}).finally(() => {
+				this.clean()
 			})
 
 			return _state.promise
@@ -271,6 +282,6 @@ export default (options={}) => {
 	}
 
 	// initialize model
-	_model.reset()
+	_model.clean()
 	return _model
 }