From 2534946eada21c06dd155c08e8aa44719a914274 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?R=C3=A9mi?= <33205215+remimimimi@users.noreply.github.com>
Date: Sun, 19 Sep 2021 18:36:26 +0000
Subject: [PATCH] json: support sumtypes (#11549)

---
 vlib/json/json_test.v | 42 +++++++++++++++++++++++++++++++
 vlib/v/gen/c/json.v   | 57 +++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 97 insertions(+), 2 deletions(-)

diff --git a/vlib/json/json_test.v b/vlib/json/json_test.v
index 1c9f5b4496..53323ba3d1 100644
--- a/vlib/json/json_test.v
+++ b/vlib/json/json_test.v
@@ -37,6 +37,48 @@ fn test_decode_top_level_array() {
 	assert x[1].age == 31
 }
 
+struct Usr {
+	name string
+}
+
+struct Item {
+	tag string
+}
+
+enum Animal {
+	dog // Will be encoded as `0`
+	cat
+}
+
+type Entity = Animal | Item | Usr | string | time.Time
+
+struct SomeGame {
+	title  string
+	player Entity
+	other  []Entity
+}
+
+fn test_encode_decode_sumtype() ? {
+	game := SomeGame{
+		title: 'Super Mega Game'
+		player: Usr{'PoopLord69'}
+		other: [
+			Entity(Item{'Pen'}),
+			Item{'Cookie'},
+			Animal.dog,
+			'Stool',
+			time.now(),
+		]
+	}
+
+	enc := json.encode(game)
+	dec := json.decode(SomeGame, enc) ?
+
+	assert game.title == dec.title
+	assert game.player == dec.player
+	assert (game.other[4] as time.Time).unix_time() == (dec.other[4] as time.Time).unix_time()
+}
+
 fn bar<T>(payload string) ?Bar { // ?T doesn't work currently
 	result := json.decode(T, payload) ?
 	return result
diff --git a/vlib/v/gen/c/json.v b/vlib/v/gen/c/json.v
index 5a45420517..fb5e4a1d06 100644
--- a/vlib/v/gen/c/json.v
+++ b/vlib/v/gen/c/json.v
@@ -24,6 +24,7 @@ fn (mut g Gen) gen_json_for_type(typ ast.Type) {
 	mut enc := strings.new_builder(100)
 	sym := g.table.get_type_symbol(utyp)
 	styp := g.typ(utyp)
+	g.register_optional(utyp)
 	if is_js_prim(sym.name) || sym.kind == .enum_ {
 		return
 	}
@@ -39,8 +40,6 @@ fn (mut g Gen) gen_json_for_type(typ ast.Type) {
 	// cJSON_Parse(str) call is added by the compiler
 	// Code gen decoder
 	dec_fn_name := js_dec_name(styp)
-	// Make sure that this optional type actually exists
-	g.register_optional(utyp)
 	dec_fn_dec := 'Option_$styp ${dec_fn_name}(cJSON* root)'
 	dec.writeln('
 $dec_fn_dec {
@@ -91,6 +90,13 @@ $enc_fn_dec {
 			verror('json: $sym.name is not struct')
 		}
 		g.gen_struct_enc_dec(psym.info, styp, mut enc, mut dec)
+	} else if sym.kind == .sum_type {
+		enc.writeln('\to = cJSON_CreateObject();')
+		// Structs. Range through fields
+		if sym.info !is ast.SumType {
+			verror('json: $sym.name is not a sumtype')
+		}
+		g.gen_sumtype_enc_dec(sym, mut enc, mut dec)
 	} else {
 		enc.writeln('\to = cJSON_CreateObject();')
 		// Structs. Range through fields
@@ -109,6 +115,53 @@ $enc_fn_dec {
 	g.gowrappers.writeln(enc.str())
 }
 
+[inline]
+fn (mut g Gen) gen_sumtype_enc_dec(sym ast.TypeSymbol, mut enc strings.Builder, mut dec strings.Builder) {
+	info := sym.info as ast.SumType
+	typ := sym.idx
+
+	for variant in info.variants {
+		variant_typ := g.typ(variant)
+		variant_sym := g.table.get_type_symbol(variant)
+
+		g.gen_json_for_type(variant)
+		g.write_sumtype_casting_fn(variant, typ)
+		g.definitions.writeln('static inline $sym.cname ${variant_typ}_to_sumtype_${sym.cname}($variant_typ* x);')
+
+		// ENCODING
+		enc.writeln('\tif (val._typ == $variant) {')
+		if variant_sym.kind == .enum_ {
+			enc.writeln('\t\tcJSON_AddItemToObject(o, "$variant_sym.name", json__encode_u64(*val._$variant_typ));')
+		} else if variant_sym.name == 'time.Time' {
+			enc.writeln('\t\tcJSON_AddItemToObject(o, "$variant_sym.name", json__encode_i64(val._$variant_typ->_v_unix));')
+		} else {
+			enc.writeln('\t\tcJSON_AddItemToObject(o, "$variant_sym.name", json__encode_${variant_typ}(*val._$variant_typ));')
+		}
+		enc.writeln('\t}')
+
+		// DECODING
+		dec.writeln('\tif (strcmp("$variant_sym.name", root->child->string) == 0) {')
+		tmp := g.new_tmp_var()
+		if is_js_prim(variant_typ) {
+			gen_js_get(variant_typ, tmp, variant_sym.name, mut dec, false)
+			dec.writeln('\t\t$variant_typ value = (${js_dec_name(variant_sym.name)})(jsonroot_$tmp);')
+		} else if variant_sym.kind == .enum_ {
+			gen_js_get(variant_typ, tmp, variant_sym.name, mut dec, false)
+			dec.writeln('\t\t$variant_typ value = json__decode_u64(jsonroot_$tmp);')
+		} else if variant_sym.name == 'time.Time' {
+			gen_js_get(variant_typ, tmp, variant_sym.name, mut dec, false)
+			dec.writeln('\t\t$variant_typ value = time__unix(json__decode_i64(jsonroot_$tmp));')
+		} else {
+			gen_js_get_opt(js_dec_name(variant_sym.cname), variant_typ, sym.cname, tmp,
+				variant_sym.name, mut dec, false)
+			// dec.writeln('\t\tOption_${variant_typ} $tmp = json__decode_${variant_typ}(js_get(root, "$variant_sym.name"));')
+			dec.writeln('\t\t$variant_typ value = *($variant_typ*)(${tmp}.data);')
+		}
+		dec.writeln('\t\tres = ${variant_typ}_to_sumtype_${sym.cname}(&value);')
+		dec.writeln('\t}')
+	}
+}
+
 [inline]
 fn (mut g Gen) gen_struct_enc_dec(type_info ast.TypeInfo, styp string, mut enc strings.Builder, mut dec strings.Builder) {
 	info := type_info as ast.Struct