From d8017615c75ec62be48d09fa53bbb58e93656c9c Mon Sep 17 00:00:00 2001
From: Kim Alvefur <zash@zash.se>
Date: Wed, 29 Dec 2021 16:52:09 +0100
Subject: util.jsonpointer: Resolve JSON Pointers per RFC 6901

---
 util/jsonpointer.lua | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)
 create mode 100644 util/jsonpointer.lua

(limited to 'util')

diff --git a/util/jsonpointer.lua b/util/jsonpointer.lua
new file mode 100644
index 00000000..7c657266
--- /dev/null
+++ b/util/jsonpointer.lua
@@ -0,0 +1,40 @@
+local function unescape_token(escaped_token)
+	local unescaped = escaped_token:gsub("~1", "/"):gsub("~0", "~")
+	return unescaped
+end
+
+local function resolve_json_pointer(ref, path)
+	local ptr_len = #path + 1
+	for part, pos in path:gmatch("/([^/]*)()") do
+		local token = unescape_token(part)
+		if not (type(ref) == "table") then
+			return nil
+		end
+		local idx = next(ref)
+		local new_ref
+
+		if type(idx) == "string" then
+			new_ref = ref[token]
+		elseif math.type(idx) == "integer" then
+			local i = tonumber(token)
+			if token == "-" then
+				i = #ref + 1
+			end
+			new_ref = ref[i]
+		else
+			return nil, "invalid-table"
+		end
+
+		if pos == ptr_len then
+			return new_ref
+		elseif type(new_ref) == "table" then
+			ref = new_ref
+		elseif not (type(ref) == "table") then
+			return nil, "invalid-path"
+		end
+
+	end
+	return ref
+end
+
+return { resolve = resolve_json_pointer }
-- 
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