init match & replace plugin

Signed-off-by: Hadi <112569860+anotherhadi@users.noreply.github.com>

plugins/match_replace.lua

@@ -0,0 +1,125 @@
+Plugin = {
+	name = "Match & Replace",
+	description = [[
+Automatically find and replace content in requests and responses.
+
+**Config** (YAML):
+```yaml
+rules:
+  - on: "request"         # "request", "response", or "both" (default: "both")
+    url: "example%.com"   # optional: Lua pattern to filter by URL
+    target: "body"        # "body", "path", "url", or "header:Name"
+    find: "old_string"    # Lua pattern to search
+    replace: "new_string" # replacement string (supports %1, %2 for captures)
+```
+
+Example (inject a debug flag in JSON bodies):
+```yaml
+rules:
+  - on: "both"
+    url: "api%.example%.com"
+    target: "body"
+    find: '"debug":false'
+    replace: '"debug":true'
+```
+
+Example (replace an Authorization header):
+```yaml
+rules:
+  - on: "request"
+    target: "header:Authorization"
+    find: "Bearer .*"
+    replace: "Bearer MY_NEW_TOKEN"
+```
+
+Example (rewrite a path prefix):
+```yaml
+rules:
+  - on: "request"
+    url: "staging%.example%.com"
+    target: "path"
+    find: "^/v1/"
+    replace: "/v2/"
+```
+  ]],
+	priority = 50,
+	on_request = { sync = true },
+	on_response = { sync = true },
+}
+
+local rules = {}
+
+function on_config()
+	rules = {}
+	local cfg = get_config()
+	if not cfg or not cfg.rules then
+		return
+	end
+	for _, r in ipairs(cfg.rules) do
+		if r.find and r.find ~= "" then
+			table.insert(rules, {
+				on = r.on or "both",
+				url = r.url,
+				target = r.target or "body",
+				find = r.find,
+				replace = r.replace or "",
+			})
+		end
+	end
+end
+
+local function should_apply(rule, req, context)
+	if rule.on ~= "both" and rule.on ~= context then
+		return false
+	end
+	if rule.url and not req.url:match(rule.url) then
+		return false
+	end
+	return true
+end
+
+local function apply(rule, req, res, context)
+	local target = rule.target
+	if target == "body" then
+		local obj = (context == "response") and res or req
+		local body = obj:get_body()
+		local new_body = body:gsub(rule.find, rule.replace)
+		if new_body ~= body then
+			obj:set_body(new_body)
+		end
+	elseif target == "path" then
+		local new_path = req.path:gsub(rule.find, rule.replace)
+		if new_path ~= req.path then
+			req:set_path(new_path)
+		end
+	elseif target == "url" then
+		local new_url = req.url:gsub(rule.find, rule.replace)
+		if new_url ~= req.url then
+			req:set_url(new_url)
+		end
+	elseif target:sub(1, 7) == "header:" then
+		local name = target:sub(8)
+		local obj = (context == "response") and res or req
+		local val = obj.headers[name] or ""
+		local new_val = val:gsub(rule.find, rule.replace)
+		if new_val ~= val then
+			obj:set_header(name, new_val)
+		end
+	end
+end
+
+function on_request(req)
+	for _, rule in ipairs(rules) do
+		if should_apply(rule, req, "request") then
+			apply(rule, req, nil, "request")
+		end
+	end
+end
+
+function on_response(req, res)
+	for _, rule in ipairs(rules) do
+		if should_apply(rule, req, "response") then
+			apply(rule, req, res, "response")
+		end
+	end
+end