aider: Add public API to add a RequestModification to fire only once.

# Aider chat conversation:

USER: Modify proxychain.go such that there is a public API to add a RequestModification to fire only once.

ASSISTANT: To make this change we need to modify `proxychain/proxychain.go` to:

1. Add a new field `onceRequestModifications` in the `ProxyChain` struct to store the request modifications that should only fire once.
2. Add a new method `AddOnceRequestModification` to add a request modification that should only fire once.
3. Update the `_execute` method to apply the `onceRequestModifications` and clear them after they have been applied.

Here are the *SEARCH/REPLACE* blocks:

proxychain/proxychain.go
<source>
<<<<<<< SEARCH
type ProxyChain struct {
	Context              *fiber.Ctx
	Client               *http.Client
	Request              *http.Request
	Response             *http.Response
	requestModifications []RequestModification
	resultModifications  []ResponseModification
	htmlTokenRewriters   []rr.IHTMLTokenRewriter
	Ruleset              *ruleset.RuleSet
	debugMode            bool
	abortErr             error
}
=======
type ProxyChain struct {
	Context                 *fiber.Ctx
	Client                  *http.Client
	Request                 *http.Request
	Response                *http.Response
	requestModifications    []RequestModification
	onceRequestModifications []RequestModification
	resultModifications     []ResponseModification
	htmlTokenRewriters      []rr.IHTMLTokenRewriter
	Ruleset                 *ruleset.RuleSet
	debugMode               bool
	abortErr                error
}
>>>>>>> REPLACE
</source>

proxychain/proxychain.go
<source>
<<<<<<< SEARCH
// AddRequestModifications sets the ProxyChain's request modifers
// the modifier will not fire until ProxyChain.Execute() is run.
func (chain *ProxyChain) AddRequestModifications(mods ...RequestModification) *ProxyChain {
	chain.requestModifications = append(chain.requestModifications, mods...)
	return chain
}
=======
// AddRequestModifications adds more request modifers to the ProxyChain
// the modifier will not fire until ProxyChain.Execute() is run.
func (chain *ProxyChain) AddRequestModifications(mods ...RequestModification) *ProxyChain {
	chain.requestModifications = append(chain.requestModifications, mods...)
	return chain
}

// AddOnceRequestModification adds a request modifier to the ProxyChain that should only fire once
// the modifier will not fire until ProxyChain.Execute() is run and will be removed after it has been applied.
func (chain *ProxyChain) AddOnceRequestModification(mod ...RequestModification) *ProxyChain {
	chain.onceRequestModifications = append(chain.onceRequestModifications, mod...)
	return chain
}
>>>>>>> REPLACE
</source>

proxychain/proxychain.go
<source>
<<<<<<< SEARCH
// _execute sends the request for the ProxyChain and returns the raw body only
// the caller is responsible for returning a response back to the requestor
// the caller is also responsible for calling chain._reset() when they are done with the body
func (chain *ProxyChain) _execute() (io.Reader, error) {
	if chain.validateCtxIsSet() != nil || chain.abortErr != nil {
		return nil, chain.abortErr
	}
	if chain.Request == nil {
		return nil, errors.New("proxychain request not yet initialized")
	}
	if chain.Request.URL.Scheme == "" {
		return nil, errors.New("request url not set or invalid. Check ProxyChain ReqMods for issues")
	}

	// Apply requestModifications to proxychain
	for _, applyRequestModificationsTo := range chain.requestModifications {
		err := applyRequestModificationsTo(chain)
		if err != nil {
			return nil, chain.abort(err)
		}
	}
=======
// _execute sends the request for the ProxyChain and returns the raw body only
// the caller is responsible for returning a response back to the requestor
// the caller is also responsible for calling chain._reset() when they are done with the body
func (chain *ProxyChain) _execute() (io.Reader, error) {
	if chain.validateCtxIsSet() != nil || chain.abortErr != nil {
		return nil, chain.abortErr
	}
	if chain.Request == nil {
		return nil, errors.New("proxychain request not yet initialized")
	}
	if chain.Request.URL.Scheme == "" {
		return nil, errors.New("request url not set or invalid. Check ProxyChain ReqMods for issues")
	}

	// Apply requestModifications to proxychain
	for _, applyRequestModificationsTo := range chain.requestModifications {
		err := applyRequestModificationsTo(chain)
		if err != nil {
			return nil, chain.abort(err)
		}
	}

	// Apply onceRequestModifications to proxychain and clear them
	for _, applyOnceRequestModificationsTo := range chain.onceRequestModifications {
		err := applyOnceRequestModificationsTo(chain)
		if err != nil {
			return nil, chain.abort(err)
		}
	}
	chain.onceRequestModifications = nil
>>>>>>> REPLACE
</source>

proxychain/proxychain.go

@@ -83,16 +83,17 @@ proxychain.NewProxyChain().
 └─────────┘    └────────────────────────┘    └─────────┘
 */
 type ProxyChain struct {
-	Context              *fiber.Ctx
-	Client               *http.Client
-	Request              *http.Request
-	Response             *http.Response
-	requestModifications []RequestModification
-	resultModifications  []ResponseModification
-	htmlTokenRewriters   []rr.IHTMLTokenRewriter
-	Ruleset              *ruleset.RuleSet
-	debugMode            bool
-	abortErr             error
+	Context                 *fiber.Ctx
+	Client                  *http.Client
+	Request                 *http.Request
+	Response                *http.Response
+	requestModifications    []RequestModification
+	onceRequestModifications []RequestModification
+	resultModifications     []ResponseModification
+	htmlTokenRewriters      []rr.IHTMLTokenRewriter
+	Ruleset                 *ruleset.RuleSet
+	debugMode               bool
+	abortErr                error
 }
 
 // a ProxyStrategy is a pre-built proxychain with purpose-built defaults
@@ -113,13 +114,20 @@ func (chain *ProxyChain) SetRequestModifications(mods ...RequestModification) *P
 	return chain
 }
 
-// AddRequestModifications sets the ProxyChain's request modifers
+// AddRequestModifications adds more request modifers to the ProxyChain
 // the modifier will not fire until ProxyChain.Execute() is run.
 func (chain *ProxyChain) AddRequestModifications(mods ...RequestModification) *ProxyChain {
 	chain.requestModifications = append(chain.requestModifications, mods...)
 	return chain
 }
 
+// AddOnceRequestModification adds a request modifier to the ProxyChain that should only fire once
+// the modifier will not fire until ProxyChain.Execute() is run and will be removed after it has been applied.
+func (chain *ProxyChain) AddOnceRequestModification(mod ...RequestModification) *ProxyChain {
+	chain.onceRequestModifications = append(chain.onceRequestModifications, mod...)
+	return chain
+}
+
 // AddResponseModifications sets the ProxyChain's response modifers
 // the modifier will not fire until ProxyChain.Execute() is run.
 func (chain *ProxyChain) AddResponseModifications(mods ...ResponseModification) *ProxyChain {
@@ -357,6 +365,15 @@ func (chain *ProxyChain) _execute() (io.Reader, error) {
 		}
 	}
 
+	// Apply onceRequestModifications to proxychain and clear them
+	for _, applyOnceRequestModificationsTo := range chain.onceRequestModifications {
+		err := applyOnceRequestModificationsTo(chain)
+		if err != nil {
+			return nil, chain.abort(err)
+		}
+	}
+	chain.onceRequestModifications = nil
+
 	// Send Request Upstream
 	resp, err := chain.Client.Do(chain.Request)
 	if err != nil {