From e9f89a0b2902f40caf3edcce9a5ee8f8331ab140 Mon Sep 17 00:00:00 2001
From: Rhett Garber <rhettg@gmail.com>
Date: Thu, 17 Aug 2023 21:19:00 +0000
Subject: [PATCH 1/2] Add support for function calling

As described in
https://platform.openai.com/docs/guides/gpt/function-calling some models
have been fine tuned to call functions based on their JSON
representations.
---
 chat/chat.go     | 10 +++++++---
 chat/function.go | 41 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+), 3 deletions(-)
 create mode 100644 chat/function.go

diff --git a/chat/chat.go b/chat/chat.go
index ad8a2f3..ecf3373 100644
--- a/chat/chat.go
+++ b/chat/chat.go
@@ -42,6 +42,9 @@ type CreateCompletionParams struct {
 	Stop     []string   `json:"stop,omitempty"`
 	Stream   bool       `json:"stream,omitempty"`
 
+	Functions    []Function `json:"functions,omitempty"`
+	FunctionCall string     `json:"function_call,omitempty"`
+
 	N           int     `json:"n,omitempty"`
 	TopP        float64 `json:"top_p,omitempty"`
 	Temperature float64 `json:"temperature,omitempty"`
@@ -70,9 +73,10 @@ type Choice struct {
 }
 
 type Message struct {
-	Role    string `json:"role,omitempty"`
-	Content string `json:"content,omitempty"`
-	Name    string `json:"name,omitempty"`
+	Role         string        `json:"role,omitempty"`
+	Content      string        `json:"content,omitempty"`
+	Name         string        `json:"name,omitempty"`
+	FunctionCall *FunctionCall `json:"function_call,omitempty"`
 }
 
 func (c *Client) CreateCompletion(ctx context.Context, p *CreateCompletionParams) (*CreateCompletionResponse, error) {
diff --git a/chat/function.go b/chat/function.go
new file mode 100644
index 0000000..d95499e
--- /dev/null
+++ b/chat/function.go
@@ -0,0 +1,41 @@
+package chat
+
+// EmptyParameters is an empty parameter object used for a Function that accepts no arguments.
+var EmptyParameters = Schema{
+	Type:       "object",
+	Properties: map[string]Schema{},
+}
+
+const (
+	// FunctionCallAuto indicates the model should decide whether to call the function.
+	// This is default when Functions are provided.
+	FunctionCallAuto = "auto"
+
+	// FunctionCallNone indicates the mode should not call any functions.
+	// This is the default when no Functions are provided.
+	FunctionCallNone = "none"
+)
+
+// Schema defines a schema for a JSON object.
+//
+// See https://json-schema.org/understanding-json-schema/
+type Schema struct {
+	Type        string            `json:"type"`
+	Description string            `json:"description,omitempty"`
+	Properties  map[string]Schema `json:"properties,omitempty"`
+	Required    []string          `json:"required,omitempty"`
+}
+
+// Function is a function the model may generate JSON inputs for
+type Function struct {
+	Name        string `json:"name"`
+	Description string `json:"description,omitempty"`
+	Parameters  Schema `json:"parameters"`
+}
+
+// FunctionCall is the name and arguments of a function that should be called,
+// as generated by the model.
+type FunctionCall struct {
+	Name      string `json:"name"`
+	Arguments string `json:"arguments"`
+}

From fec2047620a29eb836430a6e383639be72768948 Mon Sep 17 00:00:00 2001
From: Rhett Garber <rhettg@gmail.com>
Date: Thu, 17 Aug 2023 22:33:20 +0000
Subject: [PATCH 2/2] Support empty parameter objects

To indicate an empty parameter, the properties must be emitted as `{}`.
But we also need a nil properties field to not be emitted at all. This
is not handled by `omitempty` because it treats nil and empty as the
same.
---
 chat/function.go | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/chat/function.go b/chat/function.go
index d95499e..3c4cc45 100644
--- a/chat/function.go
+++ b/chat/function.go
@@ -1,5 +1,7 @@
 package chat
 
+import "encoding/json"
+
 // EmptyParameters is an empty parameter object used for a Function that accepts no arguments.
 var EmptyParameters = Schema{
 	Type:       "object",
@@ -22,8 +24,32 @@ const (
 type Schema struct {
 	Type        string            `json:"type"`
 	Description string            `json:"description,omitempty"`
-	Properties  map[string]Schema `json:"properties,omitempty"`
+	Properties  map[string]Schema `json:"properties"`
 	Required    []string          `json:"required,omitempty"`
+
+	// NOTE adding new fields may require updating the MarshalJSON method.
+}
+
+func (s Schema) MarshalJSON() ([]byte, error) {
+	type Alias Schema
+
+	// If Properties is nil marshal it without the Properties field.  This,
+	// rather than relying on omitempty, allows us to distinguish between an
+	// empty map (which is needed for valid API requests) and a nil map (which
+	// is needed for the default value).
+	if s.Properties == nil {
+		return json.Marshal(&struct {
+			Type        string   `json:"type"`
+			Description string   `json:"description,omitempty"`
+			Required    []string `json:"required,omitempty"`
+		}{
+			Type:        s.Type,
+			Description: s.Description,
+			Required:    s.Required,
+		})
+	}
+
+	return json.Marshal((*Alias)(&s))
 }
 
 // Function is a function the model may generate JSON inputs for