Feat/messages api (#546)

* fix test server setup:
- go map access is not deterministic
- this can lead to a route: /foo/bar/1 matching /foo/bar before matching /foo/bar/1 if the map iteration go through /foo/bar first since the regex match wasn't bound to start and end anchors
- registering handlers now converts * in routes to .* for proper regex matching
- test server route handling now tries to fully match the handler route

* add missing /v1 prefix to fine-tuning job cancel test server handler

* add create message call

* add messages list call

* add get message call

* add modify message call, fix return types for other message calls

* add message file retrieve call

* add list message files call

* code style fixes

* add test for list messages with pagination options

* add beta header to msg calls now that #545 is merged

* Update messages.go

Co-authored-by: Simone Vellei <henomis@gmail.com>

* Update messages.go

Co-authored-by: Simone Vellei <henomis@gmail.com>

* add missing object details for message, fix tests

* fix merge formatting

* minor style fixes

---------

Co-authored-by: Simone Vellei <henomis@gmail.com>

messages.go

@@ -0,0 +1,178 @@
+package openai
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"net/url"
+)
+
+const (
+	messagesSuffix = "messages"
+)
+
+type Message struct {
+	ID          string           `json:"id"`
+	Object      string           `json:"object"`
+	CreatedAt   int              `json:"created_at"`
+	ThreadID    string           `json:"thread_id"`
+	Role        string           `json:"role"`
+	Content     []MessageContent `json:"content"`
+	FileIds     []string         `json:"file_ids"`
+	AssistantID *string          `json:"assistant_id,omitempty"`
+	RunID       *string          `json:"run_id,omitempty"`
+	Metadata    map[string]any   `json:"metadata"`
+
+	httpHeader
+}
+
+type MessagesList struct {
+	Messages []Message `json:"data"`
+
+	httpHeader
+}
+
+type MessageContent struct {
+	Type      string       `json:"type"`
+	Text      *MessageText `json:"text,omitempty"`
+	ImageFile *ImageFile   `json:"image_file,omitempty"`
+}
+type MessageText struct {
+	Value       string `json:"value"`
+	Annotations []any  `json:"annotations"`
+}
+
+type ImageFile struct {
+	FileID string `json:"file_id"`
+}
+
+type MessageRequest struct {
+	Role     string         `json:"role"`
+	Content  string         `json:"content"`
+	FileIds  []string       `json:"file_ids,omitempty"`
+	Metadata map[string]any `json:"metadata,omitempty"`
+}
+
+type MessageFile struct {
+	ID        string `json:"id"`
+	Object    string `json:"object"`
+	CreatedAt int    `json:"created_at"`
+	MessageID string `json:"message_id"`
+
+	httpHeader
+}
+
+type MessageFilesList struct {
+	MessageFiles []MessageFile `json:"data"`
+
+	httpHeader
+}
+
+// CreateMessage creates a new message.
+func (c *Client) CreateMessage(ctx context.Context, threadID string, request MessageRequest) (msg Message, err error) {
+	urlSuffix := fmt.Sprintf("/threads/%s/%s", threadID, messagesSuffix)
+	req, err := c.newRequest(ctx, http.MethodPost, c.fullURL(urlSuffix), withBody(request))
+	if err != nil {
+		return
+	}
+
+	err = c.sendRequest(req, &msg)
+	return
+}
+
+// ListMessage fetches all messages in the thread.
+func (c *Client) ListMessage(ctx context.Context, threadID string,
+	limit *int,
+	order *string,
+	after *string,
+	before *string,
+) (messages MessagesList, err error) {
+	urlValues := url.Values{}
+	if limit != nil {
+		urlValues.Add("limit", fmt.Sprintf("%d", *limit))
+	}
+	if order != nil {
+		urlValues.Add("order", *order)
+	}
+	if after != nil {
+		urlValues.Add("after", *after)
+	}
+	if before != nil {
+		urlValues.Add("before", *before)
+	}
+	encodedValues := ""
+	if len(urlValues) > 0 {
+		encodedValues = "?" + urlValues.Encode()
+	}
+
+	urlSuffix := fmt.Sprintf("/threads/%s/%s%s", threadID, messagesSuffix, encodedValues)
+	req, err := c.newRequest(ctx, http.MethodGet, c.fullURL(urlSuffix), withBetaAssistantV1())
+	if err != nil {
+		return
+	}
+
+	err = c.sendRequest(req, &messages)
+	return
+}
+
+// RetrieveMessage retrieves a Message.
+func (c *Client) RetrieveMessage(
+	ctx context.Context,
+	threadID, messageID string,
+) (msg Message, err error) {
+	urlSuffix := fmt.Sprintf("/threads/%s/%s/%s", threadID, messagesSuffix, messageID)
+	req, err := c.newRequest(ctx, http.MethodGet, c.fullURL(urlSuffix), withBetaAssistantV1())
+	if err != nil {
+		return
+	}
+
+	err = c.sendRequest(req, &msg)
+	return
+}
+
+// ModifyMessage modifies a message.
+func (c *Client) ModifyMessage(
+	ctx context.Context,
+	threadID, messageID string,
+	metadata map[string]any,
+) (msg Message, err error) {
+	urlSuffix := fmt.Sprintf("/threads/%s/%s/%s", threadID, messagesSuffix, messageID)
+	req, err := c.newRequest(ctx, http.MethodPost, c.fullURL(urlSuffix),
+		withBody(metadata), withBetaAssistantV1())
+	if err != nil {
+		return
+	}
+
+	err = c.sendRequest(req, &msg)
+	return
+}
+
+// RetrieveMessageFile fetches a message file.
+func (c *Client) RetrieveMessageFile(
+	ctx context.Context,
+	threadID, messageID, fileID string,
+) (file MessageFile, err error) {
+	urlSuffix := fmt.Sprintf("/threads/%s/%s/%s/files/%s", threadID, messagesSuffix, messageID, fileID)
+	req, err := c.newRequest(ctx, http.MethodGet, c.fullURL(urlSuffix), withBetaAssistantV1())
+	if err != nil {
+		return
+	}
+
+	err = c.sendRequest(req, &file)
+	return
+}
+
+// ListMessageFiles fetches all files attached to a message.
+func (c *Client) ListMessageFiles(
+	ctx context.Context,
+	threadID, messageID string,
+) (files MessageFilesList, err error) {
+	urlSuffix := fmt.Sprintf("/threads/%s/%s/%s/files", threadID, messagesSuffix, messageID)
+	req, err := c.newRequest(ctx, http.MethodGet, c.fullURL(urlSuffix), withBetaAssistantV1())
+	if err != nil {
+		return
+	}
+
+	err = c.sendRequest(req, &files)
+	return
+}