[Refactor]: Core/API Split (#1506)

Refactors api folder to core, creates firm split between backend code and api frontend.

core/http/endpoints/openai/chat.go

@@ -0,0 +1,97 @@
+package openai
+
+import (
+	"bufio"
+	"bytes"
+	"encoding/json"
+	"fmt"
+
+	"github.com/go-skynet/LocalAI/core/backend"
+	"github.com/go-skynet/LocalAI/core/services"
+	"github.com/go-skynet/LocalAI/pkg/model"
+	"github.com/go-skynet/LocalAI/pkg/schema"
+	"github.com/gofiber/fiber/v2"
+	"github.com/rs/zerolog/log"
+	"github.com/valyala/fasthttp"
+)
+
+func ChatEndpoint(cl *services.ConfigLoader, ml *model.ModelLoader, startupOptions *schema.StartupOptions) func(c *fiber.Ctx) error {
+
+	emptyMessage := ""
+
+	return func(c *fiber.Ctx) error {
+		modelName, input, err := readInput(c, startupOptions, ml, true)
+		if err != nil {
+			return fmt.Errorf("failed reading parameters from request:%w", err)
+		}
+
+		// The scary comment I feel like I forgot about along the way:
+		//
+		// functions are not supported in stream mode (yet?)
+		//
+		if input.Stream {
+			log.Debug().Msgf("Stream request received")
+			c.Context().SetContentType("text/event-stream")
+			//c.Response().Header.SetContentType(fiber.MIMETextHTMLCharsetUTF8)
+			//	c.Set("Content-Type", "text/event-stream")
+			c.Set("Cache-Control", "no-cache")
+			c.Set("Connection", "keep-alive")
+			c.Set("Transfer-Encoding", "chunked")
+
+			responses, err := backend.StreamingChatGenerationOpenAIRequest(modelName, input, cl, ml, startupOptions)
+			if err != nil {
+				return fmt.Errorf("failed establishing streaming chat request :%w", err)
+			}
+			c.Context().SetBodyStreamWriter(fasthttp.StreamWriter(func(w *bufio.Writer) {
+				usage := &schema.OpenAIUsage{}
+				id := ""
+				created := 0
+				for ev := range responses {
+					usage = &ev.Usage // Copy a pointer to the latest usage chunk so that the stop message can reference it
+					id = ev.ID
+					created = ev.Created // Similarly, grab the ID and created from any / the last response so we can use it for the stop
+					var buf bytes.Buffer
+					enc := json.NewEncoder(&buf)
+					enc.Encode(ev)
+					log.Debug().Msgf("Sending chunk: %s", buf.String())
+					_, err := fmt.Fprintf(w, "data: %v\n", buf.String())
+					if err != nil {
+						log.Debug().Msgf("Sending chunk failed: %v", err)
+						input.Cancel()
+						break
+					}
+					w.Flush()
+				}
+
+				resp := &schema.OpenAIResponse{
+					ID:      id,
+					Created: created,
+					Model:   input.Model, // we have to return what the user sent here, due to OpenAI spec.
+					Choices: []schema.Choice{
+						{
+							FinishReason: "stop",
+							Index:        0,
+							Delta:        &schema.Message{Content: &emptyMessage},
+						}},
+					Object: "chat.completion.chunk",
+					Usage:  *usage,
+				}
+				respData, _ := json.Marshal(resp)
+
+				w.WriteString(fmt.Sprintf("data: %s\n\n", respData))
+				w.WriteString("data: [DONE]\n\n")
+				w.Flush()
+			}))
+			return nil
+		}
+		//////////////////////////////////////////
+
+		resp, err := backend.ChatGenerationOpenAIRequest(modelName, input, cl, ml, startupOptions)
+		if err != nil {
+			return fmt.Errorf("error generating chat request: +%w", err)
+		}
+		respData, _ := json.Marshal(resp) // TODO this is only used for the debug log and costs performance. monitor this?
+		log.Debug().Msgf("Response: %s", respData)
+		return c.JSON(resp)
+	}
+}