feat(gemini-web): Add conversation affinity selector

internal/provider/gemini-web/conversation/parse.go

@@ -0,0 +1,102 @@
+package conversation
+
+import (
+	"strings"
+
+	"github.com/tidwall/gjson"
+)
+
+// ExtractMessages attempts to build a message list from the inbound request payload.
+func ExtractMessages(handlerType string, raw []byte) []Message {
+	if len(raw) == 0 {
+		return nil
+	}
+	if msgs := extractOpenAIStyle(raw); len(msgs) > 0 {
+		return msgs
+	}
+	if msgs := extractGeminiContents(raw); len(msgs) > 0 {
+		return msgs
+	}
+	return nil
+}
+
+func extractOpenAIStyle(raw []byte) []Message {
+	root := gjson.ParseBytes(raw)
+	messages := root.Get("messages")
+	if !messages.Exists() {
+		return nil
+	}
+	out := make([]Message, 0, 8)
+	messages.ForEach(func(_, entry gjson.Result) bool {
+		role := strings.ToLower(strings.TrimSpace(entry.Get("role").String()))
+		if role == "" {
+			return true
+		}
+		if role == "system" {
+			return true
+		}
+		var contentBuilder strings.Builder
+		content := entry.Get("content")
+		if !content.Exists() {
+			out = append(out, Message{Role: role, Text: ""})
+			return true
+		}
+		switch content.Type {
+		case gjson.String:
+			contentBuilder.WriteString(content.String())
+		case gjson.JSON:
+			if content.IsArray() {
+				content.ForEach(func(_, part gjson.Result) bool {
+					if text := part.Get("text"); text.Exists() {
+						if contentBuilder.Len() > 0 {
+							contentBuilder.WriteString("\n")
+						}
+						contentBuilder.WriteString(text.String())
+					}
+					return true
+				})
+			}
+		}
+		out = append(out, Message{Role: role, Text: contentBuilder.String()})
+		return true
+	})
+	if len(out) == 0 {
+		return nil
+	}
+	return out
+}
+
+func extractGeminiContents(raw []byte) []Message {
+	contents := gjson.GetBytes(raw, "contents")
+	if !contents.Exists() {
+		return nil
+	}
+	out := make([]Message, 0, 8)
+	contents.ForEach(func(_, entry gjson.Result) bool {
+		role := strings.TrimSpace(entry.Get("role").String())
+		if role == "" {
+			role = "user"
+		} else {
+			role = strings.ToLower(role)
+			if role == "model" {
+				role = "assistant"
+			}
+		}
+		var builder strings.Builder
+		entry.Get("parts").ForEach(func(_, part gjson.Result) bool {
+			if text := part.Get("text"); text.Exists() {
+				if builder.Len() > 0 {
+					builder.WriteString("\n")
+				}
+				builder.WriteString(text.String())
+			}
+			return true
+		})
+		out = append(out, Message{Role: role, Text: builder.String()})
+		return true
+	})
+	if len(out) == 0 {
+		return nil
+	}
+	return out
+}