Add Google tool calling

internal/providers/google/google.go

@@ -2,6 +2,7 @@ package google
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
 
 	"github.com/google/uuid"
@@ -76,7 +77,27 @@ func (p *Provider) Generate(ctx context.Context, messages []api.Message, req *ap
 
 	contents, systemText := convertMessages(messages)
 
-	config := buildConfig(systemText, req)
+	// Parse tools if present
+	var tools []*genai.Tool
+	if req.Tools != nil && len(req.Tools) > 0 {
+		var err error
+		tools, err = parseTools(req)
+		if err != nil {
+			return nil, fmt.Errorf("parse tools: %w", err)
+		}
+	}
+
+	// Parse tool_choice if present
+	var toolConfig *genai.ToolConfig
+	if req.ToolChoice != nil && len(req.ToolChoice) > 0 {
+		var err error
+		toolConfig, err = parseToolChoice(req)
+		if err != nil {
+			return nil, fmt.Errorf("parse tool_choice: %w", err)
+		}
+	}
+
+	config := buildConfig(systemText, req, tools, toolConfig)
 
 	resp, err := p.client.Models.GenerateContent(ctx, model, contents, config)
 	if err != nil {
@@ -92,6 +113,11 @@ func (p *Provider) Generate(ctx context.Context, messages []api.Message, req *ap
 		}
 	}
 
+	var toolCalls []api.ToolCall
+	if len(resp.Candidates) > 0 {
+		toolCalls = extractToolCalls(resp)
+	}
+
 	var inputTokens, outputTokens int
 	if resp.UsageMetadata != nil {
 		inputTokens = int(resp.UsageMetadata.PromptTokenCount)
@@ -99,9 +125,10 @@ func (p *Provider) Generate(ctx context.Context, messages []api.Message, req *ap
 	}
 
 	return &api.ProviderResult{
-		ID:    uuid.NewString(),
-		Model: model,
-		Text:  text,
+		ID:        uuid.NewString(),
+		Model:     model,
+		Text:      text,
+		ToolCalls: toolCalls,
 		Usage: api.Usage{
 			InputTokens:  inputTokens,
 			OutputTokens: outputTokens,
@@ -128,7 +155,29 @@ func (p *Provider) GenerateStream(ctx context.Context, messages []api.Message, r
 
 		contents, systemText := convertMessages(messages)
 
-		config := buildConfig(systemText, req)
+		// Parse tools if present
+		var tools []*genai.Tool
+		if req.Tools != nil && len(req.Tools) > 0 {
+			var err error
+			tools, err = parseTools(req)
+			if err != nil {
+				errChan <- fmt.Errorf("parse tools: %w", err)
+				return
+			}
+		}
+
+		// Parse tool_choice if present
+		var toolConfig *genai.ToolConfig
+		if req.ToolChoice != nil && len(req.ToolChoice) > 0 {
+			var err error
+			toolConfig, err = parseToolChoice(req)
+			if err != nil {
+				errChan <- fmt.Errorf("parse tool_choice: %w", err)
+				return
+			}
+		}
+
+		config := buildConfig(systemText, req, tools, toolConfig)
 
 		stream := p.client.Models.GenerateContentStream(ctx, model, contents, config)
 
@@ -138,21 +187,32 @@ func (p *Provider) GenerateStream(ctx context.Context, messages []api.Message, r
 				return
 			}
 
-			var text string
 			if len(resp.Candidates) > 0 && resp.Candidates[0].Content != nil {
-				for _, part := range resp.Candidates[0].Content.Parts {
+				for partIndex, part := range resp.Candidates[0].Content.Parts {
 					if part != nil {
-						text += part.Text
-					}
-				}
-			}
+						// Handle text content
+						if part.Text != "" {
+							select {
+							case deltaChan <- &api.ProviderStreamDelta{Text: part.Text}:
+							case <-ctx.Done():
+								errChan <- ctx.Err()
+								return
+							}
+						}
 
-			if text != "" {
-				select {
-				case deltaChan <- &api.ProviderStreamDelta{Text: text}:
-				case <-ctx.Done():
-					errChan <- ctx.Err()
-					return
+						// Handle tool call content
+						if part.FunctionCall != nil {
+							delta := extractToolCallDelta(part, partIndex)
+							if delta != nil {
+								select {
+								case deltaChan <- &api.ProviderStreamDelta{ToolCallDelta: delta}:
+								case <-ctx.Done():
+									errChan <- ctx.Err()
+									return
+								}
+							}
+						}
+					}
 				}
 			}
 		}
@@ -182,6 +242,39 @@ func convertMessages(messages []api.Message) ([]*genai.Content, string) {
 			continue
 		}
 
+		if msg.Role == "tool" {
+			// Tool results are sent as FunctionResponse in user role message
+			var output string
+			for _, block := range msg.Content {
+				if block.Type == "input_text" || block.Type == "output_text" {
+					output += block.Text
+				}
+			}
+
+			// Parse output as JSON map, or wrap in {"output": "..."} if not JSON
+			var responseMap map[string]any
+			if err := json.Unmarshal([]byte(output), &responseMap); err != nil {
+				// Not JSON, wrap it
+				responseMap = map[string]any{"output": output}
+			}
+
+			// Create FunctionResponse part with CallID from message
+			part := &genai.Part{
+				FunctionResponse: &genai.FunctionResponse{
+					ID:       msg.CallID,
+					Name:     "", // Name is optional for responses
+					Response: responseMap,
+				},
+			}
+
+			// Add to user role message
+			contents = append(contents, &genai.Content{
+				Role:  "user",
+				Parts: []*genai.Part{part},
+			})
+			continue
+		}
+
 		var parts []*genai.Part
 		for _, block := range msg.Content {
 			if block.Type == "input_text" || block.Type == "output_text" {
@@ -204,10 +297,10 @@ func convertMessages(messages []api.Message) ([]*genai.Content, string) {
 }
 
 // buildConfig constructs a GenerateContentConfig from system text and request params.
-func buildConfig(systemText string, req *api.ResponseRequest) *genai.GenerateContentConfig {
+func buildConfig(systemText string, req *api.ResponseRequest, tools []*genai.Tool, toolConfig *genai.ToolConfig) *genai.GenerateContentConfig {
 	var cfg *genai.GenerateContentConfig
 
-	needsCfg := systemText != "" || req.MaxOutputTokens != nil || req.Temperature != nil || req.TopP != nil
+	needsCfg := systemText != "" || req.MaxOutputTokens != nil || req.Temperature != nil || req.TopP != nil || tools != nil || toolConfig != nil
 	if !needsCfg {
 		return nil
 	}
@@ -234,6 +327,14 @@ func buildConfig(systemText string, req *api.ResponseRequest) *genai.GenerateCon
 		cfg.TopP = &tp
 	}
 
+	if tools != nil {
+		cfg.Tools = tools
+	}
+
+	if toolConfig != nil {
+		cfg.ToolConfig = toolConfig
+	}
+
 	return cfg
 }