Feature: #103

feat(gemini): add Gemini thinking configuration support and metadata normalization

- Introduced logic to parse and apply `thinkingBudget` and `include_thoughts` configurations from metadata.
- Enhanced request handling to include normalized Gemini model metadata, preserving the original model identifier.
- Updated Gemini and Gemini-CLI executors to apply thinking configuration based on metadata overrides.
- Refactored handlers to support metadata extraction and cloning during request preparation.

internal/util/gemini_thinking.go

@@ -0,0 +1,181 @@
+package util
+
+import (
+	"encoding/json"
+	"strconv"
+	"strings"
+
+	"github.com/tidwall/sjson"
+)
+
+const (
+	GeminiThinkingBudgetMetadataKey  = "gemini_thinking_budget"
+	GeminiIncludeThoughtsMetadataKey = "gemini_include_thoughts"
+	GeminiOriginalModelMetadataKey   = "gemini_original_model"
+)
+
+func ParseGeminiThinkingSuffix(model string) (string, *int, *bool, bool) {
+	if model == "" {
+		return model, nil, nil, false
+	}
+	lower := strings.ToLower(model)
+	if !strings.HasPrefix(lower, "gemini-") {
+		return model, nil, nil, false
+	}
+
+	if strings.HasSuffix(lower, "-nothinking") {
+		base := model[:len(model)-len("-nothinking")]
+		budgetValue := 0
+		if strings.HasPrefix(lower, "gemini-2.5-pro") {
+			budgetValue = 128
+		}
+		include := false
+		return base, &budgetValue, &include, true
+	}
+
+	idx := strings.LastIndex(lower, "-thinking-")
+	if idx == -1 {
+		return model, nil, nil, false
+	}
+
+	digits := model[idx+len("-thinking-"):]
+	if digits == "" {
+		return model, nil, nil, false
+	}
+	end := len(digits)
+	for i := 0; i < len(digits); i++ {
+		if digits[i] < '0' || digits[i] > '9' {
+			end = i
+			break
+		}
+	}
+	if end == 0 {
+		return model, nil, nil, false
+	}
+	valueStr := digits[:end]
+	value, err := strconv.Atoi(valueStr)
+	if err != nil {
+		return model, nil, nil, false
+	}
+	base := model[:idx]
+	budgetValue := value
+	return base, &budgetValue, nil, true
+}
+
+func ApplyGeminiThinkingConfig(body []byte, budget *int, includeThoughts *bool) []byte {
+	if budget == nil && includeThoughts == nil {
+		return body
+	}
+	updated := body
+	if budget != nil {
+		valuePath := "generationConfig.thinkingConfig.thinkingBudget"
+		rewritten, err := sjson.SetBytes(updated, valuePath, *budget)
+		if err == nil {
+			updated = rewritten
+		}
+	}
+	if includeThoughts != nil {
+		valuePath := "generationConfig.thinkingConfig.include_thoughts"
+		rewritten, err := sjson.SetBytes(updated, valuePath, *includeThoughts)
+		if err == nil {
+			updated = rewritten
+		}
+	}
+	return updated
+}
+
+func ApplyGeminiCLIThinkingConfig(body []byte, budget *int, includeThoughts *bool) []byte {
+	if budget == nil && includeThoughts == nil {
+		return body
+	}
+	updated := body
+	if budget != nil {
+		valuePath := "request.generationConfig.thinkingConfig.thinkingBudget"
+		rewritten, err := sjson.SetBytes(updated, valuePath, *budget)
+		if err == nil {
+			updated = rewritten
+		}
+	}
+	if includeThoughts != nil {
+		valuePath := "request.generationConfig.thinkingConfig.include_thoughts"
+		rewritten, err := sjson.SetBytes(updated, valuePath, *includeThoughts)
+		if err == nil {
+			updated = rewritten
+		}
+	}
+	return updated
+}
+
+func GeminiThinkingFromMetadata(metadata map[string]any) (*int, *bool, bool) {
+	if len(metadata) == 0 {
+		return nil, nil, false
+	}
+	var (
+		budgetPtr  *int
+		includePtr *bool
+		matched    bool
+	)
+	if rawBudget, ok := metadata[GeminiThinkingBudgetMetadataKey]; ok {
+		switch v := rawBudget.(type) {
+		case int:
+			budget := v
+			budgetPtr = &budget
+			matched = true
+		case int32:
+			budget := int(v)
+			budgetPtr = &budget
+			matched = true
+		case int64:
+			budget := int(v)
+			budgetPtr = &budget
+			matched = true
+		case float64:
+			budget := int(v)
+			budgetPtr = &budget
+			matched = true
+		case json.Number:
+			if val, err := v.Int64(); err == nil {
+				budget := int(val)
+				budgetPtr = &budget
+				matched = true
+			}
+		}
+	}
+	if rawInclude, ok := metadata[GeminiIncludeThoughtsMetadataKey]; ok {
+		switch v := rawInclude.(type) {
+		case bool:
+			include := v
+			includePtr = &include
+			matched = true
+		case string:
+			if parsed, err := strconv.ParseBool(v); err == nil {
+				include := parsed
+				includePtr = &include
+				matched = true
+			}
+		case json.Number:
+			if val, err := v.Int64(); err == nil {
+				include := val != 0
+				includePtr = &include
+				matched = true
+			}
+		case int:
+			include := v != 0
+			includePtr = &include
+			matched = true
+		case int32:
+			include := v != 0
+			includePtr = &include
+			matched = true
+		case int64:
+			include := v != 0
+			includePtr = &include
+			matched = true
+		case float64:
+			include := v != 0
+			includePtr = &include
+			matched = true
+		}
+	}
+	return budgetPtr, includePtr, matched
+}