internal/runtime/executor/token_helpers.go

package executor

import (
	"fmt"
	"regexp"
	"strconv"
	"strings"
	"sync"

	"github.com/tidwall/gjson"
	"github.com/tiktoken-go/tokenizer"
)

// tokenizerCache stores tokenizer instances to avoid repeated creation
var tokenizerCache sync.Map

// TokenizerWrapper wraps a tokenizer codec with an adjustment factor for models
// where tiktoken may not accurately estimate token counts (e.g., Claude models)
type TokenizerWrapper struct {
	Codec            tokenizer.Codec
	AdjustmentFactor float64 // 1.0 means no adjustment, >1.0 means tiktoken underestimates
}

// Count returns the token count with adjustment factor applied
func (tw *TokenizerWrapper) Count(text string) (int, error) {
	count, err := tw.Codec.Count(text)
	if err != nil {
		return 0, err
	}
	if tw.AdjustmentFactor != 1.0 && tw.AdjustmentFactor > 0 {
		return int(float64(count) * tw.AdjustmentFactor), nil
	}
	return count, nil
}

// getTokenizer returns a cached tokenizer for the given model.
// This improves performance by avoiding repeated tokenizer creation.
func getTokenizer(model string) (*TokenizerWrapper, error) {
	// Check cache first
	if cached, ok := tokenizerCache.Load(model); ok {
		return cached.(*TokenizerWrapper), nil
	}

	// Cache miss, create new tokenizer
	wrapper, err := tokenizerForModel(model)
	if err != nil {
		return nil, err
	}

	// Store in cache (use LoadOrStore to handle race conditions)
	actual, _ := tokenizerCache.LoadOrStore(model, wrapper)
	return actual.(*TokenizerWrapper), nil
}

// tokenizerForModel returns a tokenizer codec suitable for an OpenAI-style model id.
// For Claude models, applies a 1.1 adjustment factor since tiktoken may underestimate.
func tokenizerForModel(model string) (*TokenizerWrapper, error) {
	sanitized := strings.ToLower(strings.TrimSpace(model))

	// Claude models use cl100k_base with 1.1 adjustment factor
	// because tiktoken may underestimate Claude's actual token count
	if strings.Contains(sanitized, "claude") || strings.HasPrefix(sanitized, "kiro-") || strings.HasPrefix(sanitized, "amazonq-") {
		enc, err := tokenizer.Get(tokenizer.Cl100kBase)
		if err != nil {
			return nil, err
		}
		return &TokenizerWrapper{Codec: enc, AdjustmentFactor: 1.1}, nil
	}

	var enc tokenizer.Codec
	var err error

	switch {
	case sanitized == "":
		enc, err = tokenizer.Get(tokenizer.Cl100kBase)
	case strings.HasPrefix(sanitized, "gpt-5.2"):
		enc, err = tokenizer.Get(tokenizer.Cl100kBase)
	case strings.HasPrefix(sanitized, "gpt-5.1"):
		enc, err = tokenizer.Get(tokenizer.Cl100kBase)
	case strings.HasPrefix(sanitized, "gpt-5"):
		enc, err = tokenizer.Get(tokenizer.Cl100kBase)
	case strings.HasPrefix(sanitized, "gpt-4.1"):
		enc, err = tokenizer.Get(tokenizer.Cl100kBase)
	case strings.HasPrefix(sanitized, "gpt-4o"):
		enc, err = tokenizer.ForModel(tokenizer.GPT4o)
	case strings.HasPrefix(sanitized, "gpt-4"):
		enc, err = tokenizer.ForModel(tokenizer.GPT4)
	case strings.HasPrefix(sanitized, "gpt-3.5"), strings.HasPrefix(sanitized, "gpt-3"):
		enc, err = tokenizer.ForModel(tokenizer.GPT35Turbo)
	case strings.HasPrefix(sanitized, "o1"):
		enc, err = tokenizer.Get(tokenizer.Cl100kBase)
	case strings.HasPrefix(sanitized, "o3"):
		enc, err = tokenizer.Get(tokenizer.Cl100kBase)
	case strings.HasPrefix(sanitized, "o4"):
		enc, err = tokenizer.Get(tokenizer.Cl100kBase)
	default:
		enc, err = tokenizer.Get(tokenizer.O200kBase)
	}

	if err != nil {
		return nil, err
	}
	return &TokenizerWrapper{Codec: enc, AdjustmentFactor: 1.0}, nil
}

// countOpenAIChatTokens approximates prompt tokens for OpenAI chat completions payloads.
func countOpenAIChatTokens(enc *TokenizerWrapper, payload []byte) (int64, error) {
	if enc == nil {
		return 0, fmt.Errorf("encoder is nil")
	}
	if len(payload) == 0 {
		return 0, nil
	}

	root := gjson.ParseBytes(payload)
	segments := make([]string, 0, 32)

	collectOpenAIMessages(root.Get("messages"), &segments)
	collectOpenAITools(root.Get("tools"), &segments)
	collectOpenAIFunctions(root.Get("functions"), &segments)
	collectOpenAIToolChoice(root.Get("tool_choice"), &segments)
	collectOpenAIResponseFormat(root.Get("response_format"), &segments)
	addIfNotEmpty(&segments, root.Get("input").String())
	addIfNotEmpty(&segments, root.Get("prompt").String())

	joined := strings.TrimSpace(strings.Join(segments, "\n"))
	if joined == "" {
		return 0, nil
	}

	// Count text tokens
	count, err := enc.Count(joined)
	if err != nil {
		return 0, err
	}

	// Extract and add image tokens from placeholders
	imageTokens := extractImageTokens(joined)

	return int64(count) + int64(imageTokens), nil
}

// countClaudeChatTokens approximates prompt tokens for Claude API chat completions payloads.
// This handles Claude's message format with system, messages, and tools.
// Image tokens are estimated based on image dimensions when available.
func countClaudeChatTokens(enc *TokenizerWrapper, payload []byte) (int64, error) {
	if enc == nil {
		return 0, fmt.Errorf("encoder is nil")
	}
	if len(payload) == 0 {
		return 0, nil
	}

	root := gjson.ParseBytes(payload)
	segments := make([]string, 0, 32)

	// Collect system prompt (can be string or array of content blocks)
	collectClaudeSystem(root.Get("system"), &segments)

	// Collect messages
	collectClaudeMessages(root.Get("messages"), &segments)

	// Collect tools
	collectClaudeTools(root.Get("tools"), &segments)

	joined := strings.TrimSpace(strings.Join(segments, "\n"))
	if joined == "" {
		return 0, nil
	}

	// Count text tokens
	count, err := enc.Count(joined)
	if err != nil {
		return 0, err
	}

	// Extract and add image tokens from placeholders
	imageTokens := extractImageTokens(joined)

	return int64(count) + int64(imageTokens), nil
}

// imageTokenPattern matches [IMAGE:xxx tokens] format for extracting estimated image tokens
var imageTokenPattern = regexp.MustCompile(`\[IMAGE:(\d+) tokens\]`)

// extractImageTokens extracts image token estimates from placeholder text.
// Placeholders are in the format [IMAGE:xxx tokens] where xxx is the estimated token count.
func extractImageTokens(text string) int {
	matches := imageTokenPattern.FindAllStringSubmatch(text, -1)
	total := 0
	for _, match := range matches {
		if len(match) > 1 {
			if tokens, err := strconv.Atoi(match[1]); err == nil {
				total += tokens
			}
		}
	}
	return total
}

// estimateImageTokens calculates estimated tokens for an image based on dimensions.
// Based on Claude's image token calculation: tokens ≈ (width * height) / 750
// Minimum 85 tokens, maximum 1590 tokens (for 1568x1568 images).
func estimateImageTokens(width, height float64) int {
	if width <= 0 || height <= 0 {
		// No valid dimensions, use default estimate (medium-sized image)
		return 1000
	}

	tokens := int(width * height / 750)

	// Apply bounds
	if tokens < 85 {
		tokens = 85
	}
	if tokens > 1590 {
		tokens = 1590
	}

	return tokens
}

// collectClaudeSystem extracts text from Claude's system field.
// System can be a string or an array of content blocks.
func collectClaudeSystem(system gjson.Result, segments *[]string) {
	if !system.Exists() {
		return
	}
	if system.Type == gjson.String {
		addIfNotEmpty(segments, system.String())
		return
	}
	if system.IsArray() {
		system.ForEach(func(_, block gjson.Result) bool {
			blockType := block.Get("type").String()
			if blockType == "text" || blockType == "" {
				addIfNotEmpty(segments, block.Get("text").String())
			}
			// Also handle plain string blocks
			if block.Type == gjson.String {
				addIfNotEmpty(segments, block.String())
			}
			return true
		})
	}
}

// collectClaudeMessages extracts text from Claude's messages array.
func collectClaudeMessages(messages gjson.Result, segments *[]string) {
	if !messages.Exists() || !messages.IsArray() {
		return
	}
	messages.ForEach(func(_, message gjson.Result) bool {
		addIfNotEmpty(segments, message.Get("role").String())
		collectClaudeContent(message.Get("content"), segments)
		return true
	})
}

// collectClaudeContent extracts text from Claude's content field.
// Content can be a string or an array of content blocks.
// For images, estimates token count based on dimensions when available.
func collectClaudeContent(content gjson.Result, segments *[]string) {
	if !content.Exists() {
		return
	}
	if content.Type == gjson.String {
		addIfNotEmpty(segments, content.String())
		return
	}
	if content.IsArray() {
		content.ForEach(func(_, part gjson.Result) bool {
			partType := part.Get("type").String()
			switch partType {
			case "text":
				addIfNotEmpty(segments, part.Get("text").String())
			case "image":
				// Estimate image tokens based on dimensions if available
				source := part.Get("source")
				if source.Exists() {
					width := source.Get("width").Float()
					height := source.Get("height").Float()
					if width > 0 && height > 0 {
						tokens := estimateImageTokens(width, height)
						addIfNotEmpty(segments, fmt.Sprintf("[IMAGE:%d tokens]", tokens))
					} else {
						// No dimensions available, use default estimate
						addIfNotEmpty(segments, "[IMAGE:1000 tokens]")
					}
				} else {
					// No source info, use default estimate
					addIfNotEmpty(segments, "[IMAGE:1000 tokens]")
				}
			case "tool_use":
				addIfNotEmpty(segments, part.Get("id").String())
				addIfNotEmpty(segments, part.Get("name").String())
				if input := part.Get("input"); input.Exists() {
					addIfNotEmpty(segments, input.Raw)
				}
			case "tool_result":
				addIfNotEmpty(segments, part.Get("tool_use_id").String())
				collectClaudeContent(part.Get("content"), segments)
			case "thinking":
				addIfNotEmpty(segments, part.Get("thinking").String())
			default:
				// For unknown types, try to extract any text content
				if part.Type == gjson.String {
					addIfNotEmpty(segments, part.String())
				} else if part.Type == gjson.JSON {
					addIfNotEmpty(segments, part.Raw)
				}
			}
			return true
		})
	}
}

// collectClaudeTools extracts text from Claude's tools array.
func collectClaudeTools(tools gjson.Result, segments *[]string) {
	if !tools.Exists() || !tools.IsArray() {
		return
	}
	tools.ForEach(func(_, tool gjson.Result) bool {
		addIfNotEmpty(segments, tool.Get("name").String())
		addIfNotEmpty(segments, tool.Get("description").String())
		if inputSchema := tool.Get("input_schema"); inputSchema.Exists() {
			addIfNotEmpty(segments, inputSchema.Raw)
		}
		return true
	})
}

// buildOpenAIUsageJSON returns a minimal usage structure understood by downstream translators.
func buildOpenAIUsageJSON(count int64) []byte {
	return []byte(fmt.Sprintf(`{"usage":{"prompt_tokens":%d,"completion_tokens":0,"total_tokens":%d}}`, count, count))
}

func collectOpenAIMessages(messages gjson.Result, segments *[]string) {
	if !messages.Exists() || !messages.IsArray() {
		return
	}
	messages.ForEach(func(_, message gjson.Result) bool {
		addIfNotEmpty(segments, message.Get("role").String())
		addIfNotEmpty(segments, message.Get("name").String())
		collectOpenAIContent(message.Get("content"), segments)
		collectOpenAIToolCalls(message.Get("tool_calls"), segments)
		collectOpenAIFunctionCall(message.Get("function_call"), segments)
		return true
	})
}

func collectOpenAIContent(content gjson.Result, segments *[]string) {
	if !content.Exists() {
		return
	}
	if content.Type == gjson.String {
		addIfNotEmpty(segments, content.String())
		return
	}
	if content.IsArray() {
		content.ForEach(func(_, part gjson.Result) bool {
			partType := part.Get("type").String()
			switch partType {
			case "text", "input_text", "output_text":
				addIfNotEmpty(segments, part.Get("text").String())
			case "image_url":
				addIfNotEmpty(segments, part.Get("image_url.url").String())
			case "input_audio", "output_audio", "audio":
				addIfNotEmpty(segments, part.Get("id").String())
			case "tool_result":
				addIfNotEmpty(segments, part.Get("name").String())
				collectOpenAIContent(part.Get("content"), segments)
			default:
				if part.IsArray() {
					collectOpenAIContent(part, segments)
					return true
				}
				if part.Type == gjson.JSON {
					addIfNotEmpty(segments, part.Raw)
					return true
				}
				addIfNotEmpty(segments, part.String())
			}
			return true
		})
		return
	}
	if content.Type == gjson.JSON {
		addIfNotEmpty(segments, content.Raw)
	}
}

func collectOpenAIToolCalls(calls gjson.Result, segments *[]string) {
	if !calls.Exists() || !calls.IsArray() {
		return
	}
	calls.ForEach(func(_, call gjson.Result) bool {
		addIfNotEmpty(segments, call.Get("id").String())
		addIfNotEmpty(segments, call.Get("type").String())
		function := call.Get("function")
		if function.Exists() {
			addIfNotEmpty(segments, function.Get("name").String())
			addIfNotEmpty(segments, function.Get("description").String())
			addIfNotEmpty(segments, function.Get("arguments").String())
			if params := function.Get("parameters"); params.Exists() {
				addIfNotEmpty(segments, params.Raw)
			}
		}
		return true
	})
}

func collectOpenAIFunctionCall(call gjson.Result, segments *[]string) {
	if !call.Exists() {
		return
	}
	addIfNotEmpty(segments, call.Get("name").String())
	addIfNotEmpty(segments, call.Get("arguments").String())
}

func collectOpenAITools(tools gjson.Result, segments *[]string) {
	if !tools.Exists() {
		return
	}
	if tools.IsArray() {
		tools.ForEach(func(_, tool gjson.Result) bool {
			appendToolPayload(tool, segments)
			return true
		})
		return
	}
	appendToolPayload(tools, segments)
}

func collectOpenAIFunctions(functions gjson.Result, segments *[]string) {
	if !functions.Exists() || !functions.IsArray() {
		return
	}
	functions.ForEach(func(_, function gjson.Result) bool {
		addIfNotEmpty(segments, function.Get("name").String())
		addIfNotEmpty(segments, function.Get("description").String())
		if params := function.Get("parameters"); params.Exists() {
			addIfNotEmpty(segments, params.Raw)
		}
		return true
	})
}

func collectOpenAIToolChoice(choice gjson.Result, segments *[]string) {
	if !choice.Exists() {
		return
	}
	if choice.Type == gjson.String {
		addIfNotEmpty(segments, choice.String())
		return
	}
	addIfNotEmpty(segments, choice.Raw)
}

func collectOpenAIResponseFormat(format gjson.Result, segments *[]string) {
	if !format.Exists() {
		return
	}
	addIfNotEmpty(segments, format.Get("type").String())
	addIfNotEmpty(segments, format.Get("name").String())
	if schema := format.Get("json_schema"); schema.Exists() {
		addIfNotEmpty(segments, schema.Raw)
	}
	if schema := format.Get("schema"); schema.Exists() {
		addIfNotEmpty(segments, schema.Raw)
	}
}

func appendToolPayload(tool gjson.Result, segments *[]string) {
	if !tool.Exists() {
		return
	}
	addIfNotEmpty(segments, tool.Get("type").String())
	addIfNotEmpty(segments, tool.Get("name").String())
	addIfNotEmpty(segments, tool.Get("description").String())
	if function := tool.Get("function"); function.Exists() {
		addIfNotEmpty(segments, function.Get("name").String())
		addIfNotEmpty(segments, function.Get("description").String())
		if params := function.Get("parameters"); params.Exists() {
			addIfNotEmpty(segments, params.Raw)
		}
	}
}

func addIfNotEmpty(segments *[]string, value string) {
	if segments == nil {
		return
	}
	if trimmed := strings.TrimSpace(value); trimmed != "" {
		*segments = append(*segments, trimmed)
	}
}