package antigravity

import (
	"crypto/sha256"
	"encoding/binary"
	"encoding/json"
	"fmt"
	"log"
	"math/rand"
	"os"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/gin-gonic/gin"
	"github.com/google/uuid"
)

var (
	sessionRand      = rand.New(rand.NewSource(time.Now().UnixNano()))
	sessionRandMutex sync.Mutex
)

// generateStableSessionID 基于用户消息内容生成稳定的 session ID
func generateStableSessionID(contents []GeminiContent) string {
	// 查找第一个 user 消息的文本
	for _, content := range contents {
		if content.Role == "user" && len(content.Parts) > 0 {
			if text := content.Parts[0].Text; text != "" {
				h := sha256.Sum256([]byte(text))
				n := int64(binary.BigEndian.Uint64(h[:8])) & 0x7FFFFFFFFFFFFFFF
				return "-" + strconv.FormatInt(n, 10)
			}
		}
	}
	// 回退：生成随机 session ID
	sessionRandMutex.Lock()
	n := sessionRand.Int63n(9_000_000_000_000_000_000)
	sessionRandMutex.Unlock()
	return "-" + strconv.FormatInt(n, 10)
}

type TransformOptions struct {
	EnableIdentityPatch bool
	// IdentityPatch 可选：自定义注入到 systemInstruction 开头的身份防护提示词；
	// 为空时使用默认模板（包含 [IDENTITY_PATCH] 及 SYSTEM_PROMPT_BEGIN 标记）。
	IdentityPatch string
}

func DefaultTransformOptions() TransformOptions {
	return TransformOptions{
		EnableIdentityPatch: true,
	}
}

// TransformClaudeToGemini 将 Claude 请求转换为 v1internal Gemini 格式
func TransformClaudeToGemini(claudeReq *ClaudeRequest, projectID, mappedModel string) ([]byte, error) {
	return TransformClaudeToGeminiWithOptions(claudeReq, projectID, mappedModel, DefaultTransformOptions())
}

// TransformClaudeToGeminiWithOptions 将 Claude 请求转换为 v1internal Gemini 格式（可配置身份补丁等行为）
func TransformClaudeToGeminiWithOptions(claudeReq *ClaudeRequest, projectID, mappedModel string, opts TransformOptions) ([]byte, error) {
	// 用于存储 tool_use id -> name 映射
	toolIDToName := make(map[string]string)

	// 检测是否启用 thinking
	isThinkingEnabled := claudeReq.Thinking != nil && claudeReq.Thinking.Type == "enabled"

	// 只有 Gemini 模型支持 dummy thought workaround
	// Claude 模型通过 Vertex/Google API 需要有效的 thought signatures
	allowDummyThought := strings.HasPrefix(mappedModel, "gemini-")

	// 1. 构建 contents
	contents, strippedThinking, err := buildContents(claudeReq.Messages, toolIDToName, isThinkingEnabled, allowDummyThought)
	if err != nil {
		return nil, fmt.Errorf("build contents: %w", err)
	}

	// 2. 构建 systemInstruction
	systemInstruction := buildSystemInstruction(claudeReq.System, claudeReq.Model, opts)

	// 3. 构建 generationConfig
	reqForConfig := claudeReq
	if strippedThinking {
		// If we had to downgrade thinking blocks to plain text due to missing/invalid signatures,
		// disable upstream thinking mode to avoid signature/structure validation errors.
		reqCopy := *claudeReq
		reqCopy.Thinking = nil
		reqForConfig = &reqCopy
	}
	generationConfig := buildGenerationConfig(reqForConfig)

	// 4. 构建 tools
	tools := buildTools(claudeReq.Tools)

	// 5. 构建内部请求
	innerRequest := GeminiRequest{
		Contents: contents,
		// 总是设置 toolConfig，与官方客户端一致
		ToolConfig: &GeminiToolConfig{
			FunctionCallingConfig: &GeminiFunctionCallingConfig{
				Mode: "VALIDATED",
			},
		},
		// 总是生成 sessionId，基于用户消息内容
		SessionID: generateStableSessionID(contents),
	}

	if systemInstruction != nil {
		innerRequest.SystemInstruction = systemInstruction
	}
	if generationConfig != nil {
		innerRequest.GenerationConfig = generationConfig
	}
	if len(tools) > 0 {
		innerRequest.Tools = tools
	}

	// 如果提供了 metadata.user_id，优先使用
	if claudeReq.Metadata != nil && claudeReq.Metadata.UserID != "" {
		innerRequest.SessionID = claudeReq.Metadata.UserID
	}

	// 6. 包装为 v1internal 请求
	v1Req := V1InternalRequest{
		Project:     projectID,
		RequestID:   "agent-" + uuid.New().String(),
		UserAgent:   "antigravity", // 固定值，与官方客户端一致
		RequestType: "agent",
		Model:       mappedModel,
		Request:     innerRequest,
	}

	return json.Marshal(v1Req)
}

// antigravityIdentity Antigravity identity 提示词
const antigravityIdentity = `<identity>
You are Antigravity, a powerful agentic AI coding assistant designed by the Google Deepmind team working on Advanced Agentic Coding.
You are pair programming with a USER to solve their coding task. The task may require creating a new codebase, modifying or debugging an existing codebase, or simply answering a question.
The USER will send you requests, which you must always prioritize addressing. Along with each USER request, we will attach additional metadata about their current state, such as what files they have open and where their cursor is.
This information may or may not be relevant to the coding task, it is up for you to decide.
</identity>
<communication_style>
- **Proactiveness**. As an agent, you are allowed to be proactive, but only in the course of completing the user's task. For example, if the user asks you to add a new component, you can edit the code, verify build and test statuses, and take any other obvious follow-up actions, such as performing additional research. However, avoid surprising the user. For example, if the user asks HOW to approach something, you should answer their question and instead of jumping into editing a file.</communication_style>`

func defaultIdentityPatch(_ string) string {
	return antigravityIdentity
}

// GetDefaultIdentityPatch 返回默认的 Antigravity 身份提示词
func GetDefaultIdentityPatch() string {
	return antigravityIdentity
}

// buildSystemInstruction 构建 systemInstruction
func buildSystemInstruction(system json.RawMessage, modelName string, opts TransformOptions) *GeminiContent {
	var parts []GeminiPart

	// 先解析用户的 system prompt，检测是否已包含 Antigravity identity
	userHasAntigravityIdentity := false
	var userSystemParts []GeminiPart

	if len(system) > 0 {
		// 尝试解析为字符串
		var sysStr string
		if err := json.Unmarshal(system, &sysStr); err == nil {
			if strings.TrimSpace(sysStr) != "" {
				userSystemParts = append(userSystemParts, GeminiPart{Text: sysStr})
				if strings.Contains(sysStr, "You are Antigravity") {
					userHasAntigravityIdentity = true
				}
			}
		} else {
			// 尝试解析为数组
			var sysBlocks []SystemBlock
			if err := json.Unmarshal(system, &sysBlocks); err == nil {
				for _, block := range sysBlocks {
					if block.Type == "text" && strings.TrimSpace(block.Text) != "" {
						userSystemParts = append(userSystemParts, GeminiPart{Text: block.Text})
						if strings.Contains(block.Text, "You are Antigravity") {
							userHasAntigravityIdentity = true
						}
					}
				}
			}
		}
	}

	// 仅在用户未提供 Antigravity identity 时注入
	if opts.EnableIdentityPatch && !userHasAntigravityIdentity {
		identityPatch := strings.TrimSpace(opts.IdentityPatch)
		if identityPatch == "" {
			identityPatch = defaultIdentityPatch(modelName)
		}
		parts = append(parts, GeminiPart{Text: identityPatch})
	}

	// 添加用户的 system prompt
	parts = append(parts, userSystemParts...)

	if len(parts) == 0 {
		return nil
	}

	return &GeminiContent{
		Role:  "user",
		Parts: parts,
	}
}

// buildContents 构建 contents
func buildContents(messages []ClaudeMessage, toolIDToName map[string]string, isThinkingEnabled, allowDummyThought bool) ([]GeminiContent, bool, error) {
	var contents []GeminiContent
	strippedThinking := false

	for i, msg := range messages {
		role := msg.Role
		if role == "assistant" {
			role = "model"
		}

		parts, strippedThisMsg, err := buildParts(msg.Content, toolIDToName, allowDummyThought)
		if err != nil {
			return nil, false, fmt.Errorf("build parts for message %d: %w", i, err)
		}
		if strippedThisMsg {
			strippedThinking = true
		}

		// 只有 Gemini 模型支持 dummy thinking block workaround
		// 只对最后一条 assistant 消息添加（Pre-fill 场景）
		// 历史 assistant 消息不能添加没有 signature 的 dummy thinking block
		if allowDummyThought && role == "model" && isThinkingEnabled && i == len(messages)-1 {
			hasThoughtPart := false
			for _, p := range parts {
				if p.Thought {
					hasThoughtPart = true
					break
				}
			}
			if !hasThoughtPart && len(parts) > 0 {
				// 在开头添加 dummy thinking block
				parts = append([]GeminiPart{{
					Text:             "Thinking...",
					Thought:          true,
					ThoughtSignature: dummyThoughtSignature,
				}}, parts...)
			}
		}

		if len(parts) == 0 {
			continue
		}

		contents = append(contents, GeminiContent{
			Role:  role,
			Parts: parts,
		})
	}

	return contents, strippedThinking, nil
}

// dummyThoughtSignature 用于跳过 Gemini 3 thought_signature 验证
// 参考: https://ai.google.dev/gemini-api/docs/thought-signatures
const dummyThoughtSignature = "skip_thought_signature_validator"

// buildParts 构建消息的 parts
// allowDummyThought: 只有 Gemini 模型支持 dummy thought signature
func buildParts(content json.RawMessage, toolIDToName map[string]string, allowDummyThought bool) ([]GeminiPart, bool, error) {
	var parts []GeminiPart
	strippedThinking := false

	// 尝试解析为字符串
	var textContent string
	if err := json.Unmarshal(content, &textContent); err == nil {
		if textContent != "(no content)" && strings.TrimSpace(textContent) != "" {
			parts = append(parts, GeminiPart{Text: strings.TrimSpace(textContent)})
		}
		return parts, false, nil
	}

	// 解析为内容块数组
	var blocks []ContentBlock
	if err := json.Unmarshal(content, &blocks); err != nil {
		return nil, false, fmt.Errorf("parse content blocks: %w", err)
	}

	for _, block := range blocks {
		switch block.Type {
		case "text":
			if block.Text != "(no content)" && strings.TrimSpace(block.Text) != "" {
				parts = append(parts, GeminiPart{Text: block.Text})
			}

		case "thinking":
			part := GeminiPart{
				Text:    block.Thinking,
				Thought: true,
			}
			// 保留原有 signature（Claude 模型需要有效的 signature）
			if block.Signature != "" {
				part.ThoughtSignature = block.Signature
			} else if !allowDummyThought {
				// Claude 模型需要有效 signature；在缺失时降级为普通文本，并在上层禁用 thinking mode。
				if strings.TrimSpace(block.Thinking) != "" {
					parts = append(parts, GeminiPart{Text: block.Thinking})
				}
				strippedThinking = true
				continue
			} else {
				// Gemini 模型使用 dummy signature
				part.ThoughtSignature = dummyThoughtSignature
			}
			parts = append(parts, part)

		case "image":
			if block.Source != nil && block.Source.Type == "base64" {
				parts = append(parts, GeminiPart{
					InlineData: &GeminiInlineData{
						MimeType: block.Source.MediaType,
						Data:     block.Source.Data,
					},
				})
			}

		case "tool_use":
			// 存储 id -> name 映射
			if block.ID != "" && block.Name != "" {
				toolIDToName[block.ID] = block.Name
			}

			part := GeminiPart{
				FunctionCall: &GeminiFunctionCall{
					Name: block.Name,
					Args: block.Input,
					ID:   block.ID,
				},
			}
			// tool_use 的 signature 处理：
			// - Gemini 模型：使用 dummy signature（跳过 thought_signature 校验）
			// - Claude 模型：透传上游返回的真实 signature（Vertex/Google 需要完整签名链路）
			if allowDummyThought {
				part.ThoughtSignature = dummyThoughtSignature
			} else if block.Signature != "" && block.Signature != dummyThoughtSignature {
				part.ThoughtSignature = block.Signature
			}
			parts = append(parts, part)

		case "tool_result":
			// 获取函数名
			funcName := block.Name
			if funcName == "" {
				if name, ok := toolIDToName[block.ToolUseID]; ok {
					funcName = name
				} else {
					funcName = block.ToolUseID
				}
			}

			// 解析 content
			resultContent := parseToolResultContent(block.Content, block.IsError)

			parts = append(parts, GeminiPart{
				FunctionResponse: &GeminiFunctionResponse{
					Name: funcName,
					Response: map[string]any{
						"result": resultContent,
					},
					ID: block.ToolUseID,
				},
			})
		}
	}

	return parts, strippedThinking, nil
}

// parseToolResultContent 解析 tool_result 的 content
func parseToolResultContent(content json.RawMessage, isError bool) string {
	if len(content) == 0 {
		if isError {
			return "Tool execution failed with no output."
		}
		return "Command executed successfully."
	}

	// 尝试解析为字符串
	var str string
	if err := json.Unmarshal(content, &str); err == nil {
		if strings.TrimSpace(str) == "" {
			if isError {
				return "Tool execution failed with no output."
			}
			return "Command executed successfully."
		}
		return str
	}

	// 尝试解析为数组
	var arr []map[string]any
	if err := json.Unmarshal(content, &arr); err == nil {
		var texts []string
		for _, item := range arr {
			if text, ok := item["text"].(string); ok {
				texts = append(texts, text)
			}
		}
		result := strings.Join(texts, "\n")
		if strings.TrimSpace(result) == "" {
			if isError {
				return "Tool execution failed with no output."
			}
			return "Command executed successfully."
		}
		return result
	}

	// 返回原始 JSON
	return string(content)
}

// buildGenerationConfig 构建 generationConfig
func buildGenerationConfig(req *ClaudeRequest) *GeminiGenerationConfig {
	config := &GeminiGenerationConfig{
		MaxOutputTokens: 64000, // 默认最大输出
		StopSequences:   DefaultStopSequences,
	}

	// Thinking 配置
	if req.Thinking != nil && req.Thinking.Type == "enabled" {
		config.ThinkingConfig = &GeminiThinkingConfig{
			IncludeThoughts: true,
		}
		if req.Thinking.BudgetTokens > 0 {
			budget := req.Thinking.BudgetTokens
			// gemini-2.5-flash 上限 24576
			if strings.Contains(req.Model, "gemini-2.5-flash") && budget > 24576 {
				budget = 24576
			}
			config.ThinkingConfig.ThinkingBudget = budget
		}
	}

	// 其他参数
	if req.Temperature != nil {
		config.Temperature = req.Temperature
	}
	if req.TopP != nil {
		config.TopP = req.TopP
	}
	if req.TopK != nil {
		config.TopK = req.TopK
	}

	return config
}

// buildTools 构建 tools
func buildTools(tools []ClaudeTool) []GeminiToolDeclaration {
	if len(tools) == 0 {
		return nil
	}

	// 检查是否有 web_search 工具
	hasWebSearch := false
	for _, tool := range tools {
		if tool.Name == "web_search" {
			hasWebSearch = true
			break
		}
	}

	if hasWebSearch {
		// Web Search 工具映射
		return []GeminiToolDeclaration{{
			GoogleSearch: &GeminiGoogleSearch{
				EnhancedContent: &GeminiEnhancedContent{
					ImageSearch: &GeminiImageSearch{
						MaxResultCount: 5,
					},
				},
			},
		}}
	}

	// 普通工具
	var funcDecls []GeminiFunctionDecl
	for _, tool := range tools {
		// 跳过无效工具名称
		if strings.TrimSpace(tool.Name) == "" {
			log.Printf("Warning: skipping tool with empty name")
			continue
		}

		var description string
		var inputSchema map[string]any

		// 检查是否为 custom 类型工具 (MCP)
		if tool.Type == "custom" {
			if tool.Custom == nil || tool.Custom.InputSchema == nil {
				log.Printf("[Warning] Skipping invalid custom tool '%s': missing custom spec or input_schema", tool.Name)
				continue
			}
			description = tool.Custom.Description
			inputSchema = tool.Custom.InputSchema

		} else {
			// 标准格式: 从顶层字段获取
			description = tool.Description
			inputSchema = tool.InputSchema
		}

		// 清理 JSON Schema
		params := cleanJSONSchema(inputSchema)
		// 为 nil schema 提供默认值
		if params == nil {
			params = map[string]any{
				"type":       "OBJECT",
				"properties": map[string]any{},
			}
		}

		funcDecls = append(funcDecls, GeminiFunctionDecl{
			Name:        tool.Name,
			Description: description,
			Parameters:  params,
		})
	}

	if len(funcDecls) == 0 {
		return nil
	}

	return []GeminiToolDeclaration{{
		FunctionDeclarations: funcDecls,
	}}
}

// cleanJSONSchema 清理 JSON Schema，移除 Antigravity/Gemini 不支持的字段
// 参考 proxycast 的实现，确保 schema 符合 JSON Schema draft 2020-12
func cleanJSONSchema(schema map[string]any) map[string]any {
	if schema == nil {
		return nil
	}
	cleaned := cleanSchemaValue(schema, "$")
	result, ok := cleaned.(map[string]any)
	if !ok {
		return nil
	}

	// 确保有 type 字段（默认 OBJECT）
	if _, hasType := result["type"]; !hasType {
		result["type"] = "OBJECT"
	}

	// 确保有 properties 字段（默认空对象）
	if _, hasProps := result["properties"]; !hasProps {
		result["properties"] = make(map[string]any)
	}

	// 验证 required 中的字段都存在于 properties 中
	if required, ok := result["required"].([]any); ok {
		if props, ok := result["properties"].(map[string]any); ok {
			validRequired := make([]any, 0, len(required))
			for _, r := range required {
				if reqName, ok := r.(string); ok {
					if _, exists := props[reqName]; exists {
						validRequired = append(validRequired, r)
					}
				}
			}
			if len(validRequired) > 0 {
				result["required"] = validRequired
			} else {
				delete(result, "required")
			}
		}
	}

	return result
}

var schemaValidationKeys = map[string]bool{
	"minLength":         true,
	"maxLength":         true,
	"pattern":           true,
	"minimum":           true,
	"maximum":           true,
	"exclusiveMinimum":  true,
	"exclusiveMaximum":  true,
	"multipleOf":        true,
	"uniqueItems":       true,
	"minItems":          true,
	"maxItems":          true,
	"minProperties":     true,
	"maxProperties":     true,
	"patternProperties": true,
	"propertyNames":     true,
	"dependencies":      true,
	"dependentSchemas":  true,
	"dependentRequired": true,
}

var warnedSchemaKeys sync.Map

func schemaCleaningWarningsEnabled() bool {
	// 可通过环境变量强制开关，方便排查：SUB2API_SCHEMA_CLEAN_WARN=true/false
	if v := strings.TrimSpace(os.Getenv("SUB2API_SCHEMA_CLEAN_WARN")); v != "" {
		switch strings.ToLower(v) {
		case "1", "true", "yes", "on":
			return true
		case "0", "false", "no", "off":
			return false
		}
	}
	// 默认：非 release 模式下输出（debug/test）
	return gin.Mode() != gin.ReleaseMode
}

func warnSchemaKeyRemovedOnce(key, path string) {
	if !schemaCleaningWarningsEnabled() {
		return
	}
	if !schemaValidationKeys[key] {
		return
	}
	if _, loaded := warnedSchemaKeys.LoadOrStore(key, struct{}{}); loaded {
		return
	}
	log.Printf("[SchemaClean] removed unsupported JSON Schema validation field key=%q path=%q", key, path)
}

// excludedSchemaKeys 不支持的 schema 字段
// 基于 Claude API (Vertex AI) 的实际支持情况
// 支持: type, description, enum, properties, required, additionalProperties, items
// 不支持: minItems, maxItems, minLength, maxLength, pattern, minimum, maximum 等验证字段
var excludedSchemaKeys = map[string]bool{
	// 元 schema 字段
	"$schema": true,
	"$id":     true,
	"$ref":    true,

	// 字符串验证（Gemini 不支持）
	"minLength": true,
	"maxLength": true,
	"pattern":   true,

	// 数字验证（Claude API 通过 Vertex AI 不支持这些字段）
	"minimum":          true,
	"maximum":          true,
	"exclusiveMinimum": true,
	"exclusiveMaximum": true,
	"multipleOf":       true,

	// 数组验证（Claude API 通过 Vertex AI 不支持这些字段）
	"uniqueItems": true,
	"minItems":    true,
	"maxItems":    true,

	// 组合 schema（Gemini 不支持）
	"oneOf":       true,
	"anyOf":       true,
	"allOf":       true,
	"not":         true,
	"if":          true,
	"then":        true,
	"else":        true,
	"$defs":       true,
	"definitions": true,

	// 对象验证（仅保留 properties/required/additionalProperties）
	"minProperties":     true,
	"maxProperties":     true,
	"patternProperties": true,
	"propertyNames":     true,
	"dependencies":      true,
	"dependentSchemas":  true,
	"dependentRequired": true,

	// 其他不支持的字段
	"default":          true,
	"const":            true,
	"examples":         true,
	"deprecated":       true,
	"readOnly":         true,
	"writeOnly":        true,
	"contentMediaType": true,
	"contentEncoding":  true,

	// Claude 特有字段
	"strict": true,
}

// cleanSchemaValue 递归清理 schema 值
func cleanSchemaValue(value any, path string) any {
	switch v := value.(type) {
	case map[string]any:
		result := make(map[string]any)
		for k, val := range v {
			// 跳过不支持的字段
			if excludedSchemaKeys[k] {
				warnSchemaKeyRemovedOnce(k, path)
				continue
			}

			// 特殊处理 type 字段
			if k == "type" {
				result[k] = cleanTypeValue(val)
				continue
			}

			// 特殊处理 format 字段：只保留 Gemini 支持的 format 值
			if k == "format" {
				if formatStr, ok := val.(string); ok {
					// Gemini 只支持 date-time, date, time
					if formatStr == "date-time" || formatStr == "date" || formatStr == "time" {
						result[k] = val
					}
					// 其他 format 值直接跳过
				}
				continue
			}

			// 特殊处理 additionalProperties：Claude API 只支持布尔值，不支持 schema 对象
			if k == "additionalProperties" {
				if boolVal, ok := val.(bool); ok {
					result[k] = boolVal
				} else {
					// 如果是 schema 对象，转换为 false（更安全的默认值）
					result[k] = false
				}
				continue
			}

			// 递归清理所有值
			result[k] = cleanSchemaValue(val, path+"."+k)
		}
		return result

	case []any:
		// 递归处理数组中的每个元素
		cleaned := make([]any, 0, len(v))
		for i, item := range v {
			cleaned = append(cleaned, cleanSchemaValue(item, fmt.Sprintf("%s[%d]", path, i)))
		}
		return cleaned

	default:
		return value
	}
}

// cleanTypeValue 处理 type 字段，转换为大写
func cleanTypeValue(value any) any {
	switch v := value.(type) {
	case string:
		return strings.ToUpper(v)
	case []any:
		// 联合类型 ["string", "null"] -> 取第一个非 null 类型
		for _, t := range v {
			if ts, ok := t.(string); ok && ts != "null" {
				return strings.ToUpper(ts)
			}
		}
		// 如果只有 null，返回 STRING
		return "STRING"
	default:
		return value
	}
}
