package service

import (
	"encoding/json"
	"fmt"
	"strings"

	"oci-portal/internal/aiwire"
)

// ResponsesToIR 把 Responses API 请求转换为网关 IR(OpenAI Chat 形态)。
// 有状态特性与内置工具不支持,直接报错(API 层 400)。
func ResponsesToIR(req aiwire.RespRequest) (aiwire.ChatRequest, error) {
	if err := respRejectUnsupported(req); err != nil {
		return aiwire.ChatRequest{}, err
	}
	ir := aiwire.ChatRequest{
		Model:       req.Model,
		MaxTokens:   req.MaxOutputTokens,
		Temperature: req.Temperature,
		TopP:        req.TopP,
		Stream:      req.Stream,
		ToolChoice:  respToolChoice(req.ToolChoice),
	}
	if req.Reasoning != nil {
		ir.ReasoningEffort = req.Reasoning.Effort
	}
	if req.Instructions != "" {
		ir.Messages = append(ir.Messages, aiwire.ChatMessage{Role: "system", Content: aiwire.NewTextContent(req.Instructions)})
	}
	msgs, err := respInputToMessages(req.Input)
	if err != nil {
		return aiwire.ChatRequest{}, err
	}
	ir.Messages = append(ir.Messages, msgs...)
	ir.Tools = respTools(req.Tools)
	ir.ResponseFormat = respFormat(req.Text)
	return ir, nil
}

// respRejectUnsupported 拒绝无状态网关无法承接的请求特性。
func respRejectUnsupported(req aiwire.RespRequest) error {
	if req.PreviousResponseID != "" {
		return fmt.Errorf("previous_response_id 不支持:网关不保存历史响应,请在 input 中自带完整上下文(store:false 模式)")
	}
	if len(req.Conversation) > 0 && string(req.Conversation) != "null" {
		return fmt.Errorf("conversation 不支持:网关不保存对话状态")
	}
	if req.Background != nil && *req.Background {
		return fmt.Errorf("background 模式不支持")
	}
	for _, t := range req.Tools {
		if t.Type != "function" {
			return fmt.Errorf("不支持的工具类型 %q:仅支持 function 工具", t.Type)
		}
	}
	return nil
}

// respInputToMessages 把 input(string 或 item 数组)展开为 IR 消息序列。
func respInputToMessages(in aiwire.RespInput) ([]aiwire.ChatMessage, error) {
	if !in.IsArray {
		if strings.TrimSpace(in.Text) == "" {
			return nil, fmt.Errorf("input 不能为空")
		}
		return []aiwire.ChatMessage{{Role: "user", Content: aiwire.NewTextContent(in.Text)}}, nil
	}
	var msgs []aiwire.ChatMessage
	for _, it := range in.Items {
		out, err := respItemToMessages(it, msgs)
		if err != nil {
			return nil, err
		}
		msgs = out
	}
	return msgs, nil
}

// respItemToMessages 追加一个 input item;连续 function_call 合并进同一 assistant 消息。
func respItemToMessages(it aiwire.RespItem, msgs []aiwire.ChatMessage) ([]aiwire.ChatMessage, error) {
	switch it.Type {
	case "", "message":
		if it.Content.HasUnsupported() {
			return nil, ErrAiUnsupportedBlock
		}
		role := respRole(it.Role)
		return append(msgs, aiwire.ChatMessage{Role: role, Content: respContentToIR(it.Content)}), nil
	case "function_call":
		call := aiwire.ToolCall{ID: it.CallID, Type: "function",
			Function: aiwire.FunctionCall{Name: it.Name, Arguments: it.Arguments}}
		if n := len(msgs); n > 0 && msgs[n-1].Role == "assistant" && len(msgs[n-1].ToolCalls) > 0 {
			msgs[n-1].ToolCalls = append(msgs[n-1].ToolCalls, call)
			return msgs, nil
		}
		return append(msgs, aiwire.ChatMessage{Role: "assistant", ToolCalls: []aiwire.ToolCall{call}}), nil
	case "function_call_output":
		return append(msgs, aiwire.ChatMessage{Role: "tool", ToolCallID: it.CallID,
			Content: aiwire.NewTextContent(it.OutputText())}), nil
	case "reasoning":
		return msgs, nil // 推理块不回灌上游
	default:
		return nil, fmt.Errorf("不支持的 input item 类型 %q", it.Type)
	}
}

// respRole 归一 item 角色;developer 视为 system,缺省 user。
func respRole(role string) string {
	switch role {
	case "system", "developer":
		return "system"
	case "assistant":
		return "assistant"
	default:
		return "user"
	}
}

// respContentToIR 把 Responses 内容转 IR;纯文本拍平,含图片时保留部件顺序。
func respContentToIR(c aiwire.RespContent) aiwire.Content {
	var parts []aiwire.ContentPart
	hasImage := false
	for _, p := range c.Parts {
		switch p.Type {
		case "input_image":
			parts = append(parts, aiwire.ContentPart{Type: "image_url",
				ImageURL: &aiwire.ImageURL{URL: p.ImageURL, Detail: p.Detail}})
			hasImage = true
		default:
			if p.Text != "" {
				parts = append(parts, aiwire.ContentPart{Type: "text", Text: p.Text})
			}
		}
	}
	if !c.IsArray || !hasImage {
		return aiwire.NewTextContent(c.JoinText())
	}
	return aiwire.NewPartsContent(parts)
}

// respTools 把扁平工具定义还原为嵌套 Chat 形态;strict 无 OCI 对应,忽略。
func respTools(tools []aiwire.RespTool) []aiwire.Tool {
	if len(tools) == 0 {
		return nil
	}
	out := make([]aiwire.Tool, 0, len(tools))
	for _, t := range tools {
		out = append(out, aiwire.Tool{Type: "function",
			Function: aiwire.FunctionDef{Name: t.Name, Description: t.Description, Parameters: t.Parameters}})
	}
	return out
}

// respToolChoice 转换 tool_choice:字符串直通;{type:function,name} 转嵌套;
// allowed_tools 等对象形态降级 auto。
func respToolChoice(raw json.RawMessage) json.RawMessage {
	if len(raw) == 0 {
		return nil
	}
	t := strings.TrimSpace(string(raw))
	if strings.HasPrefix(t, "\"") {
		return raw
	}
	var obj struct {
		Type string `json:"type"`
		Name string `json:"name"`
	}
	if err := json.Unmarshal(raw, &obj); err != nil || obj.Type != "function" || obj.Name == "" {
		return json.RawMessage(`"auto"`)
	}
	out, _ := json.Marshal(map[string]any{"type": "function", "function": map[string]string{"name": obj.Name}})
	return out
}

// respFormat 把 text.format 转成 response_format;text 形态无需显式指定。
func respFormat(text *aiwire.RespText) *aiwire.ResponseFormat {
	if text == nil || text.Format == nil {
		return nil
	}
	switch text.Format.Type {
	case "json_object":
		return &aiwire.ResponseFormat{Type: "json_object"}
	case "json_schema":
		spec, _ := json.Marshal(map[string]any{
			"name": text.Format.Name, "schema": json.RawMessage(text.Format.Schema), "strict": text.Format.Strict,
		})
		return &aiwire.ResponseFormat{Type: "json_schema", JSONSchema: spec}
	default:
		return nil
	}
}

// IRRespToResponses 把 IR 非流式响应装配为 Response 对象。
func IRRespToResponses(resp *aiwire.ChatResponse, id string, created int64) aiwire.Response {
	out := aiwire.Response{ID: id, Object: "response", CreatedAt: created,
		Status: "completed", Model: resp.Model, Output: []aiwire.RespOutItem{}, Store: false}
	if len(resp.Choices) == 0 {
		return out
	}
	choice := resp.Choices[0]
	if text := choice.Message.Content.JoinText(); text != "" {
		out.Output = append(out.Output, respMessageItem(id, 0, text))
	}
	for i, tc := range choice.Message.ToolCalls {
		out.Output = append(out.Output, aiwire.RespOutItem{Type: "function_call",
			ID: respItemID(id, "fc", len(out.Output)+i), Status: "completed",
			CallID: tc.ID, Name: tc.Function.Name, Arguments: respArgs(tc.Function.Arguments)})
	}
	if choice.FinishReason == "length" {
		out.Status = "incomplete"
		out.IncompleteDetails = &aiwire.RespIncomplete{Reason: "max_output_tokens"}
	}
	out.Usage = respUsage(resp.Usage)
	return out
}

func respMessageItem(respID string, idx int, text string) aiwire.RespOutItem {
	return aiwire.RespOutItem{Type: "message", ID: respItemID(respID, "msg", idx),
		Status: "completed", Role: "assistant",
		Content: []aiwire.RespOutPart{{Type: "output_text", Text: text, Annotations: []any{}}}}
}

// respItemID 从响应 ID 派生确定性 item ID。
func respItemID(respID, kind string, idx int) string {
	return fmt.Sprintf("%s_%s_%d", kind, strings.TrimPrefix(respID, "resp_"), idx)
}

// respArgs 保证 arguments 是合法 JSON 字符串(空实参回退 {})。
func respArgs(args string) string {
	if strings.TrimSpace(args) == "" {
		return "{}"
	}
	return args
}

// respUsage 把 IR 用量改写为 Responses 命名口径。
func respUsage(u *aiwire.Usage) *aiwire.RespUsage {
	if u == nil {
		return nil
	}
	return &aiwire.RespUsage{InputTokens: u.PromptTokens, OutputTokens: u.CompletionTokens,
		TotalTokens:        u.TotalTokens,
		InputTokensDetails: aiwire.RespInDetails{CachedTokens: u.CachedTokens()}}
}