package convert

import (
	"encoding/json"

	"openteam/server/internal/proxy/claude"
	"openteam/server/internal/proxy/openai"
	"openteam/server/internal/proxy/stream"
)

// Usage is the streaming token usage snapshot.
type Usage struct {
	Input         int64
	Output        int64
	CacheRead     int64
	CacheCreation int64
}

// Translator converts SSE events from an upstream stream into client frames.
type Translator interface {
	// Feed handles one upstream SSE event, returning client frames to write.
	Feed(ev stream.SSEEvent) ([]stream.SSEEvent, error)
	// Finish is called at end-of-stream, returning final frames.
	Finish() ([]stream.SSEEvent, error)
	// Usage returns the latest known usage.
	Usage() *Usage
}

// claudeToChatTranslator converts a Claude stream to OpenAI chat chunks.
type claudeToChatTranslator struct {
	model          string
	usage          *Usage
	started        bool
	finishSent     bool
	toolCallIndex  int
	toolCallID     string
	toolCallName   string
}

func (t *claudeToChatTranslator) Feed(ev stream.SSEEvent) ([]stream.SSEEvent, error) {
	if ev.Done {
		return nil, nil
	}
	var e claude.StreamEvent
	if err := json.Unmarshal([]byte(ev.Data), &e); err != nil {
		return nil, nil
	}
	var out []stream.SSEEvent

	switch e.Type {
	case "message_start":
		if e.Message != nil {
			var msg struct {
				Model string `json:"model"`
			}
			_ = json.Unmarshal(e.Message, &msg)
			t.model = msg.Model
		}
		chunk, _ := json.Marshal(openai.ChatChunk{
			ID: "chatcmpl-stream", Object: "chat.completion.chunk", Model: t.model,
			Choices: []openai.ChatChunkChoice{{Index: 0, Delta: openai.ChatDelta{Role: "assistant"}}},
		})
		out = append(out, stream.SSEEvent{Data: string(chunk)})
		t.started = true

	case "content_block_start":
		var cb struct {
			Index int             `json:"index"`
			Block json.RawMessage `json:"content_block"`
		}
		_ = json.Unmarshal([]byte(ev.Data), &cb)
		var block struct {
			Type  string `json:"type"`
			ID    string `json:"id"`
			Name  string `json:"name"`
		}
		_ = json.Unmarshal(cb.Block, &block)
		if block.Type == "tool_use" {
			t.toolCallIndex = cb.Index
			t.toolCallID = block.ID
			t.toolCallName = block.Name
			tc, _ := json.Marshal([]map[string]any{{
				"index": cb.Index, "id": block.ID, "type": "function",
				"function": map[string]any{"name": block.Name, "arguments": ""},
			}})
			chunk, _ := json.Marshal(openai.ChatChunk{
				ID: "chatcmpl-stream", Object: "chat.completion.chunk", Model: t.model,
				Choices: []openai.ChatChunkChoice{{Index: 0, Delta: openai.ChatDelta{ToolCalls: tc}}},
			})
			out = append(out, stream.SSEEvent{Data: string(chunk)})
		}

	case "content_block_delta":
		var d struct {
			Index int             `json:"index"`
			Delta json.RawMessage `json:"delta"`
		}
		_ = json.Unmarshal([]byte(ev.Data), &d)
		var delta struct {
			Type string `json:"type"`
			Text string `json:"text"`
			PartialJSON string `json:"partial_json"`
		}
		_ = json.Unmarshal(d.Delta, &delta)
		if delta.Type == "text_delta" && delta.Text != "" {
			chunk, _ := json.Marshal(openai.ChatChunk{
				ID: "chatcmpl-stream", Object: "chat.completion.chunk", Model: t.model,
				Choices: []openai.ChatChunkChoice{{Index: 0, Delta: openai.ChatDelta{Content: delta.Text}}},
			})
			out = append(out, stream.SSEEvent{Data: string(chunk)})
		} else if delta.Type == "input_json_delta" && delta.PartialJSON != "" {
			tc, _ := json.Marshal([]map[string]any{{
				"index": d.Index, "function": map[string]any{"arguments": delta.PartialJSON},
			}})
			chunk, _ := json.Marshal(openai.ChatChunk{
				ID: "chatcmpl-stream", Object: "chat.completion.chunk", Model: t.model,
				Choices: []openai.ChatChunkChoice{{Index: 0, Delta: openai.ChatDelta{ToolCalls: tc}}},
			})
			out = append(out, stream.SSEEvent{Data: string(chunk)})
		}

	case "message_delta":
		var d struct {
			Delta json.RawMessage `json:"delta"`
			Usage json.RawMessage `json:"usage"`
		}
		_ = json.Unmarshal([]byte(ev.Data), &d)
		if len(d.Usage) > 0 {
			var u claude.Usage
			if json.Unmarshal(d.Usage, &u) == nil {
				t.usage = &Usage{
					Input: u.InputTokens, Output: u.OutputTokens,
					CacheRead: u.CacheReadInputTokens, CacheCreation: u.CacheCreationInputTokens,
				}
			}
		}
		if len(d.Delta) > 0 && !t.finishSent {
			var delta struct {
				StopReason string `json:"stop_reason"`
			}
			_ = json.Unmarshal(d.Delta, &delta)
			if delta.StopReason != "" {
				reason := mapClaudeStopReason(delta.StopReason)
				chunk, _ := json.Marshal(openai.ChatChunk{
					ID: "chatcmpl-stream", Object: "chat.completion.chunk", Model: t.model,
					Choices: []openai.ChatChunkChoice{{Index: 0, Delta: openai.ChatDelta{}, FinishReason: &reason}},
				})
				out = append(out, stream.SSEEvent{Data: string(chunk)})
				t.finishSent = true
			}
		}
	}
	return out, nil
}

func (t *claudeToChatTranslator) Finish() ([]stream.SSEEvent, error) {
	if !t.finishSent {
		reason := "stop"
		chunk, _ := json.Marshal(openai.ChatChunk{
			ID: "chatcmpl-stream", Object: "chat.completion.chunk", Model: t.model,
			Choices: []openai.ChatChunkChoice{{Index: 0, Delta: openai.ChatDelta{}, FinishReason: &reason}},
		})
		t.finishSent = true
		return []stream.SSEEvent{{Data: string(chunk)}, {Data: "[DONE]"}}, nil
	}
	return []stream.SSEEvent{{Data: "[DONE]"}}, nil
}

func (t *claudeToChatTranslator) Usage() *Usage { return t.usage }

// chatToClaudeTranslator converts an OpenAI chat stream to Claude events.
type chatToClaudeTranslator struct {
	usage          *Usage
	started        bool
	openBlock      bool
	blockType      string
	toolIndex      int
	finishSent     bool
}

func (t *chatToClaudeTranslator) Feed(ev stream.SSEEvent) ([]stream.SSEEvent, error) {
	if ev.Done {
		return nil, nil
	}
	var chunk openai.ChatChunk
	if err := json.Unmarshal([]byte(ev.Data), &chunk); err != nil {
		return nil, nil
	}
	if chunk.Usage != nil {
		t.usage = &Usage{Input: chunk.Usage.PromptTokens, Output: chunk.Usage.CompletionTokens}
	}
	var out []stream.SSEEvent
	if len(chunk.Choices) == 0 {
		return out, nil
	}
	ch := chunk.Choices[0]

	if !t.started {
		msg, _ := json.Marshal(map[string]any{
			"id": "msg_stream", "type": "message", "role": "assistant",
			"model": chunk.Model, "content": []any{},
		})
		start, _ := json.Marshal(map[string]any{"type": "message_start", "message": json.RawMessage(msg)})
		out = append(out, stream.SSEEvent{Data: string(start)})
		t.started = true
	}

	if ch.Delta.Content != "" {
		if !t.openBlock || t.blockType != "text" {
			start, _ := json.Marshal(map[string]any{
				"type": "content_block_start", "index": 0,
				"content_block": map[string]any{"type": "text", "text": ""},
			})
			out = append(out, stream.SSEEvent{Data: string(start)})
			t.openBlock = true
			t.blockType = "text"
			t.toolIndex = 0
		}
		delta, _ := json.Marshal(map[string]any{
			"type": "content_block_delta", "index": 0,
			"delta": map[string]any{"type": "text_delta", "text": ch.Delta.Content},
		})
		out = append(out, stream.SSEEvent{Data: string(delta)})
	}

	if len(ch.Delta.ToolCalls) > 0 {
		var calls []struct {
			Index    *int   `json:"index"`
			ID       string `json:"id"`
			Function struct {
				Name      string `json:"name"`
				Arguments string `json:"arguments"`
			} `json:"function"`
		}
		_ = json.Unmarshal(ch.Delta.ToolCalls, &calls)
		for _, call := range calls {
			idx := 0
			if call.Index != nil {
				idx = *call.Index
			}
			if !t.openBlock || t.blockType != "tool_use" || idx != t.toolIndex {
				start, _ := json.Marshal(map[string]any{
					"type": "content_block_start", "index": idx,
					"content_block": map[string]any{
						"type": "tool_use", "id": call.ID, "name": call.Function.Name, "input": map[string]any{},
					},
				})
				out = append(out, stream.SSEEvent{Data: string(start)})
				t.openBlock = true
				t.blockType = "tool_use"
				t.toolIndex = idx
			}
			if call.Function.Arguments != "" {
				delta, _ := json.Marshal(map[string]any{
					"type": "content_block_delta", "index": idx,
					"delta": map[string]any{"type": "input_json_delta", "partial_json": call.Function.Arguments},
				})
				out = append(out, stream.SSEEvent{Data: string(delta)})
			}
		}
	}

	if ch.FinishReason != nil && !t.finishSent {
		reason := mapChatStopReasonToClaude(*ch.FinishReason)
		md, _ := json.Marshal(map[string]any{
			"type": "message_delta",
			"delta": map[string]any{"stop_reason": reason, "stop_sequence": nil},
		})
		out = append(out, stream.SSEEvent{Data: string(md)})
		t.finishSent = true
	}
	return out, nil
}

func (t *chatToClaudeTranslator) Finish() ([]stream.SSEEvent, error) {
	if !t.finishSent {
		md, _ := json.Marshal(map[string]any{
			"type": "message_delta",
			"delta": map[string]any{"stop_reason": "end_turn", "stop_sequence": nil},
		})
		t.finishSent = true
		return []stream.SSEEvent{{Data: string(md)}, {Data: "{\"type\":\"message_stop\"}"}}, nil
	}
	return []stream.SSEEvent{{Data: "{\"type\":\"message_stop\"}"}}, nil
}

func (t *chatToClaudeTranslator) Usage() *Usage { return t.usage }

// claudeToResponsesTranslator converts a Claude stream to Responses events.
type claudeToResponsesTranslator struct {
	usage      *Usage
	model      string
	completed  bool
}

func (t *claudeToResponsesTranslator) Feed(ev stream.SSEEvent) ([]stream.SSEEvent, error) {
	if ev.Done {
		return nil, nil
	}
	var e claude.StreamEvent
	if err := json.Unmarshal([]byte(ev.Data), &e); err != nil {
		return nil, nil
	}
	var out []stream.SSEEvent
	switch e.Type {
	case "message_start":
		if e.Message != nil {
			var msg struct {
				Model string `json:"model"`
			}
			_ = json.Unmarshal(e.Message, &msg)
			t.model = msg.Model
		}
		created, _ := json.Marshal(map[string]any{
			"type": "response.created",
			"response": map[string]any{"id": "resp_stream", "object": "response", "status": "in_progress", "model": t.model, "output": []any{}},
		})
		out = append(out, stream.SSEEvent{Data: string(created)})
	case "content_block_delta":
		var d struct {
			Index int             `json:"index"`
			Delta json.RawMessage `json:"delta"`
		}
		_ = json.Unmarshal([]byte(ev.Data), &d)
		var delta struct {
			Type string `json:"type"`
			Text string `json:"text"`
		}
		_ = json.Unmarshal(d.Delta, &delta)
		if delta.Type == "text_delta" && delta.Text != "" {
			item, _ := json.Marshal(map[string]any{
				"type": "response.output_text.delta", "item_id": "msg_stream", "output_index": 0,
				"delta": delta.Text,
			})
			out = append(out, stream.SSEEvent{Data: string(item)})
		}
	case "message_delta":
		var d struct {
			Usage json.RawMessage `json:"usage"`
		}
		_ = json.Unmarshal([]byte(ev.Data), &d)
		if len(d.Usage) > 0 {
			var u claude.Usage
			if json.Unmarshal(d.Usage, &u) == nil {
				t.usage = &Usage{
					Input: u.InputTokens, Output: u.OutputTokens,
					CacheRead: u.CacheReadInputTokens, CacheCreation: u.CacheCreationInputTokens,
				}
			}
		}
		if !t.completed {
			item, _ := json.Marshal(map[string]any{
				"type": "response.completed",
				"response": map[string]any{
					"id": "resp_stream", "object": "response", "status": "completed", "model": t.model,
					"output": []map[string]any{{"type": "message", "role": "assistant", "content": []any{}}},
				},
			})
			out = append(out, stream.SSEEvent{Data: string(item)})
			t.completed = true
		}
	}
	return out, nil
}

func (t *claudeToResponsesTranslator) Finish() ([]stream.SSEEvent, error) {
	if !t.completed {
		item, _ := json.Marshal(map[string]any{
			"type": "response.completed",
			"response": map[string]any{
				"id": "resp_stream", "object": "response", "status": "completed", "model": t.model,
				"output": []map[string]any{{"type": "message", "role": "assistant", "content": []any{}}},
			},
		})
		t.completed = true
		return []stream.SSEEvent{{Data: string(item)}, {Data: "[DONE]"}}, nil
	}
	return []stream.SSEEvent{{Data: "[DONE]"}}, nil
}

func (t *claudeToResponsesTranslator) Usage() *Usage { return t.usage }

func mapChatStopReasonToClaude(reason string) string {
	switch reason {
	case "stop":
		return "end_turn"
	case "length":
		return "max_tokens"
	case "tool_calls":
		return "tool_use"
	case "content_filter":
		return "refusal"
	default:
		return "end_turn"
	}
}

// NewTranslator returns the stream translator for a client protocol +
// upstream provider pair, or nil for passthrough (no translation needed).
func NewTranslator(client ClientProtocol, provider string) Translator {
	switch client {
	case ClientOpenAIChat:
		if provider == "anthropic" {
			return &claudeToChatTranslator{}
		}
	case ClientOpenAIResponses:
		if provider == "anthropic" {
			return &claudeToResponsesTranslator{}
		}
	case ClientAnthropic:
		if provider == "openai" || provider == "compatible" {
			return &chatToClaudeTranslator{}
		}
	}
	return nil
}