package conversion

import "nex/backend/internal/conversion/canonical"

// StreamDecoder 流式解码器接口
type StreamDecoder interface {
	ProcessChunk(rawChunk []byte) []canonical.CanonicalStreamEvent
	Flush() []canonical.CanonicalStreamEvent
}

// StreamEncoder 流式编码器接口
type StreamEncoder interface {
	EncodeEvent(event canonical.CanonicalStreamEvent) [][]byte
	Flush() [][]byte
}

// StreamConverter 流式转换器接口
type StreamConverter interface {
	ProcessChunk(rawChunk []byte) [][]byte
	Flush() [][]byte
}

// PassthroughStreamConverter 同协议透传流式转换器
type PassthroughStreamConverter struct{}

// NewPassthroughStreamConverter 创建透传流式转换器
func NewPassthroughStreamConverter() *PassthroughStreamConverter {
	return &PassthroughStreamConverter{}
}

// ProcessChunk 直接传递原始字节
func (c *PassthroughStreamConverter) ProcessChunk(rawChunk []byte) [][]byte {
	return [][]byte{rawChunk}
}

// Flush 无缓冲数据
func (c *PassthroughStreamConverter) Flush() [][]byte {
	return nil
}

// SmartPassthroughStreamConverter 同协议 Smart Passthrough 流式转换器
// 逐 chunk 改写 model 字段
type SmartPassthroughStreamConverter struct {
	adapter       ProtocolAdapter
	modelOverride string
	interfaceType InterfaceType
}

// NewSmartPassthroughStreamConverter 创建 Smart Passthrough 流式转换器
func NewSmartPassthroughStreamConverter(adapter ProtocolAdapter, modelOverride string, interfaceType InterfaceType) *SmartPassthroughStreamConverter {
	return &SmartPassthroughStreamConverter{
		adapter:       adapter,
		modelOverride: modelOverride,
		interfaceType: interfaceType,
	}
}

// ProcessChunk 改写 chunk 中的 model 字段
func (c *SmartPassthroughStreamConverter) ProcessChunk(rawChunk []byte) [][]byte {
	if len(rawChunk) == 0 {
		return nil
	}

	rewrittenChunk, err := c.adapter.RewriteResponseModelName(rawChunk, c.modelOverride, c.interfaceType)
	if err != nil {
		// 改写失败，返回原始 chunk
		return [][]byte{rawChunk}
	}

	return [][]byte{rewrittenChunk}
}

// Flush 无缓冲数据
func (c *SmartPassthroughStreamConverter) Flush() [][]byte {
	return nil
}

// CanonicalStreamConverter 跨协议规范流式转换器
type CanonicalStreamConverter struct {
	decoder          StreamDecoder
	encoder          StreamEncoder
	chain            *MiddlewareChain
	ctx              ConversionContext
	clientProtocol   string
	providerProtocol string
	modelOverride    string
}

// NewCanonicalStreamConverter 创建规范流式转换器
func NewCanonicalStreamConverter(decoder StreamDecoder, encoder StreamEncoder) *CanonicalStreamConverter {
	return &CanonicalStreamConverter{
		decoder: decoder,
		encoder: encoder,
	}
}

// NewCanonicalStreamConverterWithMiddleware 创建带中间件的规范流式转换器
func NewCanonicalStreamConverterWithMiddleware(decoder StreamDecoder, encoder StreamEncoder, chain *MiddlewareChain, ctx ConversionContext, clientProtocol, providerProtocol, modelOverride string) *CanonicalStreamConverter {
	return &CanonicalStreamConverter{
		decoder:          decoder,
		encoder:          encoder,
		chain:            chain,
		ctx:              ctx,
		clientProtocol:   clientProtocol,
		providerProtocol: providerProtocol,
		modelOverride:    modelOverride,
	}
}

// ProcessChunk 解码 → 中间件 → modelOverride → 编码管道
func (c *CanonicalStreamConverter) ProcessChunk(rawChunk []byte) [][]byte {
	events := c.decoder.ProcessChunk(rawChunk)
	var result [][]byte
	for i := range events {
		if c.chain != nil {
			processed, err := c.chain.ApplyStreamEvent(&events[i], c.clientProtocol, c.providerProtocol, &c.ctx)
			if err != nil {
				continue
			}
			events[i] = *processed
		}
		c.applyModelOverride(&events[i])
		chunks := c.encoder.EncodeEvent(events[i])
		result = append(result, chunks...)
	}
	return result
}

// Flush 刷新解码器和编码器缓冲区
func (c *CanonicalStreamConverter) Flush() [][]byte {
	events := c.decoder.Flush()
	var result [][]byte
	for i := range events {
		if c.chain != nil {
			processed, err := c.chain.ApplyStreamEvent(&events[i], c.clientProtocol, c.providerProtocol, &c.ctx)
			if err != nil {
				continue
			}
			events[i] = *processed
		}
		c.applyModelOverride(&events[i])
		chunks := c.encoder.EncodeEvent(events[i])
		result = append(result, chunks...)
	}
	encoderChunks := c.encoder.Flush()
	result = append(result, encoderChunks...)
	return result
}

// applyModelOverride 在跨协议场景下覆写流式事件中的 Model 字段
func (c *CanonicalStreamConverter) applyModelOverride(event *canonical.CanonicalStreamEvent) {
	if c.modelOverride != "" && event.Message != nil {
		event.Message.Model = c.modelOverride
	}
}