support ai proxy for cohere (#960) (#1328)

plugins/wasm-go/extensions/ai-proxy/README.md

@@ -215,6 +215,10 @@ DeepL 所对应的 `type` 为 `deepl`。它特有的配置字段如下：
 | ------------ | -------- | -------- | ------ | ---------------------------- |
 | `targetLang` | string   | 必填     | -      | DeepL 翻译服务需要的目标语种 |
 
+#### Cohere
+
+Cohere 所对应的 `type` 为 `cohere`。它并无特有的配置字段。
+
 ## 用法示例
 
 ### 使用 OpenAI 协议代理 Azure OpenAI 服务

plugins/wasm-go/extensions/ai-proxy/provider/cohere.go

@@ -0,0 +1,114 @@
+package provider
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+
+	"github.com/alibaba/higress/plugins/wasm-go/extensions/ai-proxy/util"
+	"github.com/alibaba/higress/plugins/wasm-go/pkg/wrapper"
+	"github.com/higress-group/proxy-wasm-go-sdk/proxywasm"
+	"github.com/higress-group/proxy-wasm-go-sdk/proxywasm/types"
+)
+
+const (
+	cohereDomain       = "api.cohere.com"
+	chatCompletionPath = "/v1/chat"
+)
+
+type cohereProviderInitializer struct{}
+
+func (m *cohereProviderInitializer) ValidateConfig(config ProviderConfig) error {
+	if config.apiTokens == nil || len(config.apiTokens) == 0 {
+		return errors.New("no apiToken found in provider config")
+	}
+	return nil
+}
+
+func (m *cohereProviderInitializer) CreateProvider(config ProviderConfig) (Provider, error) {
+	return &cohereProvider{
+		config: config,
+	}, nil
+}
+
+type cohereProvider struct {
+	config ProviderConfig
+}
+
+type cohereTextGenRequest struct {
+	Message          string   `json:"message,omitempty"`
+	Model            string   `json:"model,omitempty"`
+	Stream           bool     `json:"stream,omitempty"`
+	MaxTokens        int      `json:"max_tokens,omitempty"`
+	Temperature      float64  `json:"temperature,omitempty"`
+	K                int      `json:"k,omitempty"`
+	P                float64  `json:"p,omitempty"`
+	Seed             int      `json:"seed,omitempty"`
+	StopSequences    []string `json:"stop_sequences,omitempty"`
+	FrequencyPenalty float64  `json:"frequency_penalty,omitempty"`
+	PresencePenalty  float64  `json:"presence_penalty,omitempty"`
+}
+
+func (m *cohereProvider) GetProviderType() string {
+	return providerTypeCohere
+}
+
+func (m *cohereProvider) OnRequestHeaders(ctx wrapper.HttpContext, apiName ApiName, log wrapper.Log) (types.Action, error) {
+	if apiName != ApiNameChatCompletion {
+		return types.ActionContinue, errUnsupportedApiName
+	}
+	_ = util.OverwriteRequestHost(cohereDomain)
+	_ = util.OverwriteRequestPath(chatCompletionPath)
+	_ = util.OverwriteRequestAuthorization("Bearer " + m.config.GetRandomToken())
+	_ = proxywasm.RemoveHttpRequestHeader("Content-Length")
+	return types.ActionContinue, nil
+}
+
+func (m *cohereProvider) OnRequestBody(ctx wrapper.HttpContext, apiName ApiName, body []byte, log wrapper.Log) (types.Action, error) {
+	if apiName != ApiNameChatCompletion {
+		return types.ActionContinue, errUnsupportedApiName
+	}
+	if m.config.protocol == protocolOriginal {
+		request := &cohereTextGenRequest{}
+		if err := json.Unmarshal(body, request); err != nil {
+			return types.ActionContinue, fmt.Errorf("unable to unmarshal request: %v", err)
+		}
+		return m.handleRequestBody(log, request)
+	}
+	origin := &chatCompletionRequest{}
+	if err := decodeChatCompletionRequest(body, origin); err != nil {
+		return types.ActionContinue, err
+	}
+	request := m.buildCohereRequest(origin)
+	return m.handleRequestBody(log, request)
+}
+
+func (m *cohereProvider) handleRequestBody(log wrapper.Log, request interface{}) (types.Action, error) {
+	defer func() {
+		_ = proxywasm.ResumeHttpRequest()
+	}()
+	err := replaceJsonRequestBody(request, log)
+	if err != nil {
+		_ = util.SendResponse(500, "ai-proxy.cohere.proxy_failed", util.MimeTypeTextPlain, fmt.Sprintf("failed to replace request body: %v", err))
+	}
+	return types.ActionContinue, err
+}
+
+func (m *cohereProvider) buildCohereRequest(origin *chatCompletionRequest) *cohereTextGenRequest {
+	if len(origin.Messages) == 0 {
+		return nil
+	}
+	return &cohereTextGenRequest{
+		Message:          origin.Messages[0].StringContent(),
+		Model:            origin.Model,
+		MaxTokens:        origin.MaxTokens,
+		Stream:           origin.Stream,
+		Temperature:      origin.Temperature,
+		K:                origin.N,
+		P:                origin.TopP,
+		Seed:             origin.Seed,
+		StopSequences:    origin.Stop,
+		FrequencyPenalty: origin.FrequencyPenalty,
+		PresencePenalty:  origin.PresencePenalty,
+	}
+}

plugins/wasm-go/extensions/ai-proxy/provider/provider.go

@@ -38,6 +38,7 @@ const (
 	providerTypeGemini     = "gemini"
 	providerTypeDeepl      = "deepl"
 	providerTypeMistral    = "mistral"
+	providerTypeCohere     = "cohere"
 
 	protocolOpenAI   = "openai"
 	protocolOriginal = "original"
@@ -94,6 +95,7 @@ var (
 		providerTypeGemini:     &geminiProviderInitializer{},
 		providerTypeDeepl:      &deeplProviderInitializer{},
 		providerTypeMistral:    &mistralProviderInitializer{},
+		providerTypeCohere:     &cohereProviderInitializer{},
 	}
 )