Add Azure OpenAI provider

internal/config/config.go

@@ -28,9 +28,10 @@ type ServerConfig struct {
 
 // ProvidersConfig wraps supported provider settings.
 type ProvidersConfig struct {
-	Google    ProviderConfig `yaml:"google"`
-	Anthropic ProviderConfig `yaml:"anthropic"`
-	OpenAI    ProviderConfig `yaml:"openai"`
+	Google       ProviderConfig       `yaml:"google"`
+	Anthropic    ProviderConfig       `yaml:"anthropic"`
+	OpenAI       ProviderConfig       `yaml:"openai"`
+	AzureOpenAI  AzureOpenAIConfig    `yaml:"azureopenai"`
 }
 
 // ProviderConfig contains shared provider configuration fields.
@@ -40,6 +41,14 @@ type ProviderConfig struct {
 	Endpoint string `yaml:"endpoint"`
 }
 
+// AzureOpenAIConfig contains Azure-specific settings.
+type AzureOpenAIConfig struct {
+	APIKey       string `yaml:"api_key"`
+	Endpoint     string `yaml:"endpoint"`
+	DeploymentID string `yaml:"deployment_id"`
+	APIVersion   string `yaml:"api_version"`
+}
+
 // Load reads and parses a YAML configuration file and applies env overrides.
 func Load(path string) (*Config, error) {
 	data, err := os.ReadFile(path)
@@ -60,6 +69,20 @@ func (cfg *Config) applyEnvOverrides() {
 	overrideAPIKey(&cfg.Providers.Google, "GOOGLE_API_KEY")
 	overrideAPIKey(&cfg.Providers.Anthropic, "ANTHROPIC_API_KEY")
 	overrideAPIKey(&cfg.Providers.OpenAI, "OPENAI_API_KEY")
+	
+	// Azure OpenAI overrides
+	if v := os.Getenv("AZURE_OPENAI_API_KEY"); v != "" {
+		cfg.Providers.AzureOpenAI.APIKey = v
+	}
+	if v := os.Getenv("AZURE_OPENAI_ENDPOINT"); v != "" {
+		cfg.Providers.AzureOpenAI.Endpoint = v
+	}
+	if v := os.Getenv("AZURE_OPENAI_DEPLOYMENT_ID"); v != "" {
+		cfg.Providers.AzureOpenAI.DeploymentID = v
+	}
+	if v := os.Getenv("AZURE_OPENAI_API_VERSION"); v != "" {
+		cfg.Providers.AzureOpenAI.APIVersion = v
+	}
 }
 
 func overrideAPIKey(cfg *ProviderConfig, envKey string) {

internal/providers/openai/openai.go

@@ -6,6 +6,7 @@ import (
 	"time"
 
 	"github.com/openai/openai-go"
+	"github.com/openai/openai-go/azure"
 	"github.com/openai/openai-go/option"
 
 	"github.com/yourusername/go-llm-gateway/internal/api"
@@ -15,12 +16,14 @@ import (
 const Name = "openai"
 
 // Provider implements the OpenAI SDK integration.
+// It supports both direct OpenAI API and Azure-hosted endpoints.
 type Provider struct {
 	cfg    config.ProviderConfig
 	client *openai.Client
+	azure  bool
 }
 
-// New constructs a Provider from configuration.
+// New constructs a Provider for the direct OpenAI API.
 func New(cfg config.ProviderConfig) *Provider {
 	var client *openai.Client
 	if cfg.APIKey != "" {
@@ -33,6 +36,32 @@ func New(cfg config.ProviderConfig) *Provider {
 	}
 }
 
+// NewAzure constructs a Provider targeting Azure OpenAI.
+// Azure OpenAI uses the OpenAI SDK with the azure subpackage for proper
+// endpoint routing, api-version query parameter, and API key header.
+func NewAzure(azureCfg config.AzureOpenAIConfig) *Provider {
+	var client *openai.Client
+	if azureCfg.APIKey != "" && azureCfg.Endpoint != "" {
+		apiVersion := azureCfg.APIVersion
+		if apiVersion == "" {
+			apiVersion = "2024-12-01-preview"
+		}
+		c := openai.NewClient(
+			azure.WithEndpoint(azureCfg.Endpoint, apiVersion),
+			azure.WithAPIKey(azureCfg.APIKey),
+		)
+		client = &c
+	}
+	return &Provider{
+		cfg: config.ProviderConfig{
+			APIKey: azureCfg.APIKey,
+			Model:  azureCfg.DeploymentID,
+		},
+		client: client,
+		azure:  true,
+	}
+}
+
 // Name returns the provider identifier.
 func (p *Provider) Name() string { return Name }
 

internal/providers/providers.go

@@ -34,7 +34,9 @@ func NewRegistry(cfg config.ProvidersConfig) (*Registry, error) {
 	if cfg.Anthropic.APIKey != "" {
 		reg.providers[anthropicprovider.Name] = anthropicprovider.New(cfg.Anthropic)
 	}
-	if cfg.OpenAI.APIKey != "" {
+	if cfg.AzureOpenAI.APIKey != "" && cfg.AzureOpenAI.Endpoint != "" {
+		reg.providers[openaiprovider.Name] = openaiprovider.NewAzure(cfg.AzureOpenAI)
+	} else if cfg.OpenAI.APIKey != "" {
 		reg.providers[openaiprovider.Name] = openaiprovider.New(cfg.OpenAI)
 	}
 
@@ -55,7 +57,7 @@ func (r *Registry) Get(name string) (Provider, bool) {
 func (r *Registry) Default(model string) (Provider, error) {
 	if model != "" {
 		switch {
-		case strings.HasPrefix(model, "gpt") || strings.HasPrefix(model, "o1"):
+		case strings.HasPrefix(model, "gpt") || strings.HasPrefix(model, "o1") || strings.HasPrefix(model, "o3"):
 			if p, ok := r.providers[openaiprovider.Name]; ok {
 				return p, nil
 			}