Add Ollama SDK with Core Functionality and Documentation

- Introduced the Ollama SDK, providing a comprehensive interface for interacting with Ollama AI models, including text generation, chat conversations, embeddings, and model management.
- Implemented core components such as Client, Config, and various request/response entities to facilitate API interactions.
- Added structured error handling with specific error types for improved clarity and debugging.
- Included a README and usage guide to assist developers in integrating the SDK into their applications, ensuring a smooth onboarding experience.
- Established a fluent API for chat interactions and streaming responses, enhancing usability and flexibility for developers.

pkg/ollama/errors.go

@@ -0,0 +1,146 @@
+package ollama
+
+import (
+	"fmt"
+)
+
+// Error types for the Ollama SDK
+var (
+	// ErrInvalidConfig is returned when configuration is invalid
+	ErrInvalidConfig = func(msg string) error {
+		return &ConfigError{Message: msg}
+	}
+
+	// ErrInvalidRequest is returned when a request is invalid
+	ErrInvalidRequest = func(msg string) error {
+		return &RequestError{Message: msg}
+	}
+
+	// ErrModelNotFound is returned when a model is not found
+	ErrModelNotFound = func(model string) error {
+		return &ModelError{Message: fmt.Sprintf("model %s not found", model), Model: model}
+	}
+
+	// ErrModelPullFailed is returned when pulling a model fails
+	ErrModelPullFailed = func(model string, reason string) error {
+		return &ModelError{Message: fmt.Sprintf("failed to pull model %s: %s", model, reason), Model: model}
+	}
+
+	// ErrModelDeleteFailed is returned when deleting a model fails
+	ErrModelDeleteFailed = func(model string, reason string) error {
+		return &ModelError{Message: fmt.Sprintf("failed to delete model %s: %s", model, reason), Model: model}
+	}
+
+	// ErrGenerationFailed is returned when text generation fails
+	ErrGenerationFailed = func(reason string) error {
+		return &GenerationError{Message: fmt.Sprintf("generation failed: %s", reason)}
+	}
+
+	// ErrChatFailed is returned when chat fails
+	ErrChatFailed = func(reason string) error {
+		return &ChatError{Message: fmt.Sprintf("chat failed: %s", reason)}
+	}
+
+	// ErrEmbeddingFailed is returned when embedding generation fails
+	ErrEmbeddingFailed = func(reason string) error {
+		return &EmbeddingError{Message: fmt.Sprintf("embedding failed: %s", reason)}
+	}
+
+	// ErrConnectionFailed is returned when connection to Ollama fails
+	ErrConnectionFailed = func(reason string) error {
+		return &ConnectionError{Message: fmt.Sprintf("connection failed: %s", reason)}
+	}
+
+	// ErrTimeout is returned when a request times out
+	ErrTimeout = func(operation string) error {
+		return &TimeoutError{Message: fmt.Sprintf("timeout during %s", operation), Operation: operation}
+	}
+
+	// ErrRateLimitExceeded is returned when rate limit is exceeded
+	ErrRateLimitExceeded = func() error {
+		return &RateLimitError{Message: "rate limit exceeded"}
+	}
+)
+
+// ConfigError represents a configuration error
+type ConfigError struct {
+	Message string
+}
+
+func (e *ConfigError) Error() string {
+	return fmt.Sprintf("config error: %s", e.Message)
+}
+
+// RequestError represents a request validation error
+type RequestError struct {
+	Message string
+}
+
+func (e *RequestError) Error() string {
+	return fmt.Sprintf("request error: %s", e.Message)
+}
+
+// ModelError represents a model-related error
+type ModelError struct {
+	Message string
+	Model   string
+}
+
+func (e *ModelError) Error() string {
+	return fmt.Sprintf("model error: %s", e.Message)
+}
+
+// GenerationError represents a text generation error
+type GenerationError struct {
+	Message string
+}
+
+func (e *GenerationError) Error() string {
+	return fmt.Sprintf("generation error: %s", e.Message)
+}
+
+// ChatError represents a chat error
+type ChatError struct {
+	Message string
+}
+
+func (e *ChatError) Error() string {
+	return fmt.Sprintf("chat error: %s", e.Message)
+}
+
+// EmbeddingError represents an embedding generation error
+type EmbeddingError struct {
+	Message string
+}
+
+func (e *EmbeddingError) Error() string {
+	return fmt.Sprintf("embedding error: %s", e.Message)
+}
+
+// ConnectionError represents a connection error
+type ConnectionError struct {
+	Message string
+}
+
+func (e *ConnectionError) Error() string {
+	return fmt.Sprintf("connection error: %s", e.Message)
+}
+
+// TimeoutError represents a timeout error
+type TimeoutError struct {
+	Message   string
+	Operation string
+}
+
+func (e *TimeoutError) Error() string {
+	return fmt.Sprintf("timeout error: %s", e.Message)
+}
+
+// RateLimitError represents a rate limit error
+type RateLimitError struct {
+	Message string
+}
+
+func (e *RateLimitError) Error() string {
+	return fmt.Sprintf("rate limit error: %s", e.Message)
+}