package tools

import "encoding/json"

// ToolResult represents the structured return value from tool execution.
// It provides clear semantics for different types of results and supports
// async operations, user-facing messages, and error handling.
type ToolResult struct {
	// ForLLM is the content sent to the LLM for context.
	// Required for all results.
	ForLLM string `json:"for_llm"`

	// ForUser is the content sent directly to the user.
	// If empty, no user message is sent.
	// Silent=true overrides this field.
	ForUser string `json:"for_user,omitempty"`

	// Silent suppresses sending any message to the user.
	// When true, ForUser is ignored even if set.
	Silent bool `json:"silent"`

	// IsError indicates whether the tool execution failed.
	// When true, the result should be treated as an error.
	IsError bool `json:"is_error"`

	// Async indicates whether the tool is running asynchronously.
	// When true, the tool will complete later and notify via callback.
	Async bool `json:"async"`

	// Err is the underlying error (not JSON serialized).
	// Used for internal error handling and logging.
	Err error `json:"-"`
}

// NewToolResult creates a basic ToolResult with content for the LLM.
// Use this when you need a simple result with default behavior.
//
// Example:
//
//	result := NewToolResult("File updated successfully")
func NewToolResult(forLLM string) *ToolResult {
	return &ToolResult{
		ForLLM: forLLM,
	}
}

// SilentResult creates a ToolResult that is silent (no user message).
// The content is only sent to the LLM for context.
//
// Use this for operations that should not spam the user, such as:
// - File reads/writes
// - Status updates
// - Background operations
//
// Example:
//
//	result := SilentResult("Config file saved")
func SilentResult(forLLM string) *ToolResult {
	return &ToolResult{
		ForLLM:  forLLM,
		Silent:  true,
		IsError: false,
		Async:   false,
	}
}

// AsyncResult creates a ToolResult for async operations.
// The task will run in the background and complete later.
//
// Use this for long-running operations like:
// - Subagent spawns
// - Background processing
// - External API calls with callbacks
//
// Example:
//
//	result := AsyncResult("Subagent spawned, will report back")
func AsyncResult(forLLM string) *ToolResult {
	return &ToolResult{
		ForLLM:  forLLM,
		Silent:  false,
		IsError: false,
		Async:   true,
	}
}

// ErrorResult creates a ToolResult representing an error.
// Sets IsError=true and includes the error message.
//
// Example:
//
//	result := ErrorResult("Failed to connect to database: connection refused")
func ErrorResult(message string) *ToolResult {
	return &ToolResult{
		ForLLM:  message,
		Silent:  false,
		IsError: true,
		Async:   false,
	}
}

// UserResult creates a ToolResult with content for both LLM and user.
// Both ForLLM and ForUser are set to the same content.
//
// Use this when the user needs to see the result directly:
// - Command execution output
// - Fetched web content
// - Query results
//
// Example:
//
//	result := UserResult("Total files found: 42")
func UserResult(content string) *ToolResult {
	return &ToolResult{
		ForLLM:  content,
		ForUser: content,
		Silent:  false,
		IsError: false,
		Async:   false,
	}
}

// MarshalJSON implements custom JSON serialization.
// The Err field is excluded from JSON output via the json:"-" tag.
func (tr *ToolResult) MarshalJSON() ([]byte, error) {
	type Alias ToolResult
	return json.Marshal(&struct {
		*Alias
	}{
		Alias: (*Alias)(tr),
	})
}

// WithError sets the Err field and returns the result for chaining.
// This preserves the error for logging while keeping it out of JSON.
//
// Example:
//
//	result := ErrorResult("Operation failed").WithError(err)
func (tr *ToolResult) WithError(err error) *ToolResult {
	tr.Err = err
	return tr
}