package errors

import (
	"fmt"
	"runtime"
	"time"
)

// ErrorCategory represents the category of an error
type ErrorCategory string

const (
	CategoryNetwork       ErrorCategory = "NETWORK"       // RPC, DNS, connection issues
	CategoryParsing       ErrorCategory = "PARSING"       // ABI decoding, transaction parsing
	CategoryValidation    ErrorCategory = "VALIDATION"    // Input validation, data validation
	CategoryExecution     ErrorCategory = "EXECUTION"     // Transaction execution, contract calls
	CategoryConfiguration ErrorCategory = "CONFIGURATION" // Config loading, invalid settings
	CategoryDatabase      ErrorCategory = "DATABASE"      // Database operations
	CategorySecurity      ErrorCategory = "SECURITY"      // Security violations, unauthorized access
	CategoryMath          ErrorCategory = "MATH"          // Arithmetic errors, overflow/underflow
	CategoryInternal      ErrorCategory = "INTERNAL"      // Internal logic errors, unexpected state
	CategoryExternal      ErrorCategory = "EXTERNAL"      // External service failures
	CategoryUnknown       ErrorCategory = "UNKNOWN"       // Uncategorized errors
)

// ErrorSeverity represents how critical an error is
type ErrorSeverity string

const (
	SeverityDebug    ErrorSeverity = "DEBUG"    // Informational, not an actual error
	SeverityInfo     ErrorSeverity = "INFO"     // Notable but not problematic
	SeverityWarning  ErrorSeverity = "WARNING"  // Potential issue, should investigate
	SeverityError    ErrorSeverity = "ERROR"    // Actual error, functionality impacted
	SeverityCritical ErrorSeverity = "CRITICAL" // Critical error, immediate attention required
	SeverityFatal    ErrorSeverity = "FATAL"    // Fatal error, system cannot continue
)

// StructuredError represents a comprehensive error with full context
type StructuredError struct {
	// Core error information
	Message  string        // Human-readable error message
	Category ErrorCategory // Error category for classification
	Severity ErrorSeverity // How critical is this error

	// Origin tracking
	File     string // Source file where error occurred
	Function string // Function where error occurred
	Line     int    // Line number where error occurred
	Package  string // Go package where error occurred

	// Context
	Reason        string                 // Why this error occurred (root cause)
	Action        string                 // What the code was trying to do when it failed
	Impact        string                 // Impact of this error on the system
	Suggestion    string                 // Suggested fix or next steps
	Details       map[string]interface{} // Additional structured context
	UnderlyingErr error                  // Original error if wrapping

	// Metadata
	Timestamp time.Time // When the error occurred
	ErrorID   string    // Unique identifier for this error instance
}

// Error implements the error interface
func (e *StructuredError) Error() string {
	if e.UnderlyingErr != nil {
		return fmt.Sprintf("[%s/%s] %s: %v (in %s:%d)",
			e.Category, e.Severity, e.Message, e.UnderlyingErr, e.File, e.Line)
	}
	return fmt.Sprintf("[%s/%s] %s (in %s:%d)",
		e.Category, e.Severity, e.Message, e.File, e.Line)
}

// Unwrap returns the underlying error for error chain support
func (e *StructuredError) Unwrap() error {
	return e.UnderlyingErr
}

// NewStructuredError creates a new structured error with automatic caller tracking
func NewStructuredError(category ErrorCategory, severity ErrorSeverity, message string) *StructuredError {
	return newStructuredErrorWithDepth(category, severity, message, 2)
}

// newStructuredErrorWithDepth creates a structured error with custom stack depth
func newStructuredErrorWithDepth(category ErrorCategory, severity ErrorSeverity, message string, depth int) *StructuredError {
	// Get caller information
	pc, file, line, ok := runtime.Caller(depth)
	if !ok {
		file = "unknown"
		line = 0
	}

	funcName := "unknown"
	packageName := "unknown"
	if fn := runtime.FuncForPC(pc); fn != nil {
		funcName = fn.Name()
		// Extract package name from function name (format: "package/path.FunctionName")
		for i := len(funcName) - 1; i >= 0; i-- {
			if funcName[i] == '/' {
				packageName = funcName[:i]
				break
			}
		}
	}

	// Generate unique error ID
	errorID := fmt.Sprintf("ERR-%d-%s", time.Now().UnixNano(), category)

	return &StructuredError{
		Message:   message,
		Category:  category,
		Severity:  severity,
		File:      file,
		Function:  funcName,
		Line:      line,
		Package:   packageName,
		Details:   make(map[string]interface{}),
		Timestamp: time.Now(),
		ErrorID:   errorID,
	}
}

// WithReason adds the reason (root cause) for the error
func (e *StructuredError) WithReason(reason string) *StructuredError {
	e.Reason = reason
	return e
}

// WithAction describes what the code was trying to do
func (e *StructuredError) WithAction(action string) *StructuredError {
	e.Action = action
	return e
}

// WithImpact describes the impact of this error
func (e *StructuredError) WithImpact(impact string) *StructuredError {
	e.Impact = impact
	return e
}

// WithSuggestion provides a suggestion for fixing or handling the error
func (e *StructuredError) WithSuggestion(suggestion string) *StructuredError {
	e.Suggestion = suggestion
	return e
}

// WithDetail adds a key-value detail to the error context
func (e *StructuredError) WithDetail(key string, value interface{}) *StructuredError {
	e.Details[key] = value
	return e
}

// WithDetails adds multiple details at once
func (e *StructuredError) WithDetails(details map[string]interface{}) *StructuredError {
	for k, v := range details {
		e.Details[k] = v
	}
	return e
}

// Wrap wraps an underlying error with structured context
func (e *StructuredError) Wrap(err error) *StructuredError {
	e.UnderlyingErr = err
	return e
}

// FormatForLogging returns a comprehensive string representation for logging
func (e *StructuredError) FormatForLogging() string {
	result := fmt.Sprintf(
		"[%s] %s/%s: %s\n"+
			"  Origin: %s:%d (%s)\n"+
			"  ErrorID: %s\n"+
			"  Timestamp: %s\n",
		e.ErrorID,
		e.Category,
		e.Severity,
		e.Message,
		e.File,
		e.Line,
		e.Function,
		e.ErrorID,
		e.Timestamp.Format(time.RFC3339),
	)

	if e.Reason != "" {
		result += fmt.Sprintf("  Reason: %s\n", e.Reason)
	}

	if e.Action != "" {
		result += fmt.Sprintf("  Action: %s\n", e.Action)
	}

	if e.Impact != "" {
		result += fmt.Sprintf("  Impact: %s\n", e.Impact)
	}

	if e.Suggestion != "" {
		result += fmt.Sprintf("  Suggestion: %s\n", e.Suggestion)
	}

	if len(e.Details) > 0 {
		result += "  Details:\n"
		for k, v := range e.Details {
			result += fmt.Sprintf("    - %s: %v\n", k, v)
		}
	}

	if e.UnderlyingErr != nil {
		result += fmt.Sprintf("  Underlying: %v\n", e.UnderlyingErr)
	}

	return result
}

// FormatCompact returns a single-line representation
func (e *StructuredError) FormatCompact() string {
	compact := fmt.Sprintf("[%s/%s] %s", e.Category, e.Severity, e.Message)

	if e.Reason != "" {
		compact += fmt.Sprintf(" | Reason: %s", e.Reason)
	}

	if e.Action != "" {
		compact += fmt.Sprintf(" | Action: %s", e.Action)
	}

	compact += fmt.Sprintf(" | Origin: %s:%d", e.File, e.Line)

	if e.UnderlyingErr != nil {
		compact += fmt.Sprintf(" | Underlying: %v", e.UnderlyingErr)
	}

	return compact
}

// Helper functions for common error patterns

// NetworkError creates a network-related error
func NetworkError(message string) *StructuredError {
	return newStructuredErrorWithDepth(CategoryNetwork, SeverityError, message, 2)
}

// ParsingError creates a parsing-related error
func ParsingError(message string) *StructuredError {
	return newStructuredErrorWithDepth(CategoryParsing, SeverityError, message, 2)
}

// ValidationError creates a validation-related error
func ValidationError(message string) *StructuredError {
	return newStructuredErrorWithDepth(CategoryValidation, SeverityWarning, message, 2)
}

// ExecutionError creates an execution-related error
func ExecutionError(message string) *StructuredError {
	return newStructuredErrorWithDepth(CategoryExecution, SeverityCritical, message, 2)
}

// ConfigurationError creates a configuration-related error
func ConfigurationError(message string) *StructuredError {
	return newStructuredErrorWithDepth(CategoryConfiguration, SeverityCritical, message, 2)
}

// InternalError creates an internal logic error
func InternalError(message string) *StructuredError {
	return newStructuredErrorWithDepth(CategoryInternal, SeverityError, message, 2)
}

// MathError creates a mathematical error
func MathError(message string) *StructuredError {
	return newStructuredErrorWithDepth(CategoryMath, SeverityError, message, 2)
}

// SecurityError creates a security-related error
func SecurityError(message string) *StructuredError {
	return newStructuredErrorWithDepth(CategorySecurity, SeverityCritical, message, 2)
}