rlox/src/result.rs

use crate::frontend::source_registry::{SourceRegistry, SourceSlice};
use std::fmt;

#[derive(Debug, Clone)]
pub enum LoxError {
    LexicalError {
        source_slice: SourceSlice,
        message: String,
    },
    RuntimeError {
        source_slice: SourceSlice,
        message: String,
    },
    ParseError {
        source_slice: SourceSlice,
        message: String,
    },
    IoError {
        message: String,
    },
    TypeMismatch {
        source_slice: SourceSlice,
        expected: String,
        found: String,
    },
}

/// Configuration for error display formatting
#[derive(Clone, Debug)]
pub struct ErrorDisplayConfig {
    /// Show colored output (for terminals that support it)
    pub colored: bool,
    /// Number of context lines to show before and after the error
    pub context_lines: usize,
    /// Show line numbers
    pub show_line_numbers: bool,
    /// Use Unicode characters for arrows and decorations
    pub use_unicode: bool,
}

impl Default for ErrorDisplayConfig {
    fn default() -> Self {
        Self {
            colored: true,
            context_lines: 2,
            show_line_numbers: true,
            use_unicode: true,
        }
    }
}

impl ErrorDisplayConfig {
    pub fn simple() -> Self {
        Self {
            colored: false,
            context_lines: 1,
            show_line_numbers: false,
            use_unicode: false,
        }
    }

    pub fn verbose() -> Self {
        Self {
            colored: true,
            context_lines: 3,
            show_line_numbers: true,
            use_unicode: true,
        }
    }
}

impl LoxError {
    pub fn get_message(&self) -> String {
        match self {
            LoxError::LexicalError { message, .. } => message.clone(),
            LoxError::RuntimeError { message, .. } => message.clone(),
            LoxError::ParseError { message, .. } => message.clone(),
            LoxError::IoError { message } => message.clone(),
            LoxError::TypeMismatch {
                expected, found, ..
            } => {
                format!("expected {}, found {}", expected, found)
            }
        }
    }

    pub fn get_source_slice(&self) -> Option<SourceSlice> {
        match self {
            LoxError::LexicalError { source_slice, .. } => Some(source_slice.clone()),
            LoxError::RuntimeError { source_slice, .. } => Some(source_slice.clone()),
            LoxError::ParseError { source_slice, .. } => Some(source_slice.clone()),
            LoxError::IoError { .. } => None,
            LoxError::TypeMismatch { source_slice, .. } => Some(source_slice.clone()),
        }
    }

    pub fn error_kind(&self) -> &'static str {
        match self {
            LoxError::LexicalError { .. } => "lexical error",
            LoxError::RuntimeError { .. } => "runtime error",
            LoxError::ParseError { .. } => "parse error",
            LoxError::IoError { .. } => "io error",
            LoxError::TypeMismatch { .. } => "type error",
        }
    }

    /// Display error with source code context using default configuration
    pub fn display_with_source(&self, source_registry: &SourceRegistry) -> String {
        self.display_with_source_and_config(source_registry, &ErrorDisplayConfig::default())
    }

    /// Display error with source code context using custom configuration
    pub fn display_with_source_and_config(
        &self,
        source_registry: &SourceRegistry,
        config: &ErrorDisplayConfig,
    ) -> String {
        let mut output = String::new();

        // Error header
        let header = if config.colored {
            format!(
                "\x1b[1;31merror\x1b[0m: [{}] {}",
                self.error_kind(),
                self.get_message()
            )
        } else {
            format!("error: [{}] {}", self.error_kind(), self.get_message())
        };
        output.push_str(&header);
        output.push('\n');

        // If we have source location, show it
        if let Some(source_slice) = self.get_source_slice() {
            let source_info = source_registry.get_by_id(source_slice.source_id);

            // File location line
            let location = if config.colored {
                format!(
                    "  \x1b[34m-->\x1b[0m {}:{}:{}",
                    source_info.file_name,
                    source_slice.start_position.line + 1,
                    source_slice.start_position.column + 1
                )
            } else {
                format!(
                    "  --> {}:{}:{}",
                    source_info.file_name,
                    source_slice.start_position.line + 1,
                    source_slice.start_position.column + 1
                )
            };
            output.push_str(&location);
            output.push('\n');

            // Source code context
            if let Some(source_context) =
                self.get_source_context(source_registry, &source_slice, config)
            {
                output.push_str(&source_context);
            }
        }

        output
    }

    fn get_source_context(
        &self,
        source_registry: &SourceRegistry,
        source_slice: &SourceSlice,
        config: &ErrorDisplayConfig,
    ) -> Option<String> {
        let source_info = source_registry.get_by_id(source_slice.source_id);
        let lines: Vec<&str> = source_info.content.lines().collect();

        if lines.is_empty() || source_slice.start_position.line >= lines.len() {
            return None;
        }

        let mut output = String::new();
        let error_line = source_slice.start_position.line;
        let start_line = error_line.saturating_sub(config.context_lines);
        let end_line = (error_line + config.context_lines + 1).min(lines.len());

        // Calculate the width needed for line numbers
        let line_number_width = if config.show_line_numbers {
            (end_line + 1).to_string().len()
        } else {
            0
        };

        // Show context lines
        for line_idx in start_line..end_line {
            let line_content = lines[line_idx];
            let line_number = line_idx + 1;

            if config.show_line_numbers {
                let line_num_str = if config.colored {
                    if line_idx == error_line {
                        format!(
                            "\x1b[1;34m{:width$}\x1b[0m",
                            line_number,
                            width = line_number_width
                        )
                    } else {
                        format!(
                            "\x1b[34m{:width$}\x1b[0m",
                            line_number,
                            width = line_number_width
                        )
                    }
                } else {
                    format!("{:width$}", line_number, width = line_number_width)
                };

                let separator = if config.colored {
                    if line_idx == error_line {
                        "\x1b[1;34m |\x1b[0m "
                    } else {
                        "\x1b[34m |\x1b[0m "
                    }
                } else {
                    " | "
                };

                output.push_str(&format!(
                    "   {}{}{}\n",
                    line_num_str, separator, line_content
                ));
            } else {
                output.push_str(&format!("   {}\n", line_content));
            }

            // Add error indicator on the error line
            if line_idx == error_line {
                let spaces_before =
                    " ".repeat(3 + line_number_width + 3 + source_slice.start_position.column);

                let error_length = if source_slice.start_position.line
                    == source_slice.end_position.line
                {
                    (source_slice.end_position.column - source_slice.start_position.column).max(1)
                } else {
                    line_content.len() - source_slice.start_position.column
                };

                let indicator = if config.use_unicode {
                    "^".repeat(error_length)
                } else {
                    "^".repeat(error_length)
                };

                let colored_indicator = if config.colored {
                    format!("\x1b[1;31m{}\x1b[0m", indicator)
                } else {
                    indicator
                };

                // Add the indicator line
                if config.show_line_numbers {
                    let empty_line_number = " ".repeat(line_number_width);
                    let separator = if config.colored {
                        "\x1b[34m |\x1b[0m "
                    } else {
                        " | "
                    };
                    output.push_str(&format!(
                        "   {}{}{}{}\n",
                        empty_line_number,
                        separator,
                        spaces_before[3 + line_number_width + 3..].to_string(),
                        colored_indicator
                    ));
                } else {
                    output.push_str(&format!(
                        "   {}{}\n",
                        spaces_before[3..].to_string(),
                        colored_indicator
                    ));
                }

                // Add error type and additional context
                let error_note = match self {
                    LoxError::TypeMismatch {
                        expected, found, ..
                    } => Some(format!("expected `{}`, found `{}`", expected, found)),
                    _ => None,
                };

                if let Some(note) = error_note {
                    let note_prefix = if config.show_line_numbers {
                        format!(
                            "   {} {} ",
                            " ".repeat(line_number_width),
                            if config.colored {
                                "\x1b[34m|\x1b[0m"
                            } else {
                                "|"
                            }
                        )
                    } else {
                        "   ".to_string()
                    };

                    let colored_note = if config.colored {
                        format!("\x1b[1;36mnote\x1b[0m: {}", note)
                    } else {
                        format!("note: {}", note)
                    };

                    output.push_str(&format!("{}{}\n", note_prefix, colored_note));
                }
            }
        }

        Some(output)
    }

    /// Print error with source context to stdout
    pub fn print_with_source(&self, source_registry: &SourceRegistry) {
        println!("{}", self.display_with_source(source_registry));
    }

    /// Print error with source context and custom config to stdout
    pub fn print_with_source_and_config(
        &self,
        source_registry: &SourceRegistry,
        config: &ErrorDisplayConfig,
    ) {
        println!(
            "{}",
            self.display_with_source_and_config(source_registry, config)
        );
    }

    /// Legacy method for backwards compatibility
    pub fn print_with_context(&self, source_registry: &SourceRegistry) {
        self.print_with_source(source_registry);
    }
}

impl fmt::Display for LoxError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            LoxError::LexicalError {
                source_slice,
                message,
            } => {
                write!(
                    f,
                    "Lexical error at {}:{}: {}",
                    source_slice.start_position.line + 1,
                    source_slice.start_position.column + 1,
                    message
                )
            }
            LoxError::RuntimeError {
                source_slice,
                message,
            } => {
                write!(
                    f,
                    "Runtime error at {}:{}: {}",
                    source_slice.start_position.line + 1,
                    source_slice.start_position.column + 1,
                    message
                )
            }
            LoxError::ParseError {
                source_slice,
                message,
            } => {
                write!(
                    f,
                    "Parse error at {}:{}: {}",
                    source_slice.start_position.line + 1,
                    source_slice.start_position.column + 1,
                    message
                )
            }
            LoxError::IoError { message } => write!(f, "IO error: {}", message),
            LoxError::TypeMismatch {
                source_slice,
                expected,
                found,
            } => {
                write!(
                    f,
                    "Type mismatch at {}:{}: expected `{}`, found `{}`",
                    source_slice.start_position.line + 1,
                    source_slice.start_position.column + 1,
                    expected,
                    found
                )
            }
        }
    }
}

impl std::error::Error for LoxError {}

pub type LoxResult<T> = Result<T, LoxError>;

/// Helper function to create a lexical error
pub fn lexical_error(source_slice: SourceSlice, message: impl Into<String>) -> LoxError {
    LoxError::LexicalError {
        source_slice,
        message: message.into(),
    }
}

/// Helper function to create a parse error
pub fn parse_error(source_slice: SourceSlice, message: impl Into<String>) -> LoxError {
    LoxError::ParseError {
        source_slice,
        message: message.into(),
    }
}

/// Helper function to create a runtime error
pub fn runtime_error(source_slice: SourceSlice, message: impl Into<String>) -> LoxError {
    LoxError::RuntimeError {
        source_slice,
        message: message.into(),
    }
}

/// Helper function to create a type mismatch error
pub fn type_mismatch_error(
    source_slice: SourceSlice,
    expected: impl Into<String>,
    found: impl Into<String>,
) -> LoxError {
    LoxError::TypeMismatch {
        source_slice,
        expected: expected.into(),
        found: found.into(),
    }
}

/// Helper function to create an IO error
pub fn io_error(message: impl Into<String>) -> LoxError {
    LoxError::IoError {
        message: message.into(),
    }
}