qanglang-core 0.1.0

use std::{ops::Range, sync::Arc};

use crate::{SourceMap, Vm, backend::chunk::SourceLocation, nodes::SourceSpan};

#[derive(Debug, Clone, Copy, PartialEq)]
pub enum ErrorMessageFormat {
    Verbose,
    Compact,
    Minimal,
}

#[derive(Debug, Clone, PartialEq)]
pub struct QangPipelineError(Vec<QangCompilerError>);

impl QangPipelineError {
    pub fn new(errors: Vec<QangCompilerError>) -> Self {
        Self(errors)
    }

    pub fn all(&self) -> &[QangCompilerError] {
        &self.0
    }

    pub fn into_errors(self) -> Vec<QangCompilerError> {
        self.0
    }
}

#[derive(Debug, Clone, PartialEq, Copy)]
pub enum QangErrorKind {
    Syntax,
    Analysis,
    Assembler,
}

impl std::fmt::Display for QangErrorKind {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::Syntax => write!(f, "Syntax Error"),
            Self::Analysis => write!(f, "Analysis Error"),
            Self::Assembler => write!(f, "Assembler Error"),
        }
    }
}

#[derive(Debug, Clone, PartialEq)]
pub struct QangCompilerError {
    pub message: String,
    pub span: SourceSpan,
    pub kind: QangErrorKind,
    pub source_map: Arc<SourceMap>,
}

impl QangCompilerError {
    pub fn new_syntax_error(message: String, span: SourceSpan, source_map: Arc<SourceMap>) -> Self {
        Self {
            message,
            span,
            kind: QangErrorKind::Syntax,
            source_map,
        }
    }

    pub fn new_analysis_error(
        message: String,
        span: SourceSpan,
        source_map: Arc<SourceMap>,
    ) -> Self {
        Self {
            message,
            span,
            kind: QangErrorKind::Analysis,
            source_map,
        }
    }

    pub fn new_assembler_error(
        message: String,
        span: SourceSpan,
        source_map: Arc<SourceMap>,
    ) -> Self {
        Self {
            message,
            span,
            kind: QangErrorKind::Assembler,
            source_map,
        }
    }

    pub fn into_formatted(self) -> Self {
        let message = pretty_print_error(&self.source_map, self.kind, &self.message, self.span);

        Self {
            message,
            span: self.span,
            kind: self.kind,
            source_map: self.source_map,
        }
    }

    pub fn into_short_formatted(self) -> Self {
        let line_num = self.source_map.get_line_number(self.span.start);
        let col_num = self.source_map.get_column_number(self.span.start);

        let message = format!(
            "{} at line {}, column {}: {}\n",
            self.kind, line_num, col_num, self.message
        );

        Self {
            message,
            span: self.span,
            kind: self.kind,
            source_map: self.source_map,
        }
    }
}

impl std::fmt::Display for QangCompilerError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.message)
    }
}

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

#[derive(Debug, Clone)]
pub struct NativeFunctionError(pub String);

impl NativeFunctionError {
    pub fn new(message: &str) -> Self {
        Self(message.to_string())
    }

    pub fn into_qang_error(self, loc: SourceLocation) -> QangRuntimeError {
        QangRuntimeError::new(self.0, loc)
    }
}

impl From<&'static str> for NativeFunctionError {
    fn from(value: &'static str) -> Self {
        NativeFunctionError::new(value)
    }
}

#[derive(Debug, Clone, PartialEq)]
pub struct Trace {
    callee: String,
    module: Option<String>,
    loc: SourceLocation,
}

impl Trace {
    pub fn new(callee: &str, loc: SourceLocation) -> Self {
        Self {
            callee: callee.to_string(),
            module: None,
            loc,
        }
    }

    pub fn new_with_module(callee: &str, module: &str, loc: SourceLocation) -> Self {
        Self {
            callee: callee.to_string(),
            module: Some(module.to_string()),
            loc,
        }
    }
}

impl std::fmt::Display for Trace {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        if let Some(module) = &self.module {
            write!(
                f,
                "  at {} in {} (line {}, column {})",
                self.callee, module, self.loc.line, self.loc.col
            )
        } else {
            write!(
                f,
                "  at {} (line {}, column {})",
                self.callee, self.loc.line, self.loc.col
            )
        }
    }
}

#[derive(Debug, Clone, PartialEq)]
pub struct QangRuntimeError {
    pub message: String,
    pub stack_trace: Vec<Trace>,
}

impl QangRuntimeError {
    pub fn new(message: String, loc: SourceLocation) -> Self {
        Self {
            message: format!(
                "Runtime Error at line {}, column {}: {}",
                loc.line, loc.col, message
            )
            .to_string(),
            stack_trace: Vec::new(),
        }
    }

    pub fn with_stack_trace(mut self, stack_trace: Vec<Trace>) -> Self {
        self.stack_trace = stack_trace;
        self
    }
}

impl std::fmt::Display for QangRuntimeError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.message)?;
        if !self.stack_trace.is_empty() {
            writeln!(f)?;
            writeln!(f, "Stack trace:")?;
            for trace in &self.stack_trace {
                writeln!(f, "{}", trace)?;
            }
        }
        Ok(())
    }
}

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

#[derive(Debug, Clone, Default)]
pub struct ErrorReporter {
    errors: Vec<QangCompilerError>,
}

impl ErrorReporter {
    pub fn new() -> Self {
        Self { errors: Vec::new() }
    }

    pub fn report_error(&mut self, error: QangCompilerError) {
        self.errors.push(error);
    }

    pub fn has_errors(&self) -> bool {
        !self.errors.is_empty()
    }

    pub fn errors(&self) -> &[QangCompilerError] {
        &self.errors
    }

    pub fn take_errors(&mut self) -> Vec<QangCompilerError> {
        std::mem::take(&mut self.errors)
    }

    pub fn merge(&mut self, mut other: Self) {
        self.errors.extend(other.take_errors());
    }
}

pub fn pretty_print_error(
    source_map: &SourceMap,
    kind: QangErrorKind,
    message: &str,
    span: SourceSpan,
) -> String {
    let mut output = String::new();

    let line_num = source_map.get_line_number(span.start);
    let col_num = source_map.get_column_number(span.start);

    // Error header with kind
    output.push_str(&format!(
        "{} at line {}, column {}: {}\n",
        kind, line_num, col_num, message
    ));

    // Get the problematic line
    let line_chars = source_map.get_line(line_num);
    let line_str: String = line_chars.iter().collect();

    // Line number padding for alignment
    let line_num_str = line_num.to_string();
    let padding = " ".repeat(line_num_str.len());

    // Show the line with line number
    output.push_str(&format!(" {} | {}\n", line_num, line_str));

    // Create the error pointer
    let error_pointer = create_error_pointer(source_map, span, &line_str, col_num);
    output.push_str(&format!(" {} | {}\n", padding, error_pointer));

    output
}

fn create_error_pointer(
    source_map: &SourceMap,
    span: SourceSpan,
    line_str: &str,
    col_num: u32,
) -> String {
    let mut pointer = String::new();

    // Add spaces up to the error column
    for i in 1..col_num {
        if i <= line_str.len() as u32 {
            let ch = line_str.chars().nth((i - 1) as usize).unwrap_or(' ');
            if ch == '\t' {
                pointer.push('\t');
            } else {
                pointer.push(' ');
            }
        } else {
            pointer.push(' ');
        }
    }

    // Calculate the span length within the line
    let start_col = source_map.get_column_number(span.start) as usize;
    let end_col = source_map.get_column_number(span.end.saturating_sub(1)) as usize;

    // Add the error indicators
    if start_col == end_col || span.start == span.end {
        pointer.push('^');
    } else {
        // Multi-character span
        let span_length = (end_col - start_col + 1).max(1);
        for i in 0..span_length {
            if i == 0 {
                pointer.push('^');
            } else {
                pointer.push('~');
            }
        }
    }

    pointer
}

impl Vm {
    pub fn get_stack_trace(&self) -> Vec<Trace> {
        self.get_stack_trace_from_frames(0..self.state.frame_count)
    }

    fn get_stack_trace_from_frames(&self, frame_id_range: Range<usize>) -> Vec<Trace> {
        let mut traces = Vec::new();
        let mut previous_module: Option<String> = None;

        for frame_idx in frame_id_range {
            let frame = &self.state.frames[frame_idx];
            let closure = self.alloc.closures.get_closure(frame.closure);
            let function = self.alloc.get_function(closure.function);

            // this will clean the canonical path if it has a matching prefix,otherwise return the input value.
            // Because functions syntatically cannot start with a `/` or `.`, this will not modify declared function names.
            let name = &clean_canonicalized_path(self.alloc.strings.get_string(function.name));

            let loc = if frame.ip > 0 {
                function
                    .chunk
                    .locs
                    .get(frame.ip - 1)
                    .copied()
                    .unwrap_or_default()
            } else {
                SourceLocation::default()
            };

            // Get current module name if closure has module context
            let current_module = closure.module_context.map(|module_handle| {
                let module_string_handle = self.state.modules.get_module_id(module_handle);
                let raw_path = self.alloc.strings.get_string(module_string_handle);
                clean_canonicalized_path(raw_path)
            });

            // Only include module name if it's different from the previous frame
            let should_show_module = match (&previous_module, &current_module) {
                (None, Some(_)) => true,                  // First module encountered
                (Some(prev), Some(curr)) => prev != curr, // Module changed
                _ => false,                               // No module or same module
            };

            if should_show_module {
                if let Some(module_name) = &current_module {
                    traces.push(Trace::new_with_module(name, module_name, loc));
                } else {
                    traces.push(Trace::new(name, loc));
                }
            } else {
                traces.push(Trace::new(name, loc));
            }

            previous_module = current_module;
        }

        traces
    }
}

fn clean_canonicalized_path(path: &str) -> String {
    // Remove Windows UNC prefix
    #[cfg(target_os = "windows")]
    if let Some(stripped) = path.strip_prefix(r"\\?\") {
        return stripped.to_string();
    }

    // Remove leading "./" on Unix systems
    #[cfg(not(target_os = "windows"))]
    if let Some(stripped) = path.strip_prefix("./") {
        return stripped.to_string();
    }

    path.to_string()
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::SourceMap;

    fn error_summary(errors: &[QangCompilerError]) -> String {
        if errors.is_empty() {
            "No errors found.".to_string()
        } else if errors.len() == 1 {
            "Found 1 error.".to_string()
        } else {
            format!("Found {} errors.", errors.len())
        }
    }

    #[test]
    fn test_error_reporter_basic_functionality() {
        let source = "var x = 5 +\nvar y = 10;";
        let source_map = SourceMap::from_source(source.to_string());
        let mut reporter = ErrorReporter::new();

        // Report an error
        reporter.report_error(
            QangCompilerError::new_syntax_error(
                "Expected expression after '+'".to_string(),
                SourceSpan::new(11, 11),
                Arc::new(source_map),
            )
            .into_formatted(),
        );

        assert!(reporter.has_errors());
        assert_eq!(reporter.errors().len(), 1);
    }

    #[test]
    fn test_multiple_errors() {
        let source = "var x = 5 +\nvar y = 10 *\nvar z;";
        let source_map = SourceMap::from_source(source.to_string());
        let source_map = Arc::new(source_map);
        let mut reporter = ErrorReporter::new();

        // Report multiple errors
        reporter.report_error(
            QangCompilerError::new_syntax_error(
                "Missing operand after '+'".to_string(),
                SourceSpan::new(11, 11),
                source_map.clone(),
            )
            .into_formatted(),
        );

        reporter.report_error(
            QangCompilerError::new_syntax_error(
                "Missing operand after '*'".to_string(),
                SourceSpan::new(23, 23),
                source_map,
            )
            .into_formatted(),
        );

        assert_eq!(reporter.errors().len(), 2);

        let summary = error_summary(reporter.errors());
        assert_eq!(summary, "Found 2 errors.");
    }

    #[test]
    fn test_error_summary_no_errors() {
        let reporter = ErrorReporter::new();

        let summary = error_summary(reporter.errors());
        assert!(summary.contains("No errors found."));
    }

    #[test]
    fn test_error_summary_single_errors() {
        let source = "var x = 5;";
        let source_map = SourceMap::from_source(source.to_string());
        let mut reporter = ErrorReporter::new();

        reporter.report_error(
            QangCompilerError::new_syntax_error(
                "Syntax error 1".to_string(),
                SourceSpan::new(0, 3),
                Arc::new(source_map),
            )
            .into_formatted(),
        );

        let summary = error_summary(reporter.errors());
        assert!(summary.contains("Found 1 error."));
    }

    #[test]
    fn test_error_summary_multiple_errors() {
        let source = "var x = 5;";
        let source_map = SourceMap::from_source(source.to_string());
        let source_map = Arc::new(source_map);
        let mut reporter = ErrorReporter::new();

        reporter.report_error(
            QangCompilerError::new_syntax_error(
                "Syntax error 1".to_string(),
                SourceSpan::new(0, 3),
                source_map.clone(),
            )
            .into_formatted(),
        );
        reporter.report_error(
            QangCompilerError::new_syntax_error(
                "Syntax error 2".to_string(),
                SourceSpan::new(4, 5),
                source_map,
            )
            .into_formatted(),
        );

        let summary = error_summary(reporter.errors());
        assert!(summary.contains("Found 2 errors."));
    }
}