uxn-tal 0.1.6

//! ROM file generation and management

use crate::error::{AssemblerError, Result};
use std::io::Write;

/// Represents a UXN ROM file
pub struct Rom {
    data: Vec<u8>,
    position: u16,
    size: usize,
    source: Option<String>,
    path: Option<String>,
    /// Track last non-zero end address like uxnasm's `length`
    /// It is the next address after the last non-zero write.
    /// Initialized to PAGE(0x0100).
    /// This keeps trailing zeros (e.g., from $) out of the output.
    length: usize,
}

impl Rom {
    /// Create a new ROM instance
    pub fn new() -> Self {
        Self {
            data: vec![0; 0x10000],
            position: 0x0100, // Start at 0x0100 like uxnasm does
            size: 0,
            source: None,
            path: None,
            length: 0x0100,
        }
    }

    pub fn set_source(&mut self, source: Option<String>) {
        self.source = source;
    }

    pub fn get_source_line(&self, line: Option<usize>) -> String {
        if let Some(src) = &self.source {
            match line {
            Some(line) if line > 0 => src.lines().nth(line - 1).map(|s| s.to_string()).unwrap_or_default(),
            None => src.clone(),
            _ => String::new(),
            }
        } else {
            String::new()
        }
    }

    pub fn source(&self) -> Option<&String> {
        self.source.as_ref()
    }
    /// Returns the source path if available
    pub fn source_path(&self) -> Option<&String> {
        self.path.as_ref()
    }
    pub fn set_path(&mut self, path: Option<String>) {
        self.path = path;
    }
    /// Write a byte to the ROM at the current position
    pub fn write_byte(&mut self, byte: u8) -> Result<()> {
        if self.position as usize >= 65536 {
            return Err(AssemblerError::RomTooLarge {
                size: self.position as usize + 1,
            });
        }
        self.data[self.position as usize] = byte;
        self.position += 1;
        self.size = self.size.max(self.position as usize);
        // Match uxnasm: only extend length on non-zero writes
        if byte != 0 {
            self.length = self.length.max(self.position as usize);
        }
        Ok(())
    }

    /// Write a 16-bit value at the current position (big-endian: high byte first)
    pub fn write_short(&mut self, value: u16) -> Result<()> {
        self.write_byte((value >> 8) as u8)?;
        self.write_byte((value & 0xff) as u8)?;
        Ok(())
    }

    // Write a 16-bit value at a specific address (big-endian: high byte first)
    pub fn write_short_at(&mut self, address: u16, value: u16) -> Result<()> {
        self.write_byte_at(address,     (value >> 8) as u8)?; // high
        self.write_byte_at(address + 1, (value & 0xff) as u8)?; // low
        Ok(())
    }

    /// Pad the ROM to a specific address
    pub fn pad_to(&mut self, address: u16) -> Result<()> {
        if address as usize > 65536 {
            return Err(AssemblerError::InvalidPadding { address });
        }
        self.position = address;
        self.size = self.size.max(address as usize);
        // Don't touch `length` here; padding doesn't contribute data.
        Ok(())
    }

    /// Get the current position in the ROM
    pub fn position(&self) -> u16 {
        self.position
    }

    /// Set the current position in the ROM
    pub fn set_position(&mut self, position: u16) -> Result<()> {
        if position as usize > 65536 {
            return Err(AssemblerError::InvalidPadding { address: position });
        }
        self.position = position;
        self.size = self.size.max(position as usize);
        Ok(())
    }

    /// Get the ROM data as a slice, trimmed to actual size
    pub fn data(&self) -> &[u8] {
        let start = 0x0100;
        let end = self.length.clamp(start, self.data.len());
        if end <= start || end > self.data.len() {
            &[]
        } else {
            // Do NOT trim leading zeros; uxnasm writes [PAGE..length).
            &self.data[start..end]
        }
    }

    /// Returns true if any byte in the zero page (0x0000..0x0100) is nonzero
    pub fn has_zero_page_data(&self) -> bool {
        if self.data.len() < 0x0100 {
            return false;
        }
        self.data[..0x0100].iter().any(|&b| b != 0)
    }

    /// Get the size of the ROM
    pub fn len(&self) -> usize {
        let start = 0x0100;
        let end = self.length.clamp(start, self.data.len());
        end.saturating_sub(start)
    }

    /// Check if the ROM is empty
    pub fn is_empty(&self) -> bool {
        self.length <= 0x0100
    }

    /// Save the ROM to a file
    pub fn save_to_file<P: AsRef<std::path::Path>>(&self, path: P) -> Result<()> {
        let mut file = std::fs::File::create(path)?;
        file.write_all(self.data())?;
        Ok(())
    }

    /// Write a byte at a specific position without changing current position
    pub fn write_byte_at(&mut self, position: u16, byte: u8) -> Result<()> {
        self.data[position as usize] = byte;
        if position as usize >= self.size {
            self.size = position as usize + 1;
        }
        // Only extend `length` on non-zero writes
        if byte != 0 {
            self.length = self.length.max(position as usize + 1);
        }
        Ok(())
    }

    /// Advance the ROM position by a specified number of bytes without writing data
    pub fn advance_position(&mut self, bytes: usize) {
        self.position = self.position.saturating_add(bytes as u16);
        self.size = self.size.max(self.position as usize);
        // Advancing position alone doesn't change `length`
    }
}

impl Default for Rom {
    fn default() -> Self {
        Self::new()
    }
}