unity-solution-generator 0.1.1

use std::fs::{File, OpenOptions};
use std::io::{Read, Write};
use std::path::Path;

use crate::error::{Result, io_err};

pub fn read_file(path: &str) -> Result<String> {
    let mut f = File::open(path).map_err(|e| io_err(path, e))?;
    let mut s = String::new();
    f.read_to_string(&mut s).map_err(|e| io_err(path, e))?;
    Ok(s)
}

/// Read a file as bytes; used for byte-equality fast path in `write_file_if_changed`.
fn read_bytes(path: &str) -> std::io::Result<Vec<u8>> {
    let mut f = File::open(path)?;
    let mut buf = Vec::new();
    f.read_to_end(&mut buf)?;
    Ok(buf)
}

/// Returns true if the file was written, false if it was already byte-identical.
pub fn write_file_if_changed(path: &str, content: &str) -> Result<bool> {
    let bytes = content.as_bytes();
    if let Ok(existing) = read_bytes(path) {
        if existing.as_slice() == bytes {
            return Ok(false);
        }
    }
    let mut f = OpenOptions::new()
        .create(true)
        .write(true)
        .truncate(true)
        .open(path)
        .map_err(|e| io_err(path, e))?;
    f.write_all(bytes).map_err(|e| io_err(path, e))?;
    Ok(true)
}

pub fn create_dir_all(path: &str) {
    let _ = std::fs::create_dir_all(path);
}

pub fn file_exists(path: &str) -> bool {
    Path::new(path).exists()
}

pub fn is_dir(path: &str) -> bool {
    std::fs::metadata(path).map(|m| m.is_dir()).unwrap_or(false)
}

/// Look for a `# version: N` line near the top of a cache file and return
/// `true` if it parses to exactly `expected`. Older caches without the line,
/// caches with a newer/older `N`, and malformed lines all return `false` so
/// the caller can silently regenerate. Stops scanning at the first non-comment
/// line to keep the cost bounded.
pub fn has_matching_version(content: &str, expected: u32) -> bool {
    for line in content.split('\n') {
        if line.is_empty() {
            continue;
        }
        if !line.starts_with('#') {
            // Reached cache body without finding a version line.
            return false;
        }
        if let Some(rest) = line.strip_prefix("# version:") {
            return rest.trim().parse::<u32>().ok() == Some(expected);
        }
    }
    false
}

/// Plain `readdir` returning names (excluding `.` and `..`). Order undefined.
pub fn list_directory(path: &str) -> Vec<String> {
    let Ok(rd) = std::fs::read_dir(path) else {
        return Vec::new();
    };
    rd.filter_map(|e| e.ok().map(|e| e.file_name().to_string_lossy().into_owned()))
        .collect()
}