mp4box 0.10.0

use std::io::{Read, Seek, SeekFrom};

/// Minimal big-endian (and one little-endian) read helpers over any
/// [`Read`], replacing the `byteorder` dependency. Implemented for unsized
/// types so it works on `&mut dyn Read`.
pub trait ReadExt: Read {
    fn read_u8(&mut self) -> std::io::Result<u8> {
        let mut b = [0u8; 1];
        self.read_exact(&mut b)?;
        Ok(b[0])
    }
    fn read_u16_be(&mut self) -> std::io::Result<u16> {
        let mut b = [0u8; 2];
        self.read_exact(&mut b)?;
        Ok(u16::from_be_bytes(b))
    }
    fn read_i16_be(&mut self) -> std::io::Result<i16> {
        let mut b = [0u8; 2];
        self.read_exact(&mut b)?;
        Ok(i16::from_be_bytes(b))
    }
    fn read_u32_be(&mut self) -> std::io::Result<u32> {
        let mut b = [0u8; 4];
        self.read_exact(&mut b)?;
        Ok(u32::from_be_bytes(b))
    }
    fn read_i32_be(&mut self) -> std::io::Result<i32> {
        let mut b = [0u8; 4];
        self.read_exact(&mut b)?;
        Ok(i32::from_be_bytes(b))
    }
    fn read_u64_be(&mut self) -> std::io::Result<u64> {
        let mut b = [0u8; 8];
        self.read_exact(&mut b)?;
        Ok(u64::from_be_bytes(b))
    }
    fn read_i64_be(&mut self) -> std::io::Result<i64> {
        let mut b = [0u8; 8];
        self.read_exact(&mut b)?;
        Ok(i64::from_be_bytes(b))
    }
    /// Little-endian: the Opus `dOps` input sample rate keeps Ogg byte order.
    fn read_u32_le(&mut self) -> std::io::Result<u32> {
        let mut b = [0u8; 4];
        self.read_exact(&mut b)?;
        Ok(u32::from_le_bytes(b))
    }
}

impl<R: Read + ?Sized> ReadExt for R {}

pub fn read_slice<R: Read + Seek>(r: &mut R, offset: u64, len: u64) -> std::io::Result<Vec<u8>> {
    r.seek(SeekFrom::Start(offset))?;
    let mut v = vec![0u8; len as usize];
    r.read_exact(&mut v)?;
    Ok(v)
}

/// Decodes standard or URL-safe base64, with or without `=` padding.
/// Returns `None` on any character outside the alphabet or an impossible
/// length. Kept dependency-free for the same reason as [`ReadExt`].
pub fn base64_decode(s: &str) -> Option<Vec<u8>> {
    let mut bits: u32 = 0;
    let mut bit_count: u8 = 0;
    let mut out = Vec::with_capacity(s.len() / 4 * 3 + 3);
    let mut padded = false;
    for c in s.bytes() {
        let value = match c {
            b'A'..=b'Z' => c - b'A',
            b'a'..=b'z' => c - b'a' + 26,
            b'0'..=b'9' => c - b'0' + 52,
            b'+' | b'-' => 62,
            b'/' | b'_' => 63,
            b'=' => {
                padded = true;
                continue;
            }
            _ => return None,
        };
        // Data after padding is malformed.
        if padded {
            return None;
        }
        bits = (bits << 6) | u32::from(value);
        bit_count += 6;
        if bit_count >= 8 {
            bit_count -= 8;
            out.push((bits >> bit_count) as u8);
        }
    }
    // A trailing group of 6 bits (1 leftover char) can't encode a byte.
    if bit_count == 6 {
        return None;
    }
    Some(out)
}

pub fn hex_dump(bytes: &[u8], start_offset: u64) -> String {
    // Simple hexdump
    let mut out = String::new();
    for (i, chunk) in bytes.chunks(16).enumerate() {
        let offs = start_offset + (i as u64) * 16;
        let hexs: String = chunk.iter().map(|b| format!("{:02x} ", b)).collect();
        let ascii: String = chunk
            .iter()
            .map(|b| {
                let c = *b;
                if (32..=126).contains(&c) {
                    c as char
                } else {
                    '.'
                }
            })
            .collect();
        out.push_str(&format!("{:08x}  {:<48}  |{}|\n", offs, hexs, ascii));
    }
    out
}