use crate::deflate::deflate;

pub struct Entry {
    pub name: String,
    stored: Vec<u8>,
    uncompressed_size: u32,
    method: u16,
    offset: u32,
    crc: u32,
}

pub struct Zip {
    entries: Vec<Entry>,
}

impl Zip {
    pub fn new() -> Self {
        Zip { entries: Vec::new() }
    }

    pub fn add(&mut self, name: &str, data: Vec<u8>) {
        let crc = crc32(&data);
        let size = data.len() as u32;
        self.entries.push(Entry {
            name: name.to_string(),
            stored: data,
            uncompressed_size: size,
            method: 0,
            offset: 0,
            crc,
        });
    }

    pub fn add_deflated(&mut self, name: &str, data: Vec<u8>) {
        let crc = crc32(&data);
        let uncompressed_size = data.len() as u32;
        let compressed = deflate(&data);
        if compressed.len() < data.len() {
            self.entries.push(Entry {
                name: name.to_string(),
                stored: compressed,
                uncompressed_size,
                method: 8,
                offset: 0,
                crc,
            });
        } else {
            self.add(name, data);
        }
    }

    pub fn finish(mut self) -> Vec<u8> {
        let mut out = Vec::new();

        for e in self.entries.iter_mut() {
            e.offset = out.len() as u32;
            write_local_header(&mut out, e);
            out.extend_from_slice(&e.stored);
        }

        let cd_start = out.len() as u32;
        for e in &self.entries {
            write_central_header(&mut out, e);
        }
        let cd_size = out.len() as u32 - cd_start;

        write_eocd(&mut out, self.entries.len() as u16, cd_size, cd_start);

        out
    }
}

fn write_local_header(out: &mut Vec<u8>, e: &Entry) {
    out.extend_from_slice(&0x0403_4b50u32.to_le_bytes());
    out.extend_from_slice(&20u16.to_le_bytes());
    out.extend_from_slice(&0u16.to_le_bytes());
    out.extend_from_slice(&e.method.to_le_bytes());
    out.extend_from_slice(&0u16.to_le_bytes());
    out.extend_from_slice(&0x21u16.to_le_bytes());
    out.extend_from_slice(&e.crc.to_le_bytes());
    out.extend_from_slice(&(e.stored.len() as u32).to_le_bytes());
    out.extend_from_slice(&e.uncompressed_size.to_le_bytes());
    out.extend_from_slice(&(e.name.len() as u16).to_le_bytes());
    out.extend_from_slice(&0u16.to_le_bytes());
    out.extend_from_slice(e.name.as_bytes());
}

fn write_central_header(out: &mut Vec<u8>, e: &Entry) {
    out.extend_from_slice(&0x0201_4b50u32.to_le_bytes());
    out.extend_from_slice(&20u16.to_le_bytes());
    out.extend_from_slice(&20u16.to_le_bytes());
    out.extend_from_slice(&0u16.to_le_bytes());
    out.extend_from_slice(&e.method.to_le_bytes());
    out.extend_from_slice(&0u16.to_le_bytes());
    out.extend_from_slice(&0x21u16.to_le_bytes());
    out.extend_from_slice(&e.crc.to_le_bytes());
    out.extend_from_slice(&(e.stored.len() as u32).to_le_bytes());
    out.extend_from_slice(&e.uncompressed_size.to_le_bytes());
    out.extend_from_slice(&(e.name.len() as u16).to_le_bytes());
    out.extend_from_slice(&0u16.to_le_bytes());
    out.extend_from_slice(&0u16.to_le_bytes());
    out.extend_from_slice(&0u16.to_le_bytes());
    out.extend_from_slice(&0u16.to_le_bytes());
    out.extend_from_slice(&0u32.to_le_bytes());
    out.extend_from_slice(&e.offset.to_le_bytes());
    out.extend_from_slice(e.name.as_bytes());
}

fn write_eocd(out: &mut Vec<u8>, count: u16, cd_size: u32, cd_offset: u32) {
    out.extend_from_slice(&0x0605_4b50u32.to_le_bytes());
    out.extend_from_slice(&0u16.to_le_bytes());
    out.extend_from_slice(&0u16.to_le_bytes());
    out.extend_from_slice(&count.to_le_bytes());
    out.extend_from_slice(&count.to_le_bytes());
    out.extend_from_slice(&cd_size.to_le_bytes());
    out.extend_from_slice(&cd_offset.to_le_bytes());
    out.extend_from_slice(&0u16.to_le_bytes());
}

pub fn crc32(data: &[u8]) -> u32 {
    let mut crc: u32 = 0xFFFF_FFFF;
    for &b in data {
        crc ^= b as u32;
        for _ in 0..8 {
            let mask = (crc & 1).wrapping_neg();
            crc = (crc >> 1) ^ (0xEDB8_8320 & mask);
        }
    }
    !crc
}