use crate::helper::{AlignExt, ReadExt};
use anyhow::{Result, anyhow, bail};
use humansize::DECIMAL;
use log::{debug, info};
use std::io::{Cursor, Read, Seek, SeekFrom};

#[derive(Debug, Clone)]
pub struct NodeInfo {
    pub name: String,
    pub size: u64,
    pub(super) offset: u64,
    _status: u32,
}

pub struct BlockInfo {
    pub comp_size: u32,
    pub decomp_size: u32,
    pub comp_scheme: CompressionScheme,
}

pub struct UnityFSHeader {
    pub(crate) nodes: Vec<NodeInfo>,
    pub file_version: u32,
    pub player_version: String,
    pub unity_version: String,
}

impl UnityFSHeader {
    pub fn read(mut file: impl Read + Seek) -> Result<(Self, Vec<BlockInfo>)> {
        let signature = file.read_cstr()?;
        if signature.as_str() != "UnityFS" {
            bail!("unknown signature {signature:?}")
        }

        let file_version = file.read_u32_be()?;
        let player_version = file.read_cstr()?;
        let unity_version = file.read_cstr()?;
        let size = file.read_u64_be()?;
        let blockindex_comp_size = file.read_u32_be()?;
        let blockindex_decomp_size = file.read_u32_be()?;
        let flags = file.read_u32_be()?;

        let meta_comp_scheme = CompressionScheme::from_flag_num(flags as u8).ok_or(anyhow!(
            "unknown block compression 0x{:02x}",
            (flags & 0x3f) as u8
        ))?;
        let blockindex_eof = flags & 0x80 != 0;
        let blockindex_has_directory = flags & 0x40 != 0;
        let blockindex_need_padding = flags & 0x200 != 0;

        info!("File Version: {file_version:?}");
        info!("Player Version: {player_version:?}");
        info!("Unity Version: {unity_version:?}");
        debug!("size={size:?}");
        debug!("meta_comp_size={blockindex_comp_size:?}");
        debug!("meta_decomp_size={blockindex_decomp_size:?}");
        debug!("flags={flags:?}");
        debug!("meta_comp_scheme={meta_comp_scheme:?}");
        debug!("blockindex_eof={blockindex_eof:?}");
        debug!("blockindex_has_directory={blockindex_has_directory:?}");
        debug!("blockindex_need_padding={blockindex_need_padding:?}");

        let mut blockindex = {
            let restore_position = if blockindex_eof {
                let pos = file.stream_position()?;
                file.seek(SeekFrom::End(-(blockindex_comp_size as i64)))?;
                Some(pos)
            } else {
                None
            };

            let mut blockindex = vec![0u8; blockindex_comp_size as usize];
            file.read_exact(&mut blockindex)?;

            if let Some(pos) = restore_position {
                file.seek(SeekFrom::Start(pos))?;
            }
            let blockindex =
                meta_comp_scheme.decompress(blockindex, blockindex_decomp_size as usize)?;
            Cursor::new(blockindex)
        };

        file.align(16)?;

        blockindex.read_u128_be()?;

        let num_blocks = blockindex.read_u32_be()?;
        info!("File has {num_blocks} blocks");
        let mut blocks = Vec::new();
        for _ in 0..num_blocks {
            let decomp_size = blockindex.read_u32_be()?;
            let comp_size = blockindex.read_u32_be()?;
            let flags = blockindex.read_u16_be()?;
            let comp_scheme = CompressionScheme::from_flag_num(flags as u8)
                .ok_or(anyhow!("unknown block compression 0x{:02x}", flags & 0x3f))?;
            blocks.push(BlockInfo {
                comp_size,
                decomp_size,
                comp_scheme,
            })
        }

        let num_nodes = blockindex.read_u32_be()?;
        debug!("num_nodes={num_nodes:?}");
        let mut nodes = Vec::new();
        for _ in 0..num_nodes {
            let offset = blockindex.read_u64_be()?;
            let size = blockindex.read_u64_be()?;
            let status = blockindex.read_u32_be()?;
            let name = blockindex.read_cstr()?;
            info!(
                "found node {name:?} (size={}, status={status})",
                humansize::format_size(size, DECIMAL)
            );
            nodes.push(NodeInfo {
                offset,
                size,
                _status: status,
                name,
            })
        }

        Ok((
            Self {
                file_version,
                player_version,
                unity_version,
                nodes,
            },
            blocks,
        ))
    }
    pub fn nodes(&self) -> &[NodeInfo] {
        &self.nodes
    }
}

#[derive(Debug, Clone, Copy, PartialEq)]
pub enum CompressionScheme {
    None,
    Lzma,
    Lz4,
    Lz4hc,
    Lzham,
}
impl CompressionScheme {
    pub fn from_flag_num(n: u8) -> Option<CompressionScheme> {
        Some(match n & 0x3f {
            0 => CompressionScheme::None,
            1 => CompressionScheme::Lzma,
            2 => CompressionScheme::Lz4,
            3 => CompressionScheme::Lz4hc,
            4 => CompressionScheme::Lzham,
            _ => return None,
        })
    }
    pub fn decompress(&self, block: Vec<u8>, decomp_size: usize) -> Result<Vec<u8>> {
        match self {
            CompressionScheme::None => Ok(block),
            CompressionScheme::Lzma => {
                let mut r = lzma::Reader::from(Cursor::new(block))?;
                let mut buf = Vec::new();
                r.read_to_end(&mut buf)?;
                Ok(buf)
            }
            CompressionScheme::Lz4hc | CompressionScheme::Lz4 => {
                Ok(lz4_flex::block::decompress(&block, decomp_size)?)
            }
            // CompressionScheme::LZ4HC | CompressionScheme::LZ4 => {
            //     Ok(lz4::block::decompress(&block, Some(decomp_size as i32))?)
            // }
            CompressionScheme::Lzham => todo!(),
        }
    }
}