// SPDX-FileCopyrightText: 2023 Joshua Goins <josh@redstrate.com>
// SPDX-License-Identifier: GPL-3.0-or-later

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

use binrw::binrw;
use binrw::{BinRead, Endian};

use crate::common::Language;
use crate::exh::{ColumnDataType, ExcelColumnDefinition, ExcelDataPagination, EXH};
use crate::ByteSpan;

#[binrw]
#[brw(magic = b"EXDF")]
#[brw(big)]
#[allow(dead_code)]
struct EXDHeader {
    version: u16,

    #[br(pad_before = 2)]
    #[br(pad_after = 20)]
    index_size: u32,
}

#[binrw]
#[brw(big)]
struct ExcelDataOffset {
    row_id: u32,
    pub offset: u32,
}

#[binrw]
#[brw(big)]
#[allow(dead_code)]
struct ExcelDataRowHeader {
    data_size: u32,
    row_count: u16,
}

#[binrw]
#[brw(big)]
#[allow(dead_code)]
pub struct EXD {
    header: EXDHeader,

    #[br(count = header.index_size / core::mem::size_of::<ExcelDataOffset>() as u32)]
    data_offsets: Vec<ExcelDataOffset>,

    #[brw(ignore)]
    pub rows: Vec<ExcelRow>,
}

#[derive(Debug)]
pub enum ColumnData {
    String(String),
    Bool(bool),
    Int8(i8),
    UInt8(u8),
    Int16(i16),
    UInt16(u16),
    Int32(i32),
    UInt32(u32),
    Float32(f32),
    Int64(i64),
    UInt64(u64),
}

pub struct ExcelRow {
    pub data: Vec<ColumnData>,
}

impl EXD {
    pub fn from_existing(exh: &EXH, buffer: ByteSpan) -> Option<EXD> {
        let mut cursor = Cursor::new(buffer);
        let mut exd = EXD::read(&mut cursor).ok()?;

        for i in 0..exh.header.row_count {
            for offset in &exd.data_offsets {
                if offset.row_id == i {
                    cursor.seek(SeekFrom::Start(offset.offset.into())).ok()?;

                    let row_header = ExcelDataRowHeader::read(&mut cursor).ok()?;

                    let header_offset = offset.offset + 6; // std::mem::size_of::<ExcelDataRowHeader>() as u32;

                    let mut read_row = |row_offset: u32| -> Option<ExcelRow> {
                        let mut subrow = ExcelRow {
                            data: Vec::with_capacity(exh.column_definitions.len()),
                        };

                        for column in &exh.column_definitions {
                            cursor
                                .seek(SeekFrom::Start((row_offset + column.offset as u32).into()))
                                .ok()?;

                            subrow.data.push(
                                Self::read_column(&mut cursor, exh, row_offset, column).unwrap(),
                            );
                        }

                        Some(subrow)
                    };

                    if row_header.row_count > 1 {
                        for i in 0..row_header.row_count {
                            let subrow_offset =
                                header_offset + (i * exh.header.data_offset + 2 * (i + 1)) as u32;

                            exd.rows.push(read_row(subrow_offset).unwrap());
                        }
                    } else {
                        exd.rows.push(read_row(header_offset).unwrap());
                    }
                }
            }
        }

        Some(exd)
    }

    fn read_data_raw<Z: BinRead<Args<'static> = ()>>(cursor: &mut Cursor<ByteSpan>) -> Option<Z> {
        Z::read_options(cursor, Endian::Big, ()).ok()
    }

    fn read_column(
        cursor: &mut Cursor<ByteSpan>,
        exh: &EXH,
        row_offset: u32,
        column: &ExcelColumnDefinition,
    ) -> Option<ColumnData> {
        let mut read_packed_bool = |shift: i32| -> bool {
            let bit = 1 << shift;
            let bool_data: i32 = Self::read_data_raw(cursor).unwrap_or(0);

            (bool_data & bit) == bit
        };

        match column.data_type {
            ColumnDataType::String => {
                let string_offset: u32 = Self::read_data_raw(cursor).unwrap();

                cursor
                    .seek(SeekFrom::Start(
                        (row_offset + exh.header.data_offset as u32 + string_offset).into(),
                    ))
                    .ok()?;

                let mut string = String::new();

                let mut byte: u8 = Self::read_data_raw(cursor).unwrap();
                while byte != 0 {
                    string.push(byte as char);
                    byte = Self::read_data_raw(cursor).unwrap();
                }

                Some(ColumnData::String(string))
            }
            ColumnDataType::Bool => {
                // FIXME: i believe Bool is int8?
                let bool_data: i32 = Self::read_data_raw(cursor).unwrap();

                Some(ColumnData::Bool(bool_data == 1))
            }
            ColumnDataType::Int8 => Some(ColumnData::Int8(Self::read_data_raw(cursor).unwrap())),
            ColumnDataType::UInt8 => Some(ColumnData::UInt8(Self::read_data_raw(cursor).unwrap())),
            ColumnDataType::Int16 => Some(ColumnData::Int16(Self::read_data_raw(cursor).unwrap())),
            ColumnDataType::UInt16 => {
                Some(ColumnData::UInt16(Self::read_data_raw(cursor).unwrap()))
            }
            ColumnDataType::Int32 => Some(ColumnData::Int32(Self::read_data_raw(cursor).unwrap())),
            ColumnDataType::UInt32 => {
                Some(ColumnData::UInt32(Self::read_data_raw(cursor).unwrap()))
            }
            ColumnDataType::Float32 => {
                Some(ColumnData::Float32(Self::read_data_raw(cursor).unwrap()))
            }
            ColumnDataType::Int64 => Some(ColumnData::Int64(Self::read_data_raw(cursor).unwrap())),
            ColumnDataType::UInt64 => {
                Some(ColumnData::UInt64(Self::read_data_raw(cursor).unwrap()))
            }
            ColumnDataType::PackedBool0 => Some(ColumnData::Bool(read_packed_bool(0))),
            ColumnDataType::PackedBool1 => Some(ColumnData::Bool(read_packed_bool(1))),
            ColumnDataType::PackedBool2 => Some(ColumnData::Bool(read_packed_bool(2))),
            ColumnDataType::PackedBool3 => Some(ColumnData::Bool(read_packed_bool(3))),
            ColumnDataType::PackedBool4 => Some(ColumnData::Bool(read_packed_bool(4))),
            ColumnDataType::PackedBool5 => Some(ColumnData::Bool(read_packed_bool(5))),
            ColumnDataType::PackedBool6 => Some(ColumnData::Bool(read_packed_bool(6))),
            ColumnDataType::PackedBool7 => Some(ColumnData::Bool(read_packed_bool(7))),
        }
    }

    pub fn calculate_filename(
        name: &str,
        language: Language,
        page: &ExcelDataPagination,
    ) -> String {
        use crate::common::get_language_code;

        match language {
            Language::None => {
                format!("{name}_{}.exd", page.start_id)
            }
            lang => {
                format!("{name}_{}_{}.exd", page.start_id, get_language_code(&lang))
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use crate::exh::EXHHeader;
    use std::fs::read;
    use std::path::PathBuf;

    use super::*;

    #[test]
    fn test_invalid() {
        let mut d = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
        d.push("resources/tests");
        d.push("random");

        let exh = EXH {
            header: EXHHeader {
                version: 0,
                data_offset: 0,
                column_count: 0,
                page_count: 0,
                language_count: 0,
                row_count: 0,
            },
            column_definitions: vec![],
            pages: vec![],
            languages: vec![],
        };

        // Feeding it invalid data should not panic
        EXD::from_existing(&exh, &read(d).unwrap());
    }
}