import os

const tfolder = os.join_path(os.vtmp_dir(), 'v', 'tests', 'os_file_test')

const tfile = os.join_path_single(tfolder, 'test_file')

fn testsuite_begin() {
    os.rmdir_all(tfolder) or {}
    assert !os.is_dir(tfolder)
    os.mkdir_all(tfolder)!
    os.chdir(tfolder)!
    assert os.is_dir(tfolder)
}

fn testsuite_end() {
    os.rmdir_all(tfolder) or {}
}

struct Point {
    x f64
    y f64
    z f64
}

struct Extended_Point {
    a f64
    b f64
    c f64
    d f64
    e f64
    f f64
    g f64
    h f64
    i f64
}

enum Color {
    red
    green
    blue
}

[flag]
enum Permissions {
    read
    write
    execute
}

const (
    unit_point         = Point{1.0, 1.0, 1.0}
    another_point      = Point{0.25, 2.25, 6.25}
    extended_point     = Extended_Point{1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0}
    another_byte       = u8(123)
    another_color      = Color.red
    another_permission = Permissions.read | .write
)

// test_read_bytes_into_newline_text tests reading text from a file with newlines.
// This test simulates reading a larger text file step by step into a buffer and
// returning on each newline, even before the buffer is full, and reaching EOF before
// the buffer is completely filled.
fn test_read_bytes_into_newline_text() {
    mut f := os.open_file(tfile, 'w')!
    f.write_string('Hello World!\nGood\r morning.')!
    f.close()

    f = os.open_file(tfile, 'r')!
    mut buf := []u8{len: 8}

    n0 := f.read_bytes_into_newline(mut buf)!
    assert n0 == 8

    n1 := f.read_bytes_into_newline(mut buf)!
    assert n1 == 5

    n2 := f.read_bytes_into_newline(mut buf)!
    assert n2 == 8

    n3 := f.read_bytes_into_newline(mut buf)!
    assert n3 == 6

    f.close()
}

// test_read_bytes_into_newline_binary tests reading a binary file with NUL bytes.
// This test simulates the scenario when a byte stream is read and a newline byte
// appears in that stream and an EOF occurs before the buffer is full.
fn test_read_bytes_into_newline_binary() {
    os.rm(tfile) or {} // FIXME This is a workaround for macos, because the file isn't truncated when open with 'w'
    mut bw := []u8{len: 15}
    bw[9] = 0xff
    bw[12] = 10 // newline

    n0_bytes := bw[0..10]
    n1_bytes := bw[10..13]
    n2_bytes := bw[13..]

    mut f := os.open_file(tfile, 'w')!
    f.write(bw)!
    f.close()

    f = os.open_file(tfile, 'r')!
    mut buf := []u8{len: 10}

    n0 := f.read_bytes_into_newline(mut buf)!
    assert n0 == 10
    assert buf[..n0] == n0_bytes

    n1 := f.read_bytes_into_newline(mut buf)!
    assert n1 == 3
    assert buf[..n1] == n1_bytes

    n2 := f.read_bytes_into_newline(mut buf)!
    assert n2 == 2
    assert buf[..n2] == n2_bytes
    f.close()
}

// test_read_eof_last_read_partial_buffer_fill tests that when reading a file
// the end-of-file is detected and results in a none error being returned. This
// test simulates file reading where the end-of-file is reached inside an fread
// containing data.
fn test_read_eof_last_read_partial_buffer_fill() {
    mut f := os.open_file(tfile, 'w')!
    bw := []u8{len: 199, init: 5}
    f.write(bw)!
    f.close()

    f = os.open_file(tfile, 'r')!
    mut br := []u8{len: 100}
    // Read first 100 bytes of 199 byte file, should fill buffer with no error.
    n0 := f.read(mut br)!
    assert n0 == 100
    // Read remaining 99 bytes of 199 byte file, should fill buffer with no
    // error, even though end-of-file was reached.
    n1 := f.read(mut br)!
    assert n1 == 99
    // Read again, end-of-file was previously reached so should return none
    // error.
    if _ := f.read(mut br) {
        // This is not intended behavior because the read function should
        // not return a number of bytes read when end-of-file is reached.
        assert false
    } else {
        // Expected an error when received end-of-file.
        assert err is os.Eof
    }
    f.close()
}

// test_read_eof_last_read_full_buffer_fill tests that when reading a file the
// end-of-file is detected and results in a none error being returned. This test
// simulates file reading where the end-of-file is reached at the beinning of an
// fread that returns no data.
fn test_read_eof_last_read_full_buffer_fill() {
    mut f := os.open_file(tfile, 'w')!
    bw := []u8{len: 200, init: 5}
    f.write(bw)!
    f.close()

    f = os.open_file(tfile, 'r')!
    mut br := []u8{len: 100}
    // Read first 100 bytes of 200 byte file, should fill buffer with no error.
    n0 := f.read(mut br)!
    assert n0 == 100
    // Read remaining 100 bytes of 200 byte file, should fill buffer with no
    // error. The end-of-file isn't reached yet, but there is no more data.
    n1 := f.read(mut br)!
    assert n1 == 100
    // Read again, end-of-file was previously reached so should return none
    // error.
    if _ := f.read(mut br) {
        // This is not intended behavior because the read function should
        // not return a number of bytes read when end-of-file is reached.
        assert false
    } else {
        // Expect an error at EOF.
        assert err is os.Eof
    }
    f.close()
}

fn test_write_struct() {
    os.rm(tfile) or {} // FIXME This is a workaround for macos, because the file isn't truncated when open with 'w'
    size_of_point := int(sizeof(Point))
    mut f := os.open_file(tfile, 'w')!
    f.write_struct(another_point)!
    f.close()
    x := os.read_file(tfile)!
    pcopy := unsafe { &u8(memdup(&another_point, size_of_point)) }
    y := unsafe { pcopy.vstring_with_len(size_of_point) }
    assert x == y
    $if debug {
        eprintln(x.bytes())
        eprintln(y.bytes())
    }
}

fn test_write_struct_at() {
    mut f := os.open_file(tfile, 'w')!
    f.write_struct(extended_point)!
    f.write_struct_at(another_point, 3)!
    f.close()
    f = os.open_file(tfile, 'r')!
    mut p := Point{}
    f.read_struct_at(mut p, 3)!
    f.close()

    assert p == another_point
}

fn test_read_struct() {
    mut f := os.open_file(tfile, 'w')!
    f.write_struct(another_point)!
    f.close()

    f = os.open_file(tfile, 'r')!
    mut p := Point{}
    f.read_struct(mut p)!
    f.close()

    assert p == another_point
}

fn test_read_struct_at() {
    mut f := os.open_file(tfile, 'w')!
    f.write([u8(1), 2, 3])!
    f.write_struct(another_point)!
    f.close()
    f = os.open_file(tfile, 'r')!
    mut p := Point{}
    f.read_struct_at(mut p, 3)!
    f.close()

    assert p == another_point
}

fn test_write_raw() {
    os.rm(tfile) or {} // FIXME This is a workaround for macos, because the file isn't truncated when open with 'w'
    size_of_point := int(sizeof(Point))
    mut f := os.open_file(tfile, 'w')!
    f.write_raw(another_point)!
    f.close()
    x := os.read_file(tfile)!
    pcopy := unsafe { &u8(memdup(&another_point, size_of_point)) }
    y := unsafe { pcopy.vstring_with_len(size_of_point) }
    assert x == y
    $if debug {
        eprintln(x.bytes())
        eprintln(y.bytes())
    }
}

fn test_write_raw_at() {
    mut f := os.open_file(tfile, 'w')!
    f.write_raw(extended_point)!
    f.write_raw_at(another_point, 3)!
    f.close()
    f = os.open_file(tfile, 'r')!
    mut p := Point{}
    f.read_struct_at(mut p, 3)!
    f.close()

    assert p == another_point
}

fn test_write_raw_at_negative_pos() {
    mut f := os.open_file(tfile, 'w')!
    if _ := f.write_raw_at(another_point, u64(-1)) {
        assert false
    }
    f.write_raw_at(another_point, u64(-1)) or { assert err.msg() == 'Invalid argument' }
    f.close()
}

fn test_read_raw() {
    mut f := os.open_file(tfile, 'w')!
    f.write_raw(another_point)!
    f.write_raw(another_byte)!
    f.write_raw(another_color)!
    f.write_raw(another_permission)!
    f.close()
    f = os.open_file(tfile, 'r')!
    p := f.read_raw[Point]()!
    b := f.read_raw[u8]()!
    c := f.read_raw[Color]()!
    x := f.read_raw[Permissions]()!
    f.close()

    assert p == another_point
    assert b == another_byte
    assert c == another_color
    assert x == another_permission
}

fn test_read_raw_at() {
    mut f := os.open_file(tfile, 'w')!
    f.write([u8(1), 2, 3])!
    f.write_raw(another_point)!
    f.write_raw(another_byte)!
    f.write_raw(another_color)!
    f.write_raw(another_permission)!
    f.close()
    f = os.open_file(tfile, 'r')!
    mut at := u64(3)
    p := f.read_raw_at[Point](at)!
    at += sizeof(Point)
    b := f.read_raw_at[u8](at)!
    at += sizeof(u8)
    c := f.read_raw_at[Color](at)!
    at += sizeof(Color)
    x := f.read_raw_at[Permissions](at)!
    at += sizeof(Permissions)
    f.close()

    assert p == another_point
    assert b == another_byte
    assert c == another_color
    assert x == another_permission
}

fn test_read_raw_at_negative_pos() {
    mut f := os.open_file(tfile, 'r')!
    if _ := f.read_raw_at[Point](u64(-1)) {
        assert false
    }
    f.read_raw_at[Point](u64(-1)) or { assert err.msg() == 'Invalid argument' }
    f.close()
}

fn test_seek() {
    mut f := os.open_file(tfile, 'w')!
    f.write_raw(another_point)!
    f.write_raw(another_byte)!
    f.write_raw(another_color)!
    f.write_raw(another_permission)!
    f.close()

    // println('> ${sizeof(Point)} ${sizeof(byte)} ${sizeof(Color)} ${sizeof(Permissions)}')
    f = os.open_file(tfile, 'r')!
    //
    f.seek(i64(sizeof(Point)), .start)!
    assert f.tell()! == sizeof(Point)
    b := f.read_raw[u8]()!
    assert b == another_byte

    f.seek(i64(sizeof(Color)), .current)!
    x := f.read_raw[Permissions]()!
    assert x == another_permission
    //
    f.close()
}

fn test_tell() {
    for size in 10 .. 30 {
        s := 'x'.repeat(size)
        os.write_file(tfile, s)!
        fs := os.file_size(tfile)
        assert int(fs) == size
        //
        mut f := os.open_file(tfile, 'r')!
        f.seek(-5, .end)!
        pos := f.tell()!
        f.close()
        // dump(pos)
        assert pos == size - 5
    }
}

fn test_reopen() {
    tfile1 := os.join_path_single(tfolder, 'tfile1')
    tfile2 := os.join_path_single(tfolder, 'tfile2')
    os.write_file(tfile1, 'Hello World!\nGood\r morning.\nBye 1.')!
    os.write_file(tfile2, 'Another file\nAnother line.\nBye 2.')!
    assert os.file_size(tfile1) > 0
    assert os.file_size(tfile2) > 0

    mut line_buffer := []u8{len: 1024}

    mut f2 := os.open(tfile2)!
    x := f2.read_bytes_into_newline(mut line_buffer)!
    assert !f2.eof()
    assert x > 0
    assert line_buffer#[..x].bytestr() == 'Another file\n'

    // Note: after this call, f2 should be using the file `tfile1`:
    f2.reopen(tfile1, 'r')!
    assert !f2.eof()

    z := f2.read(mut line_buffer) or { panic(err) }
    assert f2.eof()
    assert z > 0
    content := line_buffer#[..z].bytestr()
    // dump(content)
    assert content.starts_with('Hello World')
    assert content.ends_with('Bye 1.')
}

fn test_eof() {
    os.write_file(tfile, 'Hello World!\n')!

    mut f := os.open(tfile)!
    f.read_bytes(10)
    assert !f.eof()
    f.read_bytes(100)
    assert f.eof()
    f.close()
}

fn test_open_file_wb_ab() {
    os.rm(tfile) or {}
    mut wfile := os.open_file('text.txt', 'wb', 0o666)!
    wfile.write_string('hello')!
    wfile.close()
    assert os.read_file('text.txt')! == 'hello'
    //
    mut afile := os.open_file('text.txt', 'ab', 0o666)!
    afile.write_string('hello')!
    afile.close()
    assert os.read_file('text.txt')! == 'hellohello'
}

fn test_open_append() {
    os.rm(tfile) or {}
    mut f1 := os.open_append(tfile)!
    f1.write_string('abc\n')!
    f1.close()
    assert os.read_lines(tfile)! == ['abc']
    //
    mut f2 := os.open_append(tfile)!
    f2.write_string('abc\n')!
    f2.close()
    assert os.read_lines(tfile)! == ['abc', 'abc']
    //
    mut f3 := os.open_append(tfile)!
    f3.write_string('def\n')!
    f3.close()
    assert os.read_lines(tfile)! == ['abc', 'abc', 'def']
}

fn test_open_file_on_chinese_windows() {
    $if windows {
        os.rm('中文.txt') or {}
        mut f1 := os.open_file('中文.txt', 'w+', 0x666) or { panic(err) }
        f1.write_string('test')!
        f1.close()

        assert os.read_file('中文.txt')! == 'test'
        assert os.file_size('中文.txt') == 4

        os.truncate('中文.txt', 2)!
        assert os.file_size('中文.txt') == 2
    }
}