const std = @import("std.zig");
const builtin = @import("builtin");
const root = @import("root");
const c = std.c;

const math = std.math;
const assert = std.debug.assert;
const os = std.os;
const fs = std.fs;
const mem = std.mem;
const meta = std.meta;
const File = std.fs.File;

pub const Mode = enum {
    /// I/O operates normally, waiting for the operating system syscalls to complete.
    blocking,

    /// I/O functions are generated async and rely on a global event loop. Event-based I/O.
    evented,
};

/// The application's chosen I/O mode. This defaults to `Mode.blocking` but can be overridden
/// by `root.event_loop`.
pub const mode: Mode = if (@hasDecl(root, "io_mode"))
    root.io_mode
else if (@hasDecl(root, "event_loop"))
    Mode.evented
else
    Mode.blocking;
pub const is_async = mode != .blocking;

/// This is an enum value to use for I/O mode at runtime, since it takes up zero bytes at runtime,
/// and makes expressions comptime-known when `is_async` is `false`.
pub const ModeOverride = if (is_async) Mode else enum { blocking };
pub const default_mode: ModeOverride = if (is_async) Mode.evented else .blocking;

fn getStdOutHandle() os.fd_t {
    if (builtin.os.tag == .windows) {
        if (builtin.zig_backend == .stage2_x86_64) {
            // TODO: this is just a temporary workaround until we advance x86 backend further along.
            return os.windows.GetStdHandle(os.windows.STD_OUTPUT_HANDLE) catch os.windows.INVALID_HANDLE_VALUE;
        }
        return os.windows.peb().ProcessParameters.hStdOutput;
    }

    if (@hasDecl(root, "os") and @hasDecl(root.os, "io") and @hasDecl(root.os.io, "getStdOutHandle")) {
        return root.os.io.getStdOutHandle();
    }

    return os.STDOUT_FILENO;
}

/// TODO: async stdout on windows without a dedicated thread.
/// https://github.com/ziglang/zig/pull/4816#issuecomment-604521023
pub fn getStdOut() File {
    return File{
        .handle = getStdOutHandle(),
        .capable_io_mode = .blocking,
        .intended_io_mode = default_mode,
    };
}

fn getStdErrHandle() os.fd_t {
    if (builtin.os.tag == .windows) {
        if (builtin.zig_backend == .stage2_x86_64) {
            // TODO: this is just a temporary workaround until we advance x86 backend further along.
            return os.windows.GetStdHandle(os.windows.STD_ERROR_HANDLE) catch os.windows.INVALID_HANDLE_VALUE;
        }
        return os.windows.peb().ProcessParameters.hStdError;
    }

    if (@hasDecl(root, "os") and @hasDecl(root.os, "io") and @hasDecl(root.os.io, "getStdErrHandle")) {
        return root.os.io.getStdErrHandle();
    }

    return os.STDERR_FILENO;
}

/// This returns a `File` that is configured to block with every write, in order
/// to facilitate better debugging. This can be changed by modifying the `intended_io_mode` field.
pub fn getStdErr() File {
    return File{
        .handle = getStdErrHandle(),
        .capable_io_mode = .blocking,
        .intended_io_mode = .blocking,
    };
}

fn getStdInHandle() os.fd_t {
    if (builtin.os.tag == .windows) {
        if (builtin.zig_backend == .stage2_x86_64) {
            // TODO: this is just a temporary workaround until we advance x86 backend further along.
            return os.windows.GetStdHandle(os.windows.STD_INPUT_HANDLE) catch os.windows.INVALID_HANDLE_VALUE;
        }
        return os.windows.peb().ProcessParameters.hStdInput;
    }

    if (@hasDecl(root, "os") and @hasDecl(root.os, "io") and @hasDecl(root.os.io, "getStdInHandle")) {
        return root.os.io.getStdInHandle();
    }

    return os.STDIN_FILENO;
}

/// TODO: async stdin on windows without a dedicated thread.
/// https://github.com/ziglang/zig/pull/4816#issuecomment-604521023
pub fn getStdIn() File {
    return File{
        .handle = getStdInHandle(),
        .capable_io_mode = .blocking,
        .intended_io_mode = default_mode,
    };
}

pub const Reader = @import("io/reader.zig").Reader;
pub const Writer = @import("io/writer.zig").Writer;
pub const SeekableStream = @import("io/seekable_stream.zig").SeekableStream;

pub const BufferedWriter = @import("io/buffered_writer.zig").BufferedWriter;
pub const bufferedWriter = @import("io/buffered_writer.zig").bufferedWriter;

pub const BufferedReader = @import("io/buffered_reader.zig").BufferedReader;
pub const bufferedReader = @import("io/buffered_reader.zig").bufferedReader;

pub const PeekStream = @import("io/peek_stream.zig").PeekStream;
pub const peekStream = @import("io/peek_stream.zig").peekStream;

pub const FixedBufferStream = @import("io/fixed_buffer_stream.zig").FixedBufferStream;
pub const fixedBufferStream = @import("io/fixed_buffer_stream.zig").fixedBufferStream;

pub const CWriter = @import("io/c_writer.zig").CWriter;
pub const cWriter = @import("io/c_writer.zig").cWriter;

pub const LimitedReader = @import("io/limited_reader.zig").LimitedReader;
pub const limitedReader = @import("io/limited_reader.zig").limitedReader;

pub const CountingWriter = @import("io/counting_writer.zig").CountingWriter;
pub const countingWriter = @import("io/counting_writer.zig").countingWriter;
pub const CountingReader = @import("io/counting_reader.zig").CountingReader;
pub const countingReader = @import("io/counting_reader.zig").countingReader;

pub const MultiWriter = @import("io/multi_writer.zig").MultiWriter;
pub const multiWriter = @import("io/multi_writer.zig").multiWriter;

pub const BitReader = @import("io/bit_reader.zig").BitReader;
pub const bitReader = @import("io/bit_reader.zig").bitReader;

pub const BitWriter = @import("io/bit_writer.zig").BitWriter;
pub const bitWriter = @import("io/bit_writer.zig").bitWriter;

pub const ChangeDetectionStream = @import("io/change_detection_stream.zig").ChangeDetectionStream;
pub const changeDetectionStream = @import("io/change_detection_stream.zig").changeDetectionStream;

pub const FindByteWriter = @import("io/find_byte_writer.zig").FindByteWriter;
pub const findByteWriter = @import("io/find_byte_writer.zig").findByteWriter;

pub const FindByteOutStream = @compileError("deprecated; use `FindByteWriter`");
pub const findByteOutStream = @compileError("deprecated; use `findByteWriter`");

pub const BufferedAtomicFile = @import("io/buffered_atomic_file.zig").BufferedAtomicFile;

pub const StreamSource = @import("io/stream_source.zig").StreamSource;

/// A Writer that doesn't write to anything.
pub const null_writer = @as(NullWriter, .{ .context = {} });

const NullWriter = Writer(void, error{}, dummyWrite);
fn dummyWrite(context: void, data: []const u8) error{}!usize {
    _ = context;
    return data.len;
}

test "null_writer" {
    null_writer.writeAll("yay" ** 10) catch |err| switch (err) {};
}

test {
    _ = @import("io/bit_reader.zig");
    _ = @import("io/bit_writer.zig");
    _ = @import("io/buffered_atomic_file.zig");
    _ = @import("io/buffered_reader.zig");
    _ = @import("io/buffered_writer.zig");
    _ = @import("io/c_writer.zig");
    _ = @import("io/counting_writer.zig");
    _ = @import("io/counting_reader.zig");
    _ = @import("io/fixed_buffer_stream.zig");
    _ = @import("io/reader.zig");
    _ = @import("io/writer.zig");
    _ = @import("io/peek_stream.zig");
    _ = @import("io/seekable_stream.zig");
    _ = @import("io/stream_source.zig");
    _ = @import("io/test.zig");
}
