#![allow(dead_code)] // 测试期间未使用 runtime init 函数

#[cfg(test)]
mod tests;

use crate::ffi::OsString;
use crate::fmt;
use crate::os::windows::prelude::*;
use crate::path::PathBuf;
use crate::slice;
use crate::sys::c;
use crate::sys::windows::os::current_exe;
use crate::vec;

use core::iter;

pub fn args() -> Args {
    unsafe {
        let lp_cmd_line = c::GetCommandLineW();
        let parsed_args_list = parse_lp_cmd_line(lp_cmd_line as *const u16, || {
            current_exe().map(PathBuf::into_os_string).unwrap_or_else(|_| OsString::new())
        });

        Args { parsed_args_list: parsed_args_list.into_iter() }
    }
}

/// 实现 Windows 命令行参数解析算法。
///
/// Microsoft 的 Windows CLI 参数格式的文档可以在下面找到 <https://docs.microsoft.com/previous-versions//17w5ykft (v=vs.85)>。
///
/// Windows 在 shell32.dll 中包含一个用于执行此操作的函数，但是与该 DLL 的链接导致该进程被注册为 GUI 应用程序。
/// 即使没有绘制 windows，GUI 应用程序也会增加大量开销。请参见 <https://randomascii.wordpress.com/2018/12/03/a-not-called-function-can-cause-a-5x-slowdown/>。
///
/// 使用 <https://gist.github.com/notriddle/dde431930c392e428055b2dc22e638f5> 或 <https://paste.gg/p/anonymous/47d6ed5f5bd549168b1c69c799825223> 处提供的详尽测试套件，对该函数进行了与 Windows 10 Pro v1803 中的 shell32.dll 实现等效的测试。
///
///
///
///
///
///
unsafe fn parse_lp_cmd_line<F: Fn() -> OsString>(
    lp_cmd_line: *const u16,
    exe_name: F,
) -> Vec<OsString> {
    const BACKSLASH: u16 = '\\' as u16;
    const QUOTE: u16 = '"' as u16;
    const TAB: u16 = '\t' as u16;
    const SPACE: u16 = ' ' as u16;
    let mut ret_val = Vec::new();
    if lp_cmd_line.is_null() || *lp_cmd_line == 0 {
        ret_val.push(exe_name());
        return ret_val;
    }
    let mut cmd_line = {
        let mut end = 0;
        while *lp_cmd_line.offset(end) != 0 {
            end += 1;
        }
        slice::from_raw_parts(lp_cmd_line, end as usize)
    };
    // 开头的可执行文件名称很特殊。
    cmd_line = match cmd_line[0] {
        // 无论如何，可执行文件的名称都在下一个引号引起来。
        //
        QUOTE => {
            let args = {
                let mut cut = cmd_line[1..].splitn(2, |&c| c == QUOTE);
                if let Some(exe) = cut.next() {
                    ret_val.push(OsString::from_wide(exe));
                }
                cut.next()
            };
            if let Some(args) = args {
                args
            } else {
                return ret_val;
            }
        }
        // 实现怪癖: 当他们在此处说空白时，它们包括整个 ASCII 控制平面:
        // ` 但是，如果 lpCmdLine 以任意数量的空格开头，CommandLineToArgvW 会将第一个参数视为空字符串。
        // lpCmdLine 末尾多余的空格将被忽略。`
        //
        //
        0..=SPACE => {
            ret_val.push(OsString::new());
            &cmd_line[1..]
        }
        // 无论如何，可执行文件的名称都在下一个空格结束。
        //
        _ => {
            let args = {
                let mut cut = cmd_line.splitn(2, |&c| c > 0 && c <= SPACE);
                if let Some(exe) = cut.next() {
                    ret_val.push(OsString::from_wide(exe));
                }
                cut.next()
            };
            if let Some(args) = args {
                args
            } else {
                return ret_val;
            }
        }
    };
    let mut cur = Vec::new();
    let mut in_quotes = false;
    let mut was_in_quotes = false;
    let mut backslash_count: usize = 0;
    for &c in cmd_line {
        match c {
            // backslash
            BACKSLASH => {
                backslash_count += 1;
                was_in_quotes = false;
            }
            QUOTE if backslash_count % 2 == 0 => {
                cur.extend(iter::repeat(b'\\' as u16).take(backslash_count / 2));
                backslash_count = 0;
                if was_in_quotes {
                    cur.push('"' as u16);
                    was_in_quotes = false;
                } else {
                    was_in_quotes = in_quotes;
                    in_quotes = !in_quotes;
                }
            }
            QUOTE if backslash_count % 2 != 0 => {
                cur.extend(iter::repeat(b'\\' as u16).take(backslash_count / 2));
                backslash_count = 0;
                was_in_quotes = false;
                cur.push(b'"' as u16);
            }
            SPACE | TAB if !in_quotes => {
                cur.extend(iter::repeat(b'\\' as u16).take(backslash_count));
                if !cur.is_empty() || was_in_quotes {
                    ret_val.push(OsString::from_wide(&cur[..]));
                    cur.truncate(0);
                }
                backslash_count = 0;
                was_in_quotes = false;
            }
            _ => {
                cur.extend(iter::repeat(b'\\' as u16).take(backslash_count));
                backslash_count = 0;
                was_in_quotes = false;
                cur.push(c);
            }
        }
    }
    cur.extend(iter::repeat(b'\\' as u16).take(backslash_count));
    // 在参数列表的末尾包含带引号的空字符串
    if !cur.is_empty() || was_in_quotes || in_quotes {
        ret_val.push(OsString::from_wide(&cur[..]));
    }
    ret_val
}

pub struct Args {
    parsed_args_list: vec::IntoIter<OsString>,
}

impl fmt::Debug for Args {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        self.parsed_args_list.as_slice().fmt(f)
    }
}

impl Iterator for Args {
    type Item = OsString;
    fn next(&mut self) -> Option<OsString> {
        self.parsed_args_list.next()
    }
    fn size_hint(&self) -> (usize, Option<usize>) {
        self.parsed_args_list.size_hint()
    }
}

impl DoubleEndedIterator for Args {
    fn next_back(&mut self) -> Option<OsString> {
        self.parsed_args_list.next_back()
    }
}

impl ExactSizeIterator for Args {
    fn len(&self) -> usize {
        self.parsed_args_list.len()
    }
}