extern crate regex;
extern crate version_check;

use regex::Regex;
use std::collections::HashMap;
use std::env;
use std::fmt;
use std::process::Command;
use version_check::{is_min_date, is_min_version, supports_features};

// Specifies the minimum nightly version needed to compile pyo3.
const MIN_DATE: &'static str = "2018-05-01";
const MIN_VERSION: &'static str = "1.27.0-nightly";

#[derive(Debug)]
struct PythonVersion {
    major: u8,
    // minor == None means any minor version will do
    minor: Option<u8>,
}

impl PartialEq for PythonVersion {
    fn eq(&self, o: &PythonVersion) -> bool {
        self.major == o.major && (self.minor.is_none() || self.minor == o.minor)
    }
}

impl fmt::Display for PythonVersion {
    fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
        self.major.fmt(f)?;
        f.write_str(".")?;
        match self.minor {
            Some(minor) => minor.fmt(f)?,
            None => f.write_str("*")?,
        };
        Ok(())
    }
}

const PY3_MIN_MINOR: u8 = 5;

const CFG_KEY: &'static str = "py_sys_config";

// A list of python interpreter compile-time preprocessor defines that
// we will pick up and pass to rustc via --cfg=py_sys_config={varname};
// this allows using them conditional cfg attributes in the .rs files, so
//
// #[cfg(py_sys_config="{varname}"]
//
// is the equivalent of #ifdef {varname} name in C.
//
// see Misc/SpecialBuilds.txt in the python source for what these mean.
//
// (hrm, this is sort of re-implementing what distutils does, except
// by passing command line args instead of referring to a python.h)
#[cfg(not(target_os = "windows"))]
static SYSCONFIG_FLAGS: [&'static str; 7] = [
    "Py_USING_UNICODE",
    "Py_UNICODE_WIDE",
    "WITH_THREAD",
    "Py_DEBUG",
    "Py_REF_DEBUG",
    "Py_TRACE_REFS",
    "COUNT_ALLOCS",
];

static SYSCONFIG_VALUES: [&'static str; 1] = [
    // cfg doesn't support flags with values, just bools - so flags
    // below are translated into bools as {varname}_{val}
    //
    // for example, Py_UNICODE_SIZE_2 or Py_UNICODE_SIZE_4
    "Py_UNICODE_SIZE", // note - not present on python 3.3+, which is always wide
];

/// Examine python's compile flags to pass to cfg by launching
/// the interpreter and printing variables of interest from
/// sysconfig.get_config_vars.
#[cfg(not(target_os = "windows"))]
fn get_config_vars(python_path: &String) -> Result<HashMap<String, String>, String> {
    let mut script = "import sysconfig; \
                      config = sysconfig.get_config_vars();"
        .to_owned();

    for k in SYSCONFIG_FLAGS.iter().chain(SYSCONFIG_VALUES.iter()) {
        script.push_str(&format!(
            "print(config.get('{}', {}));",
            k,
            if is_value(k) { "None" } else { "0" }
        ));
    }

    let stdout = run_python_script(python_path, &script)?;
    let split_stdout: Vec<&str> = stdout.trim_right().lines().collect();
    if split_stdout.len() != SYSCONFIG_VALUES.len() + SYSCONFIG_FLAGS.len() {
        return Err(format!(
            "python stdout len didn't return expected number of lines: {}",
            split_stdout.len()
        ));
    }
    let all_vars = SYSCONFIG_FLAGS.iter().chain(SYSCONFIG_VALUES.iter());
    let mut all_vars = all_vars.zip(split_stdout.iter()).fold(
        HashMap::new(),
        |mut memo: HashMap<String, String>, (&k, &v)| {
            if !(v.to_owned() == "None" && is_value(k)) {
                memo.insert(k.to_owned(), v.to_owned());
            }
            memo
        },
    );

    let debug = Some(&"1".to_string()) == all_vars.get("Py_DEBUG");
    if debug {
        all_vars.insert("Py_REF_DEBUG".to_owned(), "1".to_owned());
        all_vars.insert("Py_TRACE_REFS".to_owned(), "1".to_owned());
        all_vars.insert("COUNT_ALLOCS".to_owned(), "1".to_owned());
    }

    Ok(all_vars)
}

#[cfg(target_os = "windows")]
fn get_config_vars(_: &String) -> Result<HashMap<String, String>, String> {
    // sysconfig is missing all the flags on windows, so we can't actually
    // query the interpreter directly for its build flags.
    //
    // For the time being, this is the flags as defined in the python source's
    // PC\pyconfig.h. This won't work correctly if someone has built their
    // python with a modified pyconfig.h - sorry if that is you, you will have
    // to comment/uncomment the lines below.
    let mut map: HashMap<String, String> = HashMap::new();
    map.insert("Py_USING_UNICODE".to_owned(), "1".to_owned());
    map.insert("Py_UNICODE_WIDE".to_owned(), "0".to_owned());
    map.insert("WITH_THREAD".to_owned(), "1".to_owned());
    map.insert("Py_UNICODE_SIZE".to_owned(), "2".to_owned());

    // This is defined #ifdef _DEBUG. The visual studio build seems to produce
    // a specially named pythonXX_d.exe and pythonXX_d.dll when you build the
    // Debug configuration, which this script doesn't currently support anyway.
    // map.insert("Py_DEBUG", "1");

    // Uncomment these manually if your python was built with these and you want
    // the cfg flags to be set in rust.
    //
    // map.insert("Py_REF_DEBUG", "1");
    // map.insert("Py_TRACE_REFS", "1");
    // map.insert("COUNT_ALLOCS", 1");
    Ok(map)
}

fn is_value(key: &str) -> bool {
    SYSCONFIG_VALUES.iter().find(|x| **x == key).is_some()
}

fn cfg_line_for_var(key: &str, val: &str) -> Option<String> {
    if is_value(key) {
        // is a value; suffix the key name with the value
        Some(format!("cargo:rustc-cfg={}=\"{}_{}\"\n", CFG_KEY, key, val))
    } else if val != "0" {
        // is a flag that isn't zero
        Some(format!("cargo:rustc-cfg={}=\"{}\"", CFG_KEY, key))
    } else {
        // is a flag that is zero
        None
    }
}

/// Run a python script using the specified interpreter binary.
fn run_python_script(interpreter: &str, script: &str) -> Result<String, String> {
    let out = Command::new(interpreter)
        .args(&["-c", script])
        .output()
        .map_err(|e| format!("failed to run python interpreter:\n\n{}", e))?;

    if !out.status.success() {
        let stderr = String::from_utf8(out.stderr).unwrap();
        return Err(format!("python script failed with stderr:\n\n{}", stderr));
    }

    Ok(String::from_utf8(out.stdout).unwrap())
}

#[cfg(not(target_os = "macos"))]
#[cfg(not(target_os = "windows"))]
fn get_rustc_link_lib(
    _: &PythonVersion,
    ld_version: &str,
    enable_shared: bool,
) -> Result<String, String> {
    if enable_shared {
        Ok(format!("cargo:rustc-link-lib=python{}", ld_version))
    } else {
        Ok(format!("cargo:rustc-link-lib=static=python{}", ld_version))
    }
}

#[cfg(target_os = "macos")]
fn get_macos_linkmodel() -> Result<String, String> {
    let script = "import sysconfig;\
    print('framework' if sysconfig.get_config_var('PYTHONFRAMEWORK') else ('shared' if sysconfig.get_config_var('Py_ENABLE_SHARED') else 'static'));";
    let out = run_python_script("python", script).unwrap();
    Ok(out.trim_right().to_owned())
}

#[cfg(target_os = "macos")]
fn get_rustc_link_lib(_: &PythonVersion, ld_version: &str, _: bool) -> Result<String, String> {
    // os x can be linked to a framework or static or dynamic, and
    // Py_ENABLE_SHARED is wrong; framework means shared library
    match get_macos_linkmodel().unwrap().as_ref() {
        "static" => Ok(format!("cargo:rustc-link-lib=static=python{}", ld_version)),
        "shared" => Ok(format!("cargo:rustc-link-lib=python{}", ld_version)),
        "framework" => Ok(format!("cargo:rustc-link-lib=python{}", ld_version)),
        other => Err(format!("unknown linkmodel {}", other)),
    }
}

/// Parse string as interpreter version.
fn get_interpreter_version(line: &str) -> Result<PythonVersion, String> {
    let version_re = Regex::new(r"\((\d+), (\d+)\)").unwrap();
    match version_re.captures(&line) {
        Some(cap) => Ok(PythonVersion {
            major: cap.get(1).unwrap().as_str().parse().unwrap(),
            minor: Some(cap.get(2).unwrap().as_str().parse().unwrap()),
        }),
        None => Err(format!("Unexpected response to version query {}", line)),
    }
}

#[cfg(target_os = "windows")]
fn get_rustc_link_lib(version: &PythonVersion, _: &str, _: bool) -> Result<String, String> {
    // Py_ENABLE_SHARED doesn't seem to be present on windows.
    Ok(format!(
        "cargo:rustc-link-lib=pythonXY:python{}{}",
        version.major,
        match version.minor {
            Some(minor) => minor.to_string(),
            None => "".to_owned(),
        }
    ))
}

/// Locate a suitable python interpreter and extract config from it.
/// If the environment variable `PYTHON_SYS_EXECUTABLE`, use the provided
/// path a Python executable, and raises an error if the version doesn't match.
/// Else tries to execute the interpreter as "python", "python{major version}",
/// "python{major version}.{minor version}" in order until one
/// is of the version we are expecting.
fn find_interpreter_and_get_config(
    expected_version: &PythonVersion,
) -> Result<(PythonVersion, String, Vec<String>), String> {
    if let Some(sys_executable) = env::var_os("PYTHON_SYS_EXECUTABLE") {
        let interpreter_path = sys_executable
            .to_str()
            .expect("Unable to get PYTHON_SYS_EXECUTABLE value");
        let (interpreter_version, lines) = get_config_from_interpreter(interpreter_path)?;

        if expected_version == &interpreter_version {
            return Ok((interpreter_version, interpreter_path.to_owned(), lines));
        } else {
            return Err(format!(
                "Unsupported python version in PYTHON_SYS_EXECUTABLE={}\n\
                 \tmin version {} != found {}",
                interpreter_path, expected_version, interpreter_version
            ));
        }
    }
    // check default python
    let interpreter_path = "python";
    let (interpreter_version, lines) = get_config_from_interpreter(interpreter_path)?;
    if expected_version == &interpreter_version {
        return Ok((interpreter_version, interpreter_path.to_owned(), lines));
    }

    let major_interpreter_path = &format!("python{}", expected_version.major);
    let (interpreter_version, lines) = get_config_from_interpreter(major_interpreter_path)?;
    if expected_version == &interpreter_version {
        return Ok((
            interpreter_version,
            major_interpreter_path.to_owned(),
            lines,
        ));
    }

    if let Some(minor) = expected_version.minor {
        let minor_interpreter_path = &format!("python{}.{}", expected_version.major, minor);
        let (interpreter_version, lines) = get_config_from_interpreter(minor_interpreter_path)?;
        if expected_version == &interpreter_version {
            return Ok((
                interpreter_version,
                minor_interpreter_path.to_owned(),
                lines,
            ));
        }
    }

    Err(format!("No python interpreter found"))
}

/// Extract compilation vars from the specified interpreter.
fn get_config_from_interpreter(interpreter: &str) -> Result<(PythonVersion, Vec<String>), String> {
    let script = "import sys; import sysconfig; print(sys.version_info[0:2]); \
print(sysconfig.get_config_var('LIBDIR')); \
print(sysconfig.get_config_var('Py_ENABLE_SHARED')); \
print(sysconfig.get_config_var('LDVERSION') or sysconfig.get_config_var('py_version_short')); \
print(sys.exec_prefix);";
    let out = run_python_script(interpreter, script)?;
    let lines: Vec<String> = out.lines().map(|line| line.to_owned()).collect();
    let interpreter_version = get_interpreter_version(&lines[0])?;
    Ok((interpreter_version, lines))
}

/// Deduce configuration from the 'python' in the current PATH and print
/// cargo vars to stdout.
///
/// Note that if the python doesn't satisfy expected_version, this will error.
fn configure_from_path(expected_version: &PythonVersion) -> Result<(String, String), String> {
    let (interpreter_version, interpreter_path, lines) =
        find_interpreter_and_get_config(expected_version)?;

    let libpath: &str = &lines[1];
    let enable_shared: &str = &lines[2];
    let ld_version: &str = &lines[3];
    let exec_prefix: &str = &lines[4];

    let is_extension_module = env::var_os("CARGO_FEATURE_EXTENSION_MODULE").is_some();
    if !is_extension_module || cfg!(target_os = "windows") {
        println!(
            "{}",
            get_rustc_link_lib(&interpreter_version, ld_version, enable_shared == "1").unwrap()
        );
        if libpath != "None" {
            println!("cargo:rustc-link-search=native={}", libpath);
        } else if cfg!(target_os = "windows") {
            println!("cargo:rustc-link-search=native={}\\libs", exec_prefix);
        }
    }

    let mut flags = String::new();

    if let PythonVersion {
        major: 3,
        minor: some_minor,
    } = interpreter_version
    {
        if env::var_os("CARGO_FEATURE_PEP_384").is_some() {
            println!("cargo:rustc-cfg=Py_LIMITED_API");
        }
        if let Some(minor) = some_minor {
            if minor < PY3_MIN_MINOR {
                return Err(format!(
                    "Python 3 required version is 3.{}, current version is 3.{}",
                    PY3_MIN_MINOR, minor
                ));
            }
            for i in 5..(minor + 1) {
                println!("cargo:rustc-cfg=Py_3_{}", i);
                flags += format!("CFG_Py_3_{},", i).as_ref();
            }
            println!("cargo:rustc-cfg=Py_3");
        }
    } else {
        println!("cargo:rustc-cfg=Py_2");
        flags += format!("CFG_Py_2,").as_ref();
    }
    return Ok((interpreter_path, flags));
}

/// Determine the python version we're supposed to be building
/// from the features passed via the environment.
///
/// The environment variable can choose to omit a minor
/// version if the user doesn't care.
fn version_from_env() -> Result<PythonVersion, String> {
    let re = Regex::new(r"CARGO_FEATURE_PYTHON(\d+)(_(\d+))?").unwrap();
    // sort env::vars so we get more explicit version specifiers first
    // so if the user passes e.g. the python-3 feature and the python-3-5
    // feature, python-3-5 takes priority.
    let mut vars = env::vars().collect::<Vec<_>>();
    vars.sort_by(|a, b| b.cmp(a));
    for (key, _) in vars {
        match re.captures(&key) {
            Some(cap) => {
                return Ok(PythonVersion {
                    major: cap.get(1).unwrap().as_str().parse().unwrap(),
                    minor: match cap.get(3) {
                        Some(s) => Some(s.as_str().parse().unwrap()),
                        None => None,
                    },
                });
            }
            None => (),
        }
    }

    Err(
        "Python version feature was not found. At least one python version \
         feature must be enabled."
            .to_owned(),
    )
}

fn check_rustc_version() {
    let ok_channel = supports_features();
    let ok_version = is_min_version(MIN_VERSION);
    let ok_date = is_min_date(MIN_DATE);

    let print_version_err = |version: &str, date: &str| {
        eprintln!(
            "Installed version is: {} ({}). Minimum required: {} ({}).",
            version, date, MIN_VERSION, MIN_DATE
        );
    };

    match (ok_channel, ok_version, ok_date) {
        (Some(ok_channel), Some((ok_version, version)), Some((ok_date, date))) => {
            if !ok_channel {
                eprintln!("Error: pyo3 requires a nightly or dev version of Rust.");
                print_version_err(&*version, &*date);
                panic!("Aborting compilation due to incompatible compiler.")
            }

            if !ok_version || !ok_date {
                eprintln!("Error: pyo3 requires a more recent version of rustc.");
                eprintln!("Use `rustup update` or your preferred method to update Rust");
                print_version_err(&*version, &*date);
                panic!("Aborting compilation due to incompatible compiler.")
            }
        }
        _ => {
            println!(
                "cargo:warning={}",
                "pyo3 was unable to check rustc compatibility."
            );
            println!(
                "cargo:warning={}",
                "Build may fail due to incompatible rustc version."
            );
        }
    }
}

fn main() {
    check_rustc_version();
    // 1. Setup cfg variables so we can do conditional compilation in this
    // library based on the python interpeter's compilation flags. This is
    // necessary for e.g. matching the right unicode and threading interfaces.
    //
    // This locates the python interpreter based on the PATH, which should
    // work smoothly with an activated virtualenv.
    //
    // If you have troubles with your shell accepting '.' in a var name,
    // try using 'env' (sorry but this isn't our fault - it just has to
    // match the pkg-config package name, which is going to have a . in it).
    let version = match version_from_env() {
        Ok(v) => v,
        Err(_) => PythonVersion {
            major: 3,
            minor: None,
        },
    };
    let (python_interpreter_path, flags) = configure_from_path(&version).unwrap();
    let mut config_map = get_config_vars(&python_interpreter_path).unwrap();

    // WITH_THREAD is always on for 3.7
    let (interpreter_version, _, _) = find_interpreter_and_get_config(&version).unwrap();
    if interpreter_version.major == 3 && interpreter_version.minor.unwrap_or(0) >= 7 {
        config_map.insert("WITH_THREAD".to_owned(), "1".to_owned());
    }

    for (key, val) in &config_map {
        match cfg_line_for_var(key, val) {
            Some(line) => println!("{}", line),
            None => (),
        }
    }

    // 2. Export python interpreter compilation flags as cargo variables that
    // will be visible to dependents. All flags will be available to dependent
    // build scripts in the environment variable DEP_PYTHON27_PYTHON_FLAGS as
    // comma separated list; each item in the list looks like
    //
    // {VAL,FLAG}_{flag_name}=val;
    //
    // FLAG indicates the variable is always 0 or 1
    // VAL indicates it can take on any value
    //
    // rust-cypthon/build.rs contains an example of how to unpack this data
    // into cfg flags that replicate the ones present in this library, so
    // you can use the same cfg syntax.
    //let mut flags = flags;
    let flags: String = config_map.iter().fold("".to_owned(), |memo, (key, val)| {
        if is_value(key) {
            memo + format!("VAL_{}={},", key, val).as_ref()
        } else if val != "0" {
            memo + format!("FLAG_{}={},", key, val).as_ref()
        } else {
            memo
        }
    }) + flags.as_str();

    println!(
        "cargo:python_flags={}",
        if flags.len() > 0 {
            &flags[..flags.len() - 1]
        } else {
            ""
        }
    );
}