//! Read configurations files.

#![deny(missing_docs_in_private_items)]

use std::{env, fmt, fs, io, path};
use std::io::Read;
use syntax::{ast, codemap};
use toml;

/// Get the configuration file from arguments.
pub fn file_from_args(args: &[codemap::Spanned<ast::NestedMetaItemKind>]) -> Result<Option<path::PathBuf>, (&'static str, codemap::Span)> {
    for arg in args.iter().filter_map(|a| a.meta_item()) {
        if arg.name() == "conf_file" {
            return match arg.node {
                ast::MetaItemKind::Word |
                ast::MetaItemKind::List(_) => {
                    Err(("`conf_file` must be a named value", arg.span))
                }
                ast::MetaItemKind::NameValue(ref value) => {
                    if let ast::LitKind::Str(ref file, _) = value.node {
                        Ok(Some(file.to_string().into()))
                    } else {
                        Err(("`conf_file` value must be a string", value.span))
                    }
                }
            };
        }
    }

    Ok(None)
}

/// Error from reading a configuration file.
#[derive(Debug)]
pub enum Error {
    /// An I/O error.
    Io(io::Error),
    /// The file is not valid TOML.
    Toml(Vec<toml::ParserError>),
    /// Type error.
    Type(
        /// The name of the key.
        &'static str,
        /// The expected type.
        &'static str,
        /// The type we got instead.
        &'static str
    ),
    /// There is an unknown key is the file.
    UnknownKey(String),
}

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
        match *self {
            Error::Io(ref err) => err.fmt(f),
            Error::Toml(ref errs) => {
                let mut first = true;
                for err in errs {
                    if !first {
                        try!(", ".fmt(f));
                        first = false;
                    }

                    try!(err.fmt(f));
                }

                Ok(())
            }
            Error::Type(key, expected, got) => {
                write!(f, "`{}` is expected to be a `{}` but is a `{}`", key, expected, got)
            }
            Error::UnknownKey(ref key) => write!(f, "unknown key `{}`", key),
        }
    }
}

impl From<io::Error> for Error {
    fn from(e: io::Error) -> Self {
        Error::Io(e)
    }
}

macro_rules! define_Conf {
    ($(#[$doc: meta] ($toml_name: tt, $rust_name: ident, $default: expr => $($ty: tt)+),)+) => {
        /// Type used to store lint configuration.
        pub struct Conf {
            $(#[$doc] pub $rust_name: define_Conf!(TY $($ty)+),)+
        }

        impl Default for Conf {
            fn default() -> Conf {
                Conf {
                    $($rust_name: define_Conf!(DEFAULT $($ty)+, $default),)+
                }
            }
        }

        impl Conf {
            /// Set the property `name` (which must be the `toml` name) to the given value
            #[allow(cast_sign_loss)]
            fn set(&mut self, name: String, value: toml::Value) -> Result<(), Error> {
                match name.as_str() {
                    $(
                        define_Conf!(PAT $toml_name) => {
                            if let Some(value) = define_Conf!(CONV $($ty)+, value) {
                                self.$rust_name = value;
                            }
                            else {
                                return Err(Error::Type(define_Conf!(EXPR $toml_name),
                                                       stringify!($($ty)+),
                                                       value.type_str()));
                            }
                        },
                    )+
                    "third-party" => {
                        // for external tools such as clippy-service
                        return Ok(());
                    }
                    _ => {
                        return Err(Error::UnknownKey(name));
                    }
                }

                Ok(())
            }
        }
    };

    // hack to convert tts
    (PAT $pat: pat) => { $pat };
    (EXPR $e: expr) => { $e };
    (TY $ty: ty) => { $ty };

    // how to read the value?
    (CONV i64, $value: expr) => { $value.as_integer() };
    (CONV u64, $value: expr) => { $value.as_integer().iter().filter_map(|&i| if i >= 0 { Some(i as u64) } else { None }).next() };
    (CONV String, $value: expr) => { $value.as_str().map(Into::into) };
    (CONV Vec<String>, $value: expr) => {{
        let slice = $value.as_slice();

        if let Some(slice) = slice {
            if slice.iter().any(|v| v.as_str().is_none()) {
                None
            }
            else {
                Some(slice.iter().map(|v| v.as_str().unwrap_or_else(|| unreachable!()).to_owned()).collect())
            }
        }
        else {
            None
        }
    }};

    // provide a nicer syntax to declare the default value of `Vec<String>` variables
    (DEFAULT Vec<String>, $e: expr) => { $e.iter().map(|&e| e.to_owned()).collect() };
    (DEFAULT $ty: ty, $e: expr) => { $e };
}

define_Conf! {
    /// Lint: BLACKLISTED_NAME. The list of blacklisted names to lint about
    ("blacklisted-names", blacklisted_names, ["foo", "bar", "baz", "quux"] => Vec<String>),
    /// Lint: CYCLOMATIC_COMPLEXITY. The maximum cyclomatic complexity a function can have
    ("cyclomatic-complexity-threshold", cyclomatic_complexity_threshold, 25 => u64),
    /// Lint: DOC_MARKDOWN. The list of words this lint should not consider as identifiers needing ticks
    ("doc-valid-idents", doc_valid_idents, ["MiB", "GiB", "TiB", "PiB", "EiB", "DirectX", "GPLv2", "GPLv3", "GitHub", "IPv4", "IPv6", "JavaScript", "NaN", "OAuth", "OpenGL", "TrueType", "iOS", "macOS"] => Vec<String>),
    /// Lint: TOO_MANY_ARGUMENTS. The maximum number of argument a function or method can have
    ("too-many-arguments-threshold", too_many_arguments_threshold, 7 => u64),
    /// Lint: TYPE_COMPLEXITY. The maximum complexity a type can have
    ("type-complexity-threshold", type_complexity_threshold, 250 => u64),
    /// Lint: MANY_SINGLE_CHAR_NAMES. The maximum number of single char bindings a scope may have
    ("single-char-binding-names-threshold", max_single_char_names, 5 => u64),
    /// Lint: BOXED_LOCAL. The maximum size of objects (in bytes) that will be linted. Larger objects are ok on the heap
    ("too-large-for-stack", too_large_for_stack, 200 => u64),
    /// Lint: ENUM_VARIANT_NAMES. The minimum number of enum variants for the lints about variant names to trigger
    ("enum-variant-name-threshold", enum_variant_name_threshold, 3 => u64),
}

/// Search for the configuration file.
pub fn lookup_conf_file() -> io::Result<Option<path::PathBuf>> {
    /// Possible filename to search for.
    const CONFIG_FILE_NAMES: [&'static str; 2] = [".clippy.toml", "clippy.toml"];

    let mut current = try!(env::current_dir());

    loop {
        for config_file_name in &CONFIG_FILE_NAMES {
            let config_file = current.join(config_file_name);
            match fs::metadata(&config_file) {
                // Only return if it's a file to handle the unlikely situation of a directory named
                // `clippy.toml`.
                Ok(ref md) if md.is_file() => return Ok(Some(config_file)),
                // Return the error if it's something other than `NotFound`; otherwise we didn't
                // find the project file yet, and continue searching.
                Err(e) => {
                    if e.kind() != io::ErrorKind::NotFound {
                        return Err(e);
                    }
                }
                _ => (),
            }
        }

        // If the current directory has no parent, we're done searching.
        if !current.pop() {
            return Ok(None);
        }
    }
}

/// Read the `toml` configuration file.
///
/// In case of error, the function tries to continue as much as possible.
pub fn read(path: Option<&path::Path>) -> (Conf, Vec<Error>) {
    let mut conf = Conf::default();
    let mut errors = Vec::new();

    let path = if let Some(path) = path {
        path
    } else {
        return (conf, errors);
    };

    let file = match fs::File::open(path) {
        Ok(mut file) => {
            let mut buf = String::new();

            if let Err(err) = file.read_to_string(&mut buf) {
                errors.push(err.into());
                return (conf, errors);
            }

            buf
        }
        Err(err) => {
            errors.push(err.into());
            return (conf, errors);
        }
    };

    let mut parser = toml::Parser::new(&file);
    let toml = if let Some(toml) = parser.parse() {
        toml
    } else {
        errors.push(Error::Toml(parser.errors));
        return (conf, errors);
    };

    for (key, value) in toml {
        if let Err(err) = conf.set(key, value) {
            errors.push(err);
        }
    }

    (conf, errors)
}