use semver_parser::range::parse as parse_request;
use semver_parser::version::parse as parse_version;
use semver_parser::version::Version;
use syn::spanned::Spanned;
use url::Url;

use crate::helpers::{indent, read_file, version_matches_request, Result};

fn url_matches(value: &str, pkg_name: &str, version: &Version) -> Result<()> {
    let url = Url::parse(value).map_err(|err| format!("parse error: {}", err))?;

    // We can only reason about docs.rs.
    if url.domain().is_some() && url.domain() != Some("docs.rs") {
        return Ok(());
    }

    // Since docs.rs redirects HTTP traffic to HTTPS, we will ensure
    // that the scheme is "https" here.
    if url.scheme() != "https" {
        return Err(format!("expected \"https\", found {:?}", url.scheme()));
    }

    let mut path_segments = url
        .path_segments()
        .ok_or_else(|| String::from("no path in URL"))?;

    // The package name should not be empty.
    let name = path_segments
        .next()
        .and_then(|path| if path.is_empty() { None } else { Some(path) })
        .ok_or_else(|| String::from("missing package name"))?;

    // The version number should not be empty.
    let request = path_segments
        .next()
        .and_then(|path| if path.is_empty() { None } else { Some(path) })
        .ok_or_else(|| String::from("missing version number"))?;

    // Finally, we check that the package name and version matches.
    if name != pkg_name {
        Err(format!(
            "expected package \"{}\", found \"{}\"",
            pkg_name, name
        ))
    } else {
        // The Rust API Guidelines[1] suggest using an exact version
        // number, but we have relaxed this a little and allow the
        // user to specify the version as just "1" or "1.2". We might
        // make this more strict in the future.
        //
        // [1]: https://rust-lang-nursery.github.io/api-guidelines/documentation.html
        // #crate-sets-html_root_url-attribute-c-html-root
        parse_request(request)
            .map_err(|err| format!("could not parse version in URL: {}", err))
            .and_then(|request| version_matches_request(version, &request))
    }
}

/// Check version numbers in `html_root_url` attributes.
///
/// This function parses the Rust source file in `path` and looks for
/// `html_root_url` attributes. Such an attribute must specify a valid
/// URL and if the URL points to docs.rs, it must be point to the
/// documentation for `pkg_name` and `pkg_version`.
///
/// # Errors
///
/// If any attribute fails the check, an `Err` is returned with a
/// succinct error message. Status information has then already been
/// printed on `stdout`.
pub fn check_html_root_url(path: &str, pkg_name: &str, pkg_version: &str) -> Result<()> {
    let code = read_file(path).map_err(|err| format!("could not read {}: {}", path, err))?;
    let version = parse_version(pkg_version)
        .map_err(|err| format!("bad package version {:?}: {}", pkg_version, err))?;
    let krate: syn::File = syn::parse_file(&code)
        .map_err(|_| format!("could not parse {}: please run \"cargo build\"", path))?;

    println!("Checking doc attributes in {}...", path);
    for attr in krate.attrs {
        if let syn::AttrStyle::Outer = attr.style {
            continue;
        }
        let (ident, nested_meta_items) = match attr.parse_meta() {
            Ok(syn::Meta::List(syn::MetaList { ident, nested, .. })) => (ident, nested),
            _ => continue,
        };

        if ident != "doc" {
            continue;
        }

        for nested_meta_item in nested_meta_items {
            let meta_item = match nested_meta_item {
                syn::NestedMeta::Meta(ref meta_item) => meta_item,
                _ => continue,
            };

            let check_result = match *meta_item {
                syn::Meta::NameValue(syn::MetaNameValue {
                    ref ident, ref lit, ..
                }) if ident == "html_root_url" => {
                    match *lit {
                        // Accept both cooked and raw strings here.
                        syn::Lit::Str(ref s) => url_matches(&s.value(), pkg_name, &version),
                        // A non-string html_root_url is probably an
                        // error, but we leave this check to the
                        // compiler.
                        _ => continue,
                    }
                }
                syn::Meta::Word(ref name) if name == "html_root_url" => {
                    Err(String::from("html_root_url attribute without URL"))
                }
                _ => continue,
            };

            // FIXME: the proc-macro2-0.4.27 crate hides accurate span
            // information behind a procmacro2_semver_exempt flag: the
            // start line is correct, but the end line is always equal
            // to the start. Luckily, most html_root_url attributes
            // are on a single line, so the code below works okay.
            let first_line = attr.span().start().line;
            let last_line = attr.span().end().line;
            // Getting the source code for a span is tracked upstream:
            // https://github.com/alexcrichton/proc-macro2/issues/110.
            let source_lines = code.lines().take(last_line).skip(first_line - 1);
            match check_result {
                Ok(()) => {
                    println!("{} (line {}) ... ok", path, first_line);
                    return Ok(());
                }
                Err(err) => {
                    println!("{} (line {}) ... {} in", path, first_line, err);
                    for line in source_lines {
                        println!("{}", indent(line));
                    }
                    return Err(format!("html_root_url errors in {}", path));
                }
            }
        }
    }

    Ok(())
}

#[cfg(test)]
mod test_url_matches {
    use super::*;

    #[test]
    fn good_url() {
        let ver = parse_version("1.2.3").unwrap();
        assert_eq!(
            url_matches("https://docs.rs/foo/1.2.3", "foo", &ver),
            Ok(())
        );
    }

    #[test]
    fn trailing_slash() {
        let ver = parse_version("1.2.3").unwrap();
        assert_eq!(
            url_matches("https://docs.rs/foo/1.2.3/", "foo", &ver),
            Ok(())
        );
    }

    #[test]
    fn without_patch() {
        let ver = parse_version("1.2.3").unwrap();
        assert_eq!(url_matches("https://docs.rs/foo/1.2", "foo", &ver), Ok(()));
    }

    #[test]
    fn without_minor() {
        let ver = parse_version("1.2.3").unwrap();
        assert_eq!(url_matches("https://docs.rs/foo/1", "foo", &ver), Ok(()));
    }

    #[test]
    fn different_domain() {
        let ver = parse_version("1.2.3").unwrap();
        assert_eq!(url_matches("https://example.net/foo/", "bar", &ver), Ok(()));
    }

    #[test]
    fn different_domain_http() {
        let ver = parse_version("1.2.3").unwrap();
        assert_eq!(
            url_matches("http://example.net/foo/1.2.3", "foo", &ver),
            Ok(())
        );
    }

    #[test]
    fn http_url() {
        let ver = parse_version("1.2.3").unwrap();
        assert_eq!(
            url_matches("http://docs.rs/foo/1.2.3", "foo", &ver),
            Err(String::from("expected \"https\", found \"http\""))
        );
    }

    #[test]
    fn bad_scheme() {
        let ver = parse_version("1.2.3").unwrap();
        assert_eq!(
            url_matches("mailto:foo@example.net", "foo", &ver),
            Err(String::from("expected \"https\", found \"mailto\""))
        );
    }

    #[test]
    fn no_package() {
        let ver = parse_version("1.2.3").unwrap();
        assert_eq!(
            url_matches("https://docs.rs", "foo", &ver),
            Err(String::from("missing package name"))
        );
    }

    #[test]
    fn no_package_trailing_slash() {
        let ver = parse_version("1.2.3").unwrap();
        assert_eq!(
            url_matches("https://docs.rs/", "foo", &ver),
            Err(String::from("missing package name"))
        );
    }

    #[test]
    fn no_version() {
        let ver = parse_version("1.2.3").unwrap();
        assert_eq!(
            url_matches("https://docs.rs/foo", "foo", &ver),
            Err(String::from("missing version number"))
        );
    }

    #[test]
    fn no_version_trailing_slash() {
        let ver = parse_version("1.2.3").unwrap();
        assert_eq!(
            url_matches("https://docs.rs/foo/", "foo", &ver),
            Err(String::from("missing version number"))
        );
    }

    #[test]
    fn bad_url() {
        let ver = parse_version("1.2.3").unwrap();
        assert_eq!(
            url_matches("docs.rs/foo/bar", "foo", &ver),
            Err(String::from("parse error: relative URL without a base"))
        );
    }

    #[test]
    fn bad_pkg_version() {
        let ver = parse_version("1.2.3").unwrap();
        assert_eq!(
            url_matches("https://docs.rs/foo/1.2.bad/", "foo", &ver),
            Err(String::from(
                "could not parse version in URL: \
                 encountered unexpected token: AlphaNumeric(\"bad\")"
            ))
        );
    }

    #[test]
    fn wrong_pkg_name() {
        let ver = parse_version("1.2.3").unwrap();
        assert_eq!(
            url_matches("https://docs.rs/foo/1.2.3/", "bar", &ver),
            Err(String::from("expected package \"bar\", found \"foo\""))
        );
    }
}

#[cfg(test)]
mod test_check_html_root_url {
    use super::*;

    #[test]
    fn bad_path() {
        let no_such_file = if cfg!(unix) {
            "No such file or directory (os error 2)"
        } else {
            "The system cannot find the file specified. (os error 2)"
        };
        let errmsg = format!("could not read no-such-file.md: {}", no_such_file);
        assert_eq!(
            check_html_root_url("no-such-file.md", "foobar", "1.2.3"),
            Err(errmsg)
        );
    }

    #[test]
    fn bad_pkg_version() {
        // This uses the src/lib.rs file from this crate.
        assert_eq!(
            check_html_root_url("src/lib.rs", "foobar", "1.2"),
            Err(String::from(
                "bad package version \"1.2\": expected more input"
            ))
        );
    }
}