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//! The type that stores testing configuration.

use std::path::PathBuf;
use std::collections::HashMap;
use std::fmt;
use tempfile::NamedTempFile;

/// The configuration of the test runner.
#[derive(Clone, Debug)]
pub struct Config
{
    /// A list of file extensions which contain tests.
    pub supported_file_extensions: Vec<String>,
    /// Paths to tests or folders containing tests.
    pub test_paths: Vec<PathBuf>,
    /// Constants that tests can refer to via `@<name>` syntax.
    pub constants: HashMap<String, String>,
    /// A function which used to dynamically lookup variables.
    ///
    /// The default variable lookup can be found at `Config::DEFAULT_VARIABLE_LOOKUP`.
    ///
    /// In your own custom variable lookups, most of the time you will want to
    /// include a fallback call to `Config::DEFAULT_VARIABLE_LOOKUP`.
    pub variable_lookup: VariableLookup,
    /// Whether temporary files generated by the tests should be
    /// cleaned up, where possible.
    ///
    /// This includes temporary files created by using `@tempfile`
    /// variables.
    pub cleanup_temporary_files: bool,
    /// Whether verbose information about resolved variables should be printed to stderr.
    pub dump_variable_resolution: bool,
}

/// A function which can dynamically define newly used variables in a test.
#[derive(Clone)]
pub struct VariableLookup(fn(&str) -> Option<String>);

impl Config
{
    /// The default variable lookup function.
    ///
    /// The supported variables are:
    ///
    /// * Any variable containing the string `"tempfile"`
    ///   * Each distinct variable will be resolved to a distinct temporary file path.
    pub const DEFAULT_VARIABLE_LOOKUP: VariableLookup = VariableLookup(|v| {
        if v.contains("tempfile") {
            let temp_file = NamedTempFile::new().expect("failed to create a temporary file");
            Some(temp_file.into_temp_path().to_str().expect("temp file path is not utf-8").to_owned())
        } else {
            None
        }
    });

    /// Marks a file extension as supported by the runner.
    ///
    /// We only attempt to run tests for files within the extension
    /// whitelist.
    pub fn add_extension<S>(&mut self, ext: S) where S: Into<String> {
        self.supported_file_extensions.push(ext.into())
    }

    /// Adds a search path to the test runner.
    ///
    /// We will recurse through the path to find tests.
    pub fn add_search_path<P>(&mut self, path: P) where P: Into<String> {
        self.test_paths.push(PathBuf::from(path.into()));
    }

    /// Checks if a given extension will have tests run on it
    pub fn is_extension_supported(&self, extension: &str) -> bool {
        self.supported_file_extensions.iter().
            find(|ext| &ext[..] == extension).is_some()
    }

    /// Looks up a variable.
    pub fn lookup_variable<'a>(&self,
                           name: &str,
                           variables: &'a mut HashMap<String, String>)
        -> &'a str {
        if !variables.contains_key(name) {
            match self.variable_lookup.0(name) {
                Some(initial_value) => {
                    variables.insert(name.to_owned(), initial_value.clone());
                },
                None => (),
            }
        }

        variables.get(name).expect("no constant with that name exists")
    }
}

impl Default for Config
{
    fn default() -> Self {
        Config {
            supported_file_extensions: Vec::new(),
            test_paths: Vec::new(),
            constants: HashMap::new(),
            variable_lookup: Config::DEFAULT_VARIABLE_LOOKUP,
            cleanup_temporary_files: true,
            dump_variable_resolution: false,
        }
    }
}

impl fmt::Debug for VariableLookup {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        "<function>".fmt(fmt)
    }
}

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

    #[test]
    fn lookup_variable_works_correctly() {
        let config = Config {
            variable_lookup: VariableLookup(|v| {
                if v.contains("tempfile") { Some(format!("/tmp/temp-{}", v.as_bytes().as_ptr() as usize)) } else { None }
            }),
            constants: vec![("name".to_owned(), "bob".to_owned())].into_iter().collect(),
            ..Config::default()
        };
        let mut variables = config.constants.clone();

        // Can lookup constants
        assert_eq!("bob", config.lookup_variable("name", &mut variables),
                   "cannot lookup constants by name");
        let first_temp = config.lookup_variable("first_tempfile", &mut variables).to_owned();
        let second_temp = config.lookup_variable("second_tempfile", &mut variables).to_owned();

        assert!(first_temp != second_temp,
                "different temporary paths should be different");

        assert_eq!(first_temp,
                   config.lookup_variable("first_tempfile", &mut variables),
                   "first temp has changed its value");

        assert_eq!(second_temp,
                   config.lookup_variable("second_tempfile", &mut variables),
                   "second temp has changed its value");
    }
}