// Copyright 2022 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

use {
    crate::controller::FakeController,
    crate::writer::BufferSink,
    anyhow::{anyhow, bail, Context as _, Result},
    fidl_fuchsia_fuzzer as fuzz,
    fuchsia_fuzzctl::{create_artifact_dir, create_corpus_dir, Writer},
    serde_json::json,
    std::cell::RefCell,
    std::env,
    std::fmt::Debug,
    std::fmt::Display,
    std::fs,
    std::path::{Path, PathBuf},
    std::rc::Rc,
    tempfile::{tempdir, TempDir},
};

pub const TEST_URL: &str = "fuchsia-pkg://fuchsia.com/fake#meta/foo-fuzzer.cm";

/// General purpose test context for the `ffx fuzz` plugin unit tests.
///
/// This object groups several commonly used routines used to capture data produced as a part of
/// unit tests, such as:
///
///   * It can create temporary files and directories, and ensure they persist for duration of
///     the test.
///   * It maintains a list of expected outputs.
///   * It shares a list of actual outputs with a `BufferSink` and can verify that they match
///     its expectations.
///   * It can produce `Writer`s backed by its associated `BufferSink`.
///
#[derive(Clone, Debug)]
pub struct Test {
    // This temporary directory is used indirectly via `root_dir`, but must be kept in scope for
    // the duration of the test to avoid it being deleted prematurely.
    _tmp_dir: Rc<Option<TempDir>>,
    root_dir: PathBuf,
    url: Rc<RefCell<Option<String>>>,
    controller: FakeController,
    requests: Rc<RefCell<Vec<String>>>,
    expected: Vec<Expectation>,
    actual: Rc<RefCell<Vec<u8>>>,
    writer: Writer<BufferSink>,
}

// Output can be tested for exact matches or substring matches.
#[derive(Clone, Debug)]
pub enum Expectation {
    Equals(String),
    Contains(String),
}

impl Test {
    /// Creates a new `Test`.
    ///
    /// When running tests, users may optionally set the FFX_FUZZ_ECHO_TEST_OUTPUT environment
    /// variable, which will cause this object to use an existing directory rather than create a
    /// temporary one.
    pub fn try_new() -> Result<Self> {
        let (tmp_dir, root_dir) = match env::var("FFX_FUZZ_TEST_ROOT_DIR") {
            Ok(root_dir) => (None, PathBuf::from(root_dir)),
            Err(_) => {
                let tmp_dir = tempdir().context("failed to create test directory")?;
                let root_dir = PathBuf::from(tmp_dir.path());
                (Some(tmp_dir), root_dir)
            }
        };
        let actual = Rc::new(RefCell::new(Vec::new()));
        let mut writer = Writer::new(BufferSink::new(Rc::clone(&actual)));
        writer.use_colors(false);
        Ok(Self {
            _tmp_dir: Rc::new(tmp_dir),
            root_dir,
            url: Rc::new(RefCell::new(None)),
            controller: FakeController::new(),
            requests: Rc::new(RefCell::new(Vec::new())),
            expected: Vec::new(),
            actual,
            writer,
        })
    }

    /// Returns the writable temporary directory for this test.
    pub fn root_dir(&self) -> &Path {
        self.root_dir.as_path()
    }

    /// Creates a directory under this object's `root_dir`.
    ///
    /// The given `path` may be relative or absolute, but if it is the latter it must be
    /// prefixed with this object's `root_dir`.
    ///
    /// Returns a `PathBuf` on success and an error if the `path` is outside the `root_dir` or
    /// the filesystem returns an error.
    ///
    pub fn create_dir<P: AsRef<Path>>(&self, path: P) -> Result<PathBuf> {
        let path = path.as_ref();
        let mut abspath = PathBuf::from(self.root_dir());
        if path.is_relative() {
            abspath.push(path);
        } else if path.starts_with(self.root_dir()) {
            abspath = PathBuf::from(path);
        } else {
            bail!(
                "cannot create test directories outside the test root: {}",
                path.to_string_lossy()
            );
        }
        fs::create_dir_all(&abspath).with_context(|| {
            format!("failed to create '{}' directory", abspath.to_string_lossy())
        })?;
        Ok(abspath)
    }

    /// Returns the path where the fuzzer will store artifacts.
    pub fn artifact_dir(&self) -> PathBuf {
        create_artifact_dir(&self.root_dir).unwrap()
    }

    /// Returns the path where the fuzzer will store its corpus of the given type.
    pub fn corpus_dir(&self, corpus_type: fuzz::Corpus) -> PathBuf {
        create_corpus_dir(&self.root_dir, corpus_type).unwrap()
    }

    /// Creates a fake ".fx-build-dir" file for testing.
    ///
    /// The ".fx-build-dir" file will be created under this object's `root_dir`, and will
    /// contain the `relative_path` to the build directory. Except for some `util::tests`, unit
    /// tests should prefer `create_tests_json`.
    ///
    /// Returns an error if any filesystem operations fail.
    ///
    pub fn write_fx_build_dir<P: AsRef<Path>>(&self, build_dir: P) -> Result<()> {
        let build_dir = build_dir.as_ref();
        let mut fx_build_dir = PathBuf::from(self.root_dir());
        fx_build_dir.push(".fx-build-dir");
        let build_dir = build_dir.to_string_lossy().to_string();
        fs::write(&fx_build_dir, &build_dir)
            .with_context(|| format!("failed to write to '{}'", fx_build_dir.to_string_lossy()))?;
        Ok(())
    }

    /// Creates a fake "tests.json" file for testing.
    ///
    /// The "tests.json" will be created under the `relative_path` from this object's `root_dir`
    /// and will contain the given `contents`. Except for some `util::tests`, unit tests should
    /// prefer `create_tests_json`.
    ///
    /// Returns an error if any filesystem operations fail.
    ///
    pub fn write_tests_json<P: AsRef<Path>, S: AsRef<str>>(
        &self,
        build_dir: P,
        contents: S,
    ) -> Result<PathBuf> {
        let build_dir = build_dir.as_ref();
        let mut tests_json = PathBuf::from(build_dir);
        tests_json.push("tests.json");
        fs::write(&tests_json, contents.as_ref())
            .with_context(|| format!("failed to write to '{}'", tests_json.to_string_lossy()))?;
        Ok(tests_json)
    }

    /// Creates a fake "tests.json" file for testing.
    ///
    /// The "tests.json" will include an array of valid JSON objects for the given `urls`.
    ///
    /// Returns an error if any filesystem operations fail.
    ///
    pub fn create_tests_json<D: Display>(&self, urls: impl Iterator<Item = D>) -> Result<PathBuf> {
        let build_dir = self
            .create_dir("out/default")
            .context("failed to create build directory for 'tests.json'")?;
        self.write_fx_build_dir(&build_dir).with_context(|| {
            format!("failed to set build directory to '{}'", build_dir.to_string_lossy())
        })?;

        let json_data: Vec<_> = urls
            .map(|url| {
                json!({
                    "test": {
                        "build_rule": "fuchsia_fuzzer_package",
                        "package_url": url.to_string()
                    }
                })
            })
            .collect();
        let json_data = json!(json_data);
        self.write_tests_json(&build_dir, json_data.to_string()).with_context(|| {
            format!("failed to create '{}/tests.json'", build_dir.to_string_lossy())
        })
    }

    /// Creates several temporary `files` from the given iterator for testing.
    ///
    /// Each file's contents will simpl be its name, which is taken from the given `files`.
    ///
    /// Returns an error if writing to the filesystem fails.
    ///
    pub fn create_test_files<P: AsRef<Path>, D: Display>(
        &self,
        test_dir: P,
        files: impl Iterator<Item = D>,
    ) -> Result<()> {
        let test_dir = self.create_dir(test_dir)?;
        for filename in files {
            let filename = filename.to_string();
            fs::write(test_dir.join(&filename), filename.as_bytes())
                .with_context(|| format!("failed to write to '{}'", filename))?;
        }
        Ok(())
    }

    /// Clones the `RefCell` holding the URL provided to the fake manager.
    pub fn url(&self) -> Rc<RefCell<Option<String>>> {
        self.url.clone()
    }

    /// Clones the fake fuzzer controller "connected" by the fake manager.
    pub fn controller(&self) -> FakeController {
        self.controller.clone()
    }

    /// Records a FIDL request made to a test fake.
    pub fn record<S: AsRef<str>>(&mut self, request: S) {
        let mut requests_mut = self.requests.borrow_mut();
        requests_mut.push(request.as_ref().to_string());
    }

    /// Returns the recorded FIDL requests.
    ///
    /// As a side-effect, this resets the recorded requests.
    ///
    pub fn requests(&mut self) -> Vec<String> {
        let mut requests_mut = self.requests.borrow_mut();
        let requests = requests_mut.clone();
        *requests_mut = Vec::new();
        requests
    }

    /// Adds an expectation that an output written to the `BufferSink` will exactly match `msg`.
    pub fn output_matches<T: AsRef<str> + Display>(&mut self, msg: T) {
        let msg = msg.as_ref().trim().to_string();
        if !msg.is_empty() {
            self.expected.push(Expectation::Equals(msg));
        }
    }

    /// Adds an expectation that an output written to the `BufferSink` will contain `msg`.
    pub fn output_includes<T: AsRef<str> + Display>(&mut self, msg: T) {
        let msg = msg.as_ref().trim().to_string();
        if !msg.is_empty() {
            self.expected.push(Expectation::Contains(msg));
        }
    }

    /// Iterates over the expected and actual output and verifies expectations are met.
    pub fn verify_output(&mut self) -> Result<()> {
        let actual: Vec<u8> = {
            let mut actual = self.actual.borrow_mut();
            actual.drain(..).collect()
        };
        let actual = String::from_utf8_lossy(&actual);
        let mut actual: Vec<String> = actual.split("\n").map(|s| s.trim().to_string()).collect();
        actual.retain(|s| !s.is_empty());
        let mut actual = actual.into_iter();

        // `Contains` expectations may be surrounded by extra lines.
        let mut extra = false;
        for expectation in self.expected.drain(..) {
            loop {
                let line = actual.next().ok_or(anyhow!("unmet expectation: {:?}", expectation))?;
                match &expectation {
                    Expectation::Equals(msg) if line == *msg => {
                        extra = false;
                        break;
                    }
                    Expectation::Equals(_msg) if extra => continue,
                    Expectation::Equals(msg) => {
                        bail!("mismatch:\n  actual=`{}`\nexpected=`{}`", line, msg)
                    }
                    Expectation::Contains(msg) => {
                        extra = true;
                        if line.contains(msg) {
                            break;
                        }
                    }
                }
            }
        }
        if !extra {
            if let Some(line) = actual.next() {
                bail!("unexpected line: {}", line);
            }
        }
        Ok(())
    }

    /// Returns a `Writer` using the `BufferSink` associated with this object.
    pub fn writer(&self) -> &Writer<BufferSink> {
        &self.writer
    }
}