// Copyright 2020 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::{
        descriptor::EventDescriptor,
        events::{Event, EventStream, ExitStatus},
    },
    anyhow::{format_err, Error},
    fidl_fuchsia_sys2 as fsys,
    regex::RegexSet,
    std::convert::TryFrom,
};

// A matcher that implements this trait is able to match against values of type `T`.
// A matcher corresponds to a field named `NAME`.
trait RawFieldMatcher<T>: Clone + std::fmt::Debug {
    const NAME: &'static str;
    fn matches(&self, other: &T) -> bool;
}

#[derive(Clone, Debug)]
pub struct EventTypeMatcher {
    event_type: fsys::EventType,
}

impl EventTypeMatcher {
    fn new(event_type: fsys::EventType) -> Self {
        Self { event_type }
    }

    pub fn value(&self) -> &fsys::EventType {
        &self.event_type
    }
}

impl RawFieldMatcher<fsys::EventType> for EventTypeMatcher {
    const NAME: &'static str = "event_type";

    fn matches(&self, other: &fsys::EventType) -> bool {
        self.event_type == *other
    }
}

#[derive(Clone, Debug, PartialEq)]
pub struct CapabilityNameMatcher {
    capability_name: String,
}

impl CapabilityNameMatcher {
    fn new(capability_name: impl Into<String>) -> Self {
        Self { capability_name: capability_name.into() }
    }
}

impl RawFieldMatcher<String> for CapabilityNameMatcher {
    const NAME: &'static str = "name";

    fn matches(&self, other: &String) -> bool {
        self.capability_name == *other
    }
}

#[derive(Clone, Debug)]
pub struct MonikerMatcher {
    monikers: RegexSet,
}

impl MonikerMatcher {
    fn new<I, S>(monikers: I) -> Self
    where
        S: AsRef<str>,
        I: IntoIterator<Item = S>,
    {
        Self { monikers: RegexSet::new(monikers).unwrap() }
    }
}

impl RawFieldMatcher<String> for MonikerMatcher {
    const NAME: &'static str = "target_monikers";

    fn matches(&self, other: &String) -> bool {
        self.monikers.is_match(other)
    }
}

#[derive(Debug, PartialEq, Eq, Clone, Ord, PartialOrd)]
/// Used for matching against events. If the matcher doesn't crash the exit code
/// then `AnyCrash` can be used to match against any Stopped event caused by a crash.
/// that indicate failure are crushed into `Crash`.
pub enum ExitStatusMatcher {
    Clean,
    AnyCrash,
    Crash(i32),
}

impl RawFieldMatcher<ExitStatus> for ExitStatusMatcher {
    const NAME: &'static str = "exit_status";

    fn matches(&self, other: &ExitStatus) -> bool {
        match (self, other) {
            (ExitStatusMatcher::Clean, ExitStatus::Clean) => true,
            (ExitStatusMatcher::AnyCrash, ExitStatus::Crash(_)) => true,
            (ExitStatusMatcher::Crash(exit_code), ExitStatus::Crash(other_exit_code)) => {
                exit_code == other_exit_code
            }
            _ => false,
        }
    }
}

#[derive(Clone, Debug, PartialEq)]
pub struct EventIsOkMatcher {
    event_is_ok: bool,
}

impl EventIsOkMatcher {
    fn new(event_is_ok: bool) -> Self {
        Self { event_is_ok }
    }
}

impl RawFieldMatcher<bool> for EventIsOkMatcher {
    const NAME: &'static str = "event_is_ok";

    fn matches(&self, other: &bool) -> bool {
        self.event_is_ok == *other
    }
}

/// A field matcher is an optional matcher that compares against an optional field.
/// If there is a mismatch, an error string is generated. If there is no matcher specified,
/// then there is no error. If there is matcher without a corresponding field then that's a missing
/// field error. Otherwise, the FieldMatcher delegates to the RawFieldMatcher to determine if the
/// matcher matches against the raw field.
trait FieldMatcher<T> {
    fn matches(&self, other: &Option<T>) -> Result<(), Error>;
}

impl<LeftHandSide, RightHandSide> FieldMatcher<RightHandSide> for Option<LeftHandSide>
where
    LeftHandSide: RawFieldMatcher<RightHandSide>,
    RightHandSide: std::fmt::Debug,
{
    fn matches(&self, other: &Option<RightHandSide>) -> Result<(), Error> {
        match (self, other) {
            (Some(value), Some(other_value)) => match value.matches(other_value) {
                true => Ok(()),
                false => Err(format_err!(
                    "Field `{}` mismatch. Expected: {:?}, Actual: {:?}",
                    LeftHandSide::NAME,
                    value,
                    other_value
                )),
            },
            (Some(_), None) => Err(format_err!("Missing field `{}`.", LeftHandSide::NAME)),
            (None, _) => Ok(()),
        }
    }
}

#[derive(Clone, Debug, Default)]
pub struct EventMatcher {
    pub event_type: Option<EventTypeMatcher>,
    pub target_monikers: Option<MonikerMatcher>,
    pub capability_name: Option<CapabilityNameMatcher>,
    pub exit_status: Option<ExitStatusMatcher>,
    pub event_is_ok: Option<EventIsOkMatcher>,
}

impl EventMatcher {
    pub fn ok() -> Self {
        let mut matcher = EventMatcher::default();
        matcher.event_is_ok = Some(EventIsOkMatcher::new(true));
        matcher
    }

    pub fn err() -> Self {
        let mut matcher = EventMatcher::default();
        matcher.event_is_ok = Some(EventIsOkMatcher::new(false));
        matcher
    }

    pub fn r#type(mut self, event_type: fsys::EventType) -> Self {
        self.event_type = Some(EventTypeMatcher::new(event_type));
        self
    }

    /// The expected target moniker as a regular expression.
    pub fn moniker(self, moniker: impl Into<String>) -> Self {
        self.monikers(&[moniker.into()])
    }

    /// The expected target monikers as regular expressions. This will match against
    /// regular expression in the iterator provided.
    pub fn monikers<I, S>(mut self, monikers: I) -> Self
    where
        S: AsRef<str>,
        I: IntoIterator<Item = S>,
    {
        self.target_monikers = Some(MonikerMatcher::new(monikers));
        self
    }

    /// The expected capability id.
    pub fn capability_id(mut self, capability_id: impl Into<String>) -> Self {
        self.capability_name = Some(CapabilityNameMatcher::new(capability_id));
        self
    }

    /// The expected exit status. Only applies to the Stop event.
    pub fn stop(mut self, exit_status: Option<ExitStatusMatcher>) -> Self {
        self.event_type = Some(EventTypeMatcher::new(fsys::EventType::Stopped));
        self.exit_status = exit_status;
        self
    }

    /// Expects the next event to match the provided EventMatcher.
    /// Returns the casted type if successful and an error otherwise.
    pub async fn expect_match<T: Event>(&mut self, event_stream: &mut EventStream) -> T {
        let event = event_stream.next().await.unwrap();
        let descriptor = EventDescriptor::try_from(&event).unwrap();
        let event = T::try_from(event).unwrap();
        self.matches(&descriptor).unwrap();
        event
    }

    /// Waits for an event matching the matcher.
    /// Implicitly resumes all other events.
    /// Returns the casted type if successful and an error otherwise.
    pub async fn wait<T: Event>(self, event_stream: &mut EventStream) -> Result<T, Error> {
        let expected_event_matcher = self.r#type(T::TYPE);
        loop {
            let event = event_stream.next().await?;
            let descriptor = EventDescriptor::try_from(&event)?;
            if expected_event_matcher.matches(&descriptor).is_ok() {
                return T::try_from(event);
            }
        }
    }

    pub fn matches(&self, other: &EventDescriptor) -> Result<(), Error> {
        self.event_type.matches(&other.event_type)?;
        self.target_monikers.matches(&other.target_moniker)?;
        self.capability_name.matches(&other.capability_name)?;
        self.exit_status.matches(&other.exit_status)?;
        self.event_is_ok.matches(&other.event_is_ok)?;
        Ok(())
    }
}