// Copyright (c) Facebook, Inc. and its affiliates.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use std::collections::{BTreeMap, BTreeSet};
use std::fmt;
use std::str::FromStr;
use std::time::{Duration, Instant, SystemTime};

use anyhow::{anyhow, Context, Result};
use serde::{Deserialize, Serialize};

#[macro_use]
pub mod collector;
pub mod cgroup;
#[cfg(test)]
mod field_ids;
pub mod network;
pub mod process;
pub mod sample;
mod sample_model;
pub mod system;

pub use cgroup::*;
pub use collector::*;
pub use network::*;
pub use process::*;
pub use sample::*;
pub use system::*;

#[cfg(fbcode_build)]
mod facebook;
#[cfg(fbcode_build)]
pub use crate::facebook::*;

/// A wrapper for different field types used in Models. By this way we can query
/// different fields in a single function without using Box.
#[derive(Clone, Debug)]
pub enum Field {
    U32(u32),
    U64(u64),
    I32(i32),
    I64(i64),
    F64(f64),
    Str(String),
    PidState(procfs::PidState),
}

impl From<Field> for i64 {
    fn from(field: Field) -> i64 {
        match field {
            Field::I32(v) => v as i64,
            Field::I64(v) => v as i64,
            _ => panic!("Operation for unsupported types"),
        }
    }
}

impl From<Field> for f64 {
    fn from(field: Field) -> f64 {
        match field {
            Field::U32(v) => v as f64,
            Field::U64(v) => v as f64,
            Field::I32(v) => v as f64,
            Field::I64(v) => v as f64,
            Field::F64(v) => v,
            _ => panic!("Operation for unsupported types"),
        }
    }
}

impl From<Field> for String {
    fn from(field: Field) -> String {
        match field {
            Field::Str(v) => v,
            _ => panic!("Operation for unsupported types"),
        }
    }
}

impl From<u32> for Field {
    fn from(v: u32) -> Self {
        Field::U32(v)
    }
}

impl From<u64> for Field {
    fn from(v: u64) -> Self {
        Field::U64(v)
    }
}

impl From<i32> for Field {
    fn from(v: i32) -> Self {
        Field::I32(v)
    }
}

impl From<i64> for Field {
    fn from(v: i64) -> Self {
        Field::I64(v)
    }
}

impl From<f64> for Field {
    fn from(v: f64) -> Self {
        Field::F64(v)
    }
}

impl From<String> for Field {
    fn from(v: String) -> Self {
        Field::Str(v)
    }
}

impl From<procfs::PidState> for Field {
    fn from(v: procfs::PidState) -> Self {
        Field::PidState(v)
    }
}

impl<T: Into<Field> + Clone> From<&T> for Field {
    fn from(v: &T) -> Self {
        v.clone().into()
    }
}

impl std::ops::Add for Field {
    type Output = Self;

    fn add(self, other: Self) -> Self {
        match (self, other) {
            (Field::U64(s), Field::U64(o)) => (s + o).into(),
            (Field::I32(s), Field::I32(o)) => (s + o).into(),
            (Field::I64(s), Field::I64(o)) => (s + o).into(),
            (Field::F64(s), Field::F64(o)) => (s + o).into(),
            (Field::Str(s), Field::Str(o)) => (s + &o).into(),
            _ => panic!("Operation for unsupported types"),
        }
    }
}

impl PartialEq for Field {
    fn eq(&self, other: &Self) -> bool {
        match (self, other) {
            (Field::U64(s), Field::U64(o)) => s == o,
            (Field::I32(s), Field::I32(o)) => s == o,
            (Field::I64(s), Field::I64(o)) => s == o,
            (Field::F64(s), Field::F64(o)) => s == o,
            (Field::Str(s), Field::Str(o)) => s == o,
            (Field::PidState(s), Field::PidState(o)) => s == o,
            _ => false,
        }
    }
}

impl PartialOrd for Field {
    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
        match (self, other) {
            (Field::U64(s), Field::U64(o)) => s.partial_cmp(o),
            (Field::I32(s), Field::I32(o)) => s.partial_cmp(o),
            (Field::I64(s), Field::I64(o)) => s.partial_cmp(o),
            (Field::F64(s), Field::F64(o)) => s.partial_cmp(o),
            (Field::Str(s), Field::Str(o)) => s.partial_cmp(o),
            (Field::PidState(s), Field::PidState(o)) => s.partial_cmp(o),
            _ => None,
        }
    }
}

impl fmt::Display for Field {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Field::U32(v) => v.fmt(f),
            Field::U64(v) => v.fmt(f),
            Field::I32(v) => v.fmt(f),
            Field::I64(v) => v.fmt(f),
            Field::F64(v) => v.fmt(f),
            Field::Str(v) => v.fmt(f),
            Field::PidState(v) => v.fmt(f),
        }
    }
}

/// Each Model is composed of Fields and optionally sub-Models. The Queriable
/// trait let us query() a Model for a particular Field within the hierarchy
/// with the given FieldId.
pub trait Queriable {
    type FieldId: FieldId<Queriable = Self>;
    fn query(&self, field_id: &Self::FieldId) -> Option<Field>;
}

/// Marker trait to bind FieldId back to Queriable for type inference.
pub trait FieldId: Sized {
    type Queriable: Queriable<FieldId = Self> + ?Sized;
}

pub fn sort_queriables<T: Queriable>(queriables: &mut [&T], field_id: &T::FieldId, reverse: bool) {
    queriables.sort_by(|lhs, rhs| {
        let order = lhs
            .query(field_id)
            .partial_cmp(&rhs.query(field_id))
            .unwrap_or(std::cmp::Ordering::Equal);
        if reverse { order.reverse() } else { order }
    });
}

/// An enum that can iterate its variants. Ones without parameters are unit
/// variants. Ones with exactly one parameter that is also IterEnum are nested
/// variants. Can be auto derived with below_derive::EnumIter.
/// Use this trait to programmatically list available variants in a FieldId.
pub trait EnumIter: Sized + 'static {
    /// Return iterator for unit variants only.
    fn unit_variant_iter() -> Box<dyn Iterator<Item = Self>> {
        Box::new(std::iter::empty())
    }
    /// Return iterator for unit variants as well as nested variants.
    fn all_variant_iter() -> Box<dyn Iterator<Item = Self>> {
        Box::new(std::iter::empty())
    }
}

/// Models containing sub-Models with its own type, similar to a node in a tree.
/// Such Model has a depth value for illustrating the tree hierarchy.
pub trait Recursive {
    fn get_depth(&self) -> usize;
}

/// Type that makes Vec Queriable if Vec's inner type is Queriable. Uses `idx`
/// to query into a Vec. Uses `subquery_id` to query into the selected item.
#[derive(Clone, Debug, PartialEq)]
pub struct VecFieldId<F: FieldId> {
    /// None is only for listing variants and otherwise invalid.
    pub idx: Option<usize>,
    pub subquery_id: F,
}

impl<F: FieldId> FieldId for VecFieldId<F>
where
    <F as FieldId>::Queriable: Sized,
{
    type Queriable = Vec<F::Queriable>;
}

impl<F: FieldId + EnumIter> EnumIter for VecFieldId<F> {
    fn all_variant_iter() -> Box<dyn Iterator<Item = Self>> {
        Box::new(F::all_variant_iter().map(|v| VecFieldId {
            // Dynamic parameter is irrelevant to variant listing
            idx: None,
            subquery_id: v,
        }))
    }
}

impl<F: FieldId + ToString> ToString for VecFieldId<F> {
    fn to_string(&self) -> String {
        match self.idx {
            Some(idx) => format!("{}.{}", idx, self.subquery_id.to_string()),
            None => format!("<idx>.{}", self.subquery_id.to_string()),
        }
    }
}

impl<F: FieldId + FromStr> FromStr for VecFieldId<F>
where
    <F as FromStr>::Err: Into<anyhow::Error>,
{
    type Err = anyhow::Error;
    fn from_str(s: &str) -> std::result::Result<Self, Self::Err> {
        if let Some(dot_idx) = s.find('.') {
            Ok(Self {
                idx: Some(s[..dot_idx].parse()?),
                subquery_id: F::from_str(&s[dot_idx + 1..]).map_err(Into::into)?,
            })
        } else {
            Err(anyhow!(
                "Unable to find a variant of the given enum matching string `{}`.",
                s,
            ))
        }
    }
}

impl<Q: Queriable> Queriable for Vec<Q> {
    type FieldId = VecFieldId<Q::FieldId>;
    fn query(&self, field_id: &Self::FieldId) -> Option<Field> {
        self.get(field_id.idx?)
            .and_then(|f| f.query(&field_id.subquery_id))
    }
}

/// Type that makes BTreeMap Queriable if its value is Queriable. Uses `key`
/// to query into a map. Uses `subquery_id` to query into the selected value.
#[derive(Clone, Debug, PartialEq)]
pub struct BTreeMapFieldId<K, F: FieldId> {
    /// None is only for listing variants and otherwise invalid.
    pub key: Option<K>,
    pub subquery_id: F,
}

impl<K: Ord, F: FieldId> FieldId for BTreeMapFieldId<K, F>
where
    <F as FieldId>::Queriable: Sized,
{
    type Queriable = BTreeMap<K, F::Queriable>;
}

impl<K: Ord + 'static, F: FieldId + EnumIter> EnumIter for BTreeMapFieldId<K, F> {
    fn all_variant_iter() -> Box<dyn Iterator<Item = Self>> {
        Box::new(F::all_variant_iter().map(|v| BTreeMapFieldId {
            // Dynamic parameter is irrelevant to variant listing
            key: None,
            subquery_id: v,
        }))
    }
}

impl<K: ToString, F: FieldId + ToString> ToString for BTreeMapFieldId<K, F> {
    fn to_string(&self) -> String {
        match &self.key {
            Some(key) => format!("{}.{}", key.to_string(), self.subquery_id.to_string()),
            None => format!("<key>.{}", self.subquery_id.to_string()),
        }
    }
}

impl<K: FromStr, F: FieldId + FromStr> FromStr for BTreeMapFieldId<K, F>
where
    <K as FromStr>::Err: Into<anyhow::Error>,
    <F as FromStr>::Err: Into<anyhow::Error>,
{
    type Err = anyhow::Error;
    fn from_str(s: &str) -> std::result::Result<Self, Self::Err> {
        // Only works with keys that don't contain dot
        if let Some(dot_idx) = s.find('.') {
            Ok(Self {
                key: Some(K::from_str(&s[..dot_idx]).map_err(Into::into)?),
                subquery_id: F::from_str(&s[dot_idx + 1..]).map_err(Into::into)?,
            })
        } else {
            Err(anyhow!(
                "Unable to find a variant of the given enum matching string `{}`.",
                s,
            ))
        }
    }
}

impl<K: Ord, Q: Queriable> Queriable for BTreeMap<K, Q> {
    type FieldId = BTreeMapFieldId<K, Q::FieldId>;
    fn query(&self, field_id: &Self::FieldId) -> Option<Field> {
        self.get(field_id.key.as_ref()?)
            .and_then(|f| f.query(&field_id.subquery_id))
    }
}

#[derive(Serialize, Deserialize, below_derive::Queriable)]
pub struct Model {
    #[queriable(ignore)]
    pub time_elapsed: Duration,
    #[queriable(ignore)]
    pub timestamp: SystemTime,
    #[queriable(subquery)]
    pub system: SystemModel,
    #[queriable(subquery)]
    pub cgroup: CgroupModel,
    #[queriable(subquery)]
    pub process: ProcessModel,
    #[queriable(subquery)]
    pub network: NetworkModel,
}

impl Model {
    /// Construct a `Model` from a Sample and optionally, the last
    /// `CumulativeSample` as well as the `Duration` since it was
    /// collected.
    pub fn new(timestamp: SystemTime, sample: &Sample, last: Option<(&Sample, Duration)>) -> Self {
        Model {
            time_elapsed: last.map(|(_, d)| d).unwrap_or_default(),
            timestamp,
            system: SystemModel::new(&sample.system, last.map(|(s, d)| (&s.system, d))),
            cgroup: CgroupModel::new(
                "<root>".to_string(),
                String::new(),
                0,
                &sample.cgroup,
                last.map(|(s, d)| (&s.cgroup, d)),
            )
            .aggr_top_level_val(),
            process: ProcessModel::new(&sample.processes, last.map(|(s, d)| (&s.processes, d))),
            network: NetworkModel::new(&sample.netstats, last.map(|(s, d)| (&s.netstats, d))),
        }
    }
}

/// Get a sample `Model`. There are no guarantees internal consistency of the
/// model, neither are values in the model supposed to be realistic.
pub fn get_sample_model() -> Model {
    serde_json::from_str(sample_model::SAMPLE_MODEL_JSON)
        .expect("Failed to deserialize sample model JSON")
}

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

    #[test]
    fn test_model_field_ids() {
        // Ensure MODEL_FIELD_IDS is update to date.
        let all_variants = ModelFieldId::all_variant_iter()
            .map(|v| v.to_string())
            .collect::<Vec<_>>();
        assert_eq!(all_variants, field_ids::MODEL_FIELD_IDS);
    }

    #[test]
    fn test_deserialize_sample_model_json() {
        get_sample_model();
    }

    #[derive(Clone, Default, Debug, below_derive::Queriable)]
    pub struct TestModel {
        pub msg: String,
    }

    #[test]
    fn test_vec_field_id() {
        let query_str = "1.msg";
        let query = <VecFieldId<TestModelFieldId>>::from_str(query_str).expect("bad query str");
        assert_eq!(
            query,
            VecFieldId {
                idx: Some(1),
                subquery_id: TestModelFieldId::Msg,
            }
        );
        assert_eq!(query.to_string(), query_str);
    }

    #[test]
    fn test_query_vec() {
        let data = vec![
            TestModel {
                msg: "hello".to_owned(),
            },
            TestModel {
                msg: "world".to_owned(),
            },
        ];
        assert_eq!(
            data.query(&VecFieldId {
                idx: Some(1),
                subquery_id: TestModelFieldId::Msg,
            }),
            Some(Field::Str("world".to_owned()))
        );
    }

    #[test]
    fn test_btreemap_field_id() {
        let query_str = "hello.msg";
        let query = <BTreeMapFieldId<String, TestModelFieldId>>::from_str(query_str)
            .expect("bad query str");
        assert_eq!(
            query,
            BTreeMapFieldId {
                key: Some("hello".to_owned()),
                subquery_id: TestModelFieldId::Msg,
            }
        );
        assert_eq!(query.to_string(), query_str);
    }

    #[test]
    fn test_query_btreemap() {
        let mut data = <BTreeMap<String, TestModel>>::new();
        data.insert(
            "hello".to_owned(),
            TestModel {
                msg: "world".to_owned(),
            },
        );
        data.insert(
            "foo".to_owned(),
            TestModel {
                msg: "bar".to_owned(),
            },
        );
        assert_eq!(
            data.query(&BTreeMapFieldId {
                key: Some("hello".to_owned()),
                subquery_id: TestModelFieldId::Msg,
            }),
            Some(Field::Str("world".to_owned()))
        );
    }

    #[test]
    fn test_query_models() {
        let model = get_sample_model();
        for (field_id, expected) in &[
            (
                "system.hostname",
                Some(Field::Str("hostname.example.com".to_owned())),
            ),
            (
                "cgroup.path:/init.scope/.cpu.usage_pct",
                Some(Field::F64(0.01)),
            ),
            (
                "network.interfaces.eth0.interface",
                Some(Field::Str("eth0".to_owned())),
            ),
            (
                "process.processes.1.comm",
                Some(Field::Str("systemd".to_owned())),
            ),
        ] {
            assert_eq!(
                &model.query(
                    &ModelFieldId::from_str(field_id)
                        .map_err(|e| format!("Failed to parse field id {}: {:?}", field_id, e))
                        .unwrap()
                ),
                expected
            );
        }
    }
}