#![deny(missing_docs)]

//! # Background Jobs Core
//! _basic types and traits for implementing a background jobs processor_
//!
//! This crate shouldn't be depended on directly, except in the case of implementing a custom jobs
//! processor. For a default solution based on Actix and Sled, look at the `background-jobs` crate.

use anyhow::Error;

#[cfg(feature = "with-actix")]
mod actix_job;
mod job;
mod job_info;
mod processor_map;
mod stats;
mod storage;

pub use crate::{
    job::{new_job, new_scheduled_job, process, Job},
    job_info::{JobInfo, NewJobInfo, ReturnJobInfo},
    processor_map::{CachedProcessorMap, ProcessorMap},
    stats::{JobStat, Stats},
    storage::{memory_storage, Storage},
};

#[cfg(feature = "with-actix")]
pub use actix_job::ActixJob;

#[derive(Debug, thiserror::Error)]
/// The error type returned by the `process` method
pub enum JobError {
    /// Some error occurred while processing the job
    #[error("Error performing job: {0}")]
    Processing(#[from] Error),

    /// Creating a `Job` type from the provided `serde_json::Value` failed
    #[error("Could not make JSON value from arguments")]
    Json,

    /// This job type was not registered for this client
    #[error("This job type was not registered for the client")]
    Unregistered,
}

#[derive(Clone, Debug, Eq, PartialEq, serde::Deserialize, serde::Serialize)]
/// Indicate the state of a job after an attempted run
pub enum JobResult {
    /// The job succeeded
    Success,

    /// The job failed
    Failure,

    /// The worker had no concept of this job
    Unregistered,

    /// The worker requesting this job closed
    Unexecuted,
}

impl JobResult {
    /// Indicate a successful job
    pub fn success() -> Self {
        JobResult::Success
    }

    /// Indicate a failed job
    pub fn failure() -> Self {
        JobResult::Failure
    }

    /// Indicate that the job was not registered for this worker
    pub fn unregistered() -> Self {
        JobResult::Unregistered
    }

    /// Check if the job failed
    pub fn is_failure(&self) -> bool {
        *self == JobResult::Failure
    }

    /// Check if the job succeeded
    pub fn is_success(&self) -> bool {
        *self == JobResult::Success
    }

    /// Check if the job is missing it's processor
    pub fn is_unregistered(&self) -> bool {
        *self == JobResult::Unregistered
    }

    /// Check if the job was returned without an execution attempt
    pub fn is_unexecuted(&self) -> bool {
        *self == JobResult::Unexecuted
    }
}

#[derive(Clone, Debug, Eq, PartialEq, serde::Deserialize, serde::Serialize)]
/// Set the status of a job when storing it
pub enum JobStatus {
    /// Job should be queued
    Pending,

    /// Job is running
    Running,
}

impl JobStatus {
    /// The job should be queued
    pub fn pending() -> Self {
        JobStatus::Pending
    }

    /// The job is running
    pub fn running() -> Self {
        JobStatus::Running
    }

    /// Check if the job is ready to be queued
    pub fn is_pending(&self) -> bool {
        *self == JobStatus::Pending
    }

    /// Check if the job is running
    pub fn is_running(&self) -> bool {
        *self == JobStatus::Running
    }
}

impl std::fmt::Display for JobStatus {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        match self {
            JobStatus::Pending => write!(f, "Pending"),
            JobStatus::Running => write!(f, "Running"),
        }
    }
}

#[derive(Clone, Debug, Default, Eq, Hash, Ord, PartialEq, PartialOrd, thiserror::Error)]
#[error("Invalid job status")]
/// The error generated when parsing a job's status if it's not 'Pending' or 'Running'
pub struct JobStatusError;

impl std::str::FromStr for JobStatus {
    type Err = JobStatusError;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        match s {
            "Pending" => Ok(JobStatus::Pending),
            "Running" => Ok(JobStatus::Running),
            _ => Err(JobStatusError),
        }
    }
}

#[derive(Clone, Debug, Eq, PartialEq, serde::Deserialize, serde::Serialize)]
/// Different styles for retrying jobs
pub enum Backoff {
    /// Seconds between execution
    ///
    /// For example, `Backoff::Linear(5)` will retry a failed job 5 seconds after the previous
    /// attempt
    Linear(usize),

    /// Base for seconds between execution
    ///
    /// For example, `Backoff::Exponential(2)` will retry a failed job 2 seconds after the first
    /// failure, 4 seconds after the second failure, 8 seconds after the third failure, and 16
    /// seconds after the fourth failure
    Exponential(usize),
}

#[derive(Clone, Debug, Eq, PartialEq, serde::Deserialize, serde::Serialize)]
/// How many times a job should be retried before giving up
pub enum MaxRetries {
    /// Keep retrying forever
    Infinite,

    /// Put a limit on the number of retries
    Count(usize),
}

impl MaxRetries {
    fn compare(&self, retry_count: u32) -> ShouldStop {
        match *self {
            MaxRetries::Infinite => ShouldStop::Requeue,
            MaxRetries::Count(ref count) => {
                if (retry_count as usize) <= *count {
                    ShouldStop::Requeue
                } else {
                    ShouldStop::LimitReached
                }
            }
        }
    }
}

#[derive(Clone, Debug, Eq, PartialEq)]
/// A type that represents whether a job should be requeued
pub enum ShouldStop {
    /// The job has hit the maximum allowed number of retries, and should be failed permanently
    LimitReached,

    /// The job is allowed to be put back into the job queue
    Requeue,
}

impl ShouldStop {
    /// A boolean representation of this state
    pub fn should_requeue(&self) -> bool {
        *self == ShouldStop::Requeue
    }
}

impl From<serde_json::error::Error> for JobError {
    fn from(_: serde_json::error::Error) -> Self {
        JobError::Json
    }
}