autumn-web 0.4.0

//! Scheduled task infrastructure.
//!
//! Provides [`TaskInfo`] and [`Schedule`] types used by the `#[scheduled]`
//! macro and `tasks![]` collection macro.
//!
//! Tasks are registered via [`AppBuilder::tasks`](crate::app::AppBuilder::tasks)
//! and run alongside the HTTP server using Tokio timers.

use std::future::Future;
use std::pin::Pin;
use std::time::Duration;

use axum::extract::FromRequestParts;
use serde::{Serialize, de::DeserializeOwned};

use crate::state::AppState;
use crate::{AutumnError, AutumnResult};

/// Handler function type for scheduled tasks.
pub type TaskHandler =
    fn(AppState) -> Pin<Box<dyn Future<Output = crate::AutumnResult<()>> + Send>>;

/// Handler function type for named one-off operational tasks.
pub type OneOffTaskHandler =
    fn(AppState, Vec<String>) -> Pin<Box<dyn Future<Output = AutumnResult<()>> + Send>>;

/// Metadata for a named one-off operational task generated by `#[task]`.
pub struct OneOffTaskInfo {
    /// Name operators pass to `autumn task <name>`.
    pub name: String,
    /// First doc-comment line, used by `autumn task --list`.
    pub description: String,
    /// Handler invoked with fully booted app state and raw CLI args.
    pub handler: OneOffTaskHandler,
}

/// Serializable task metadata printed by `autumn task --list`.
#[derive(Debug, Clone, PartialEq, Eq, Serialize)]
pub struct OneOffTaskListing {
    /// Task name accepted by `autumn task <name>`.
    pub name: String,
    /// First doc-comment line captured by `#[task]`.
    pub description: String,
}

/// Structured CLI arguments for one-off tasks.
///
/// `autumn task cleanup --user-id 42 --dry-run` becomes the query string
/// `user_id=42&dry_run=true`, so this extractor can deserialize the same way
/// `Query<T>` does while keeping task signatures explicit.
pub struct TaskArgs<T>(pub T);

/// Extractor bridge used by generated `#[task]` handlers.
pub trait TaskExtractor: Sized {
    /// Resolve an argument from task request parts and app state.
    fn from_task_parts<'a>(
        parts: &'a mut http::request::Parts,
        state: &'a AppState,
    ) -> Pin<Box<dyn Future<Output = AutumnResult<Self>> + Send + 'a>>;
}

impl<T> TaskExtractor for T
where
    T: FromRequestParts<AppState> + Send,
    T::Rejection: Into<AutumnError> + Send,
{
    fn from_task_parts<'a>(
        parts: &'a mut http::request::Parts,
        state: &'a AppState,
    ) -> Pin<Box<dyn Future<Output = AutumnResult<Self>> + Send + 'a>> {
        Box::pin(async move {
            T::from_request_parts(parts, state)
                .await
                .map_err(Into::into)
        })
    }
}

impl<T, S> FromRequestParts<S> for TaskArgs<T>
where
    T: DeserializeOwned + Send,
    S: Send + Sync,
{
    type Rejection = AutumnError;

    async fn from_request_parts(
        parts: &mut http::request::Parts,
        _state: &S,
    ) -> Result<Self, Self::Rejection> {
        let query = parts.uri.query().unwrap_or_default();
        serde_urlencoded::from_str(query)
            .map(Self)
            .map_err(|error| AutumnError::bad_request_msg(format!("invalid task args: {error}")))
    }
}

/// Metadata for a scheduled task, generated by the `#[scheduled]` macro.
pub struct TaskInfo {
    /// Human-readable task name (for logging and health checks).
    pub name: String,
    /// When/how often to run.
    pub schedule: Schedule,
    /// Whether this task is coordinated fleet-wide or intentionally per-replica.
    pub coordination: TaskCoordination,
    /// The task handler, invoked with a clone of `AppState` each run.
    pub handler: TaskHandler,
}

/// Cross-replica coordination mode for a scheduled task.
#[derive(Debug, Clone, Copy, Default, PartialEq, Eq, Serialize, serde::Deserialize)]
#[serde(rename_all = "snake_case")]
pub enum TaskCoordination {
    /// Run at most once per scheduled tick across the configured scheduler backend.
    #[default]
    Fleet,
    /// Run on every replica, bypassing fleet coordination.
    PerReplica,
}

impl std::fmt::Display for TaskCoordination {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::Fleet => f.write_str("fleet"),
            Self::PerReplica => f.write_str("per_replica"),
        }
    }
}

/// How a scheduled task is triggered.
#[non_exhaustive]
pub enum Schedule {
    /// Run after a fixed delay from the end of the previous run.
    FixedDelay(Duration),
    /// Run on a cron schedule (6-field: sec min hour day month weekday).
    Cron {
        /// The 6-field cron expression (e.g., `"0 * * * * *"` for every minute).
        expression: String,
        /// The timezone for the cron expression (e.g., `"America/New_York"`).
        timezone: Option<String>,
    },
}

impl std::fmt::Display for Schedule {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::FixedDelay(d) => write!(f, "every {}s", d.as_secs()),
            Self::Cron { expression, .. } => write!(f, "cron {expression}"),
        }
    }
}

/// Parse a human-readable duration string like `"5m"`, `"1h 30m"`.
///
/// Supported units: `s` (seconds), `m` (minutes), `h` (hours), `d` (days).
///
/// # Errors
///
/// Returns `None` if the string contains invalid syntax.
#[must_use]
pub fn parse_duration(s: &str) -> Option<Duration> {
    let mut total_secs = 0u64;
    let mut current_num = String::new();

    for ch in s.chars() {
        if ch.is_ascii_digit() {
            current_num.push(ch);
        } else if ch.is_ascii_alphabetic() {
            let num: u64 = current_num.parse().ok()?;
            current_num.clear();
            match ch {
                's' => total_secs = total_secs.checked_add(num)?,
                'm' => total_secs = total_secs.checked_add(num.checked_mul(60)?)?,
                'h' => total_secs = total_secs.checked_add(num.checked_mul(3600)?)?,
                'd' => total_secs = total_secs.checked_add(num.checked_mul(86400)?)?,
                _ => return None,
            }
        } else if ch == ' ' {
            // Skip spaces between components
        } else {
            return None;
        }
    }

    if !current_num.is_empty() {
        return None; // Trailing number without unit
    }

    if total_secs == 0 {
        return None;
    }

    Some(Duration::from_secs(total_secs))
}

/// Convert raw `autumn task` arguments to a query string for task extractors.
///
/// Long flags are converted to `snake_case` field names. A flag with no explicit
/// value is treated as a boolean `true`.
///
/// # Errors
///
/// Returns [`AutumnError`] when an argument is not a `--long-flag`.
pub fn task_args_to_query(args: &[String]) -> AutumnResult<String> {
    let mut serializer = url::form_urlencoded::Serializer::new(String::new());
    let mut i = 0;
    while i < args.len() {
        let token = &args[i];
        let Some(flag) = token.strip_prefix("--") else {
            return Err(AutumnError::bad_request_msg(format!(
                "unexpected positional argument {token:?}; task args must use --flag value syntax"
            )));
        };
        if flag.is_empty() {
            return Err(AutumnError::bad_request_msg(
                "empty task argument flag is not allowed",
            ));
        }

        let (key, value) = if let Some((key, value)) = flag.split_once('=') {
            (key, value.to_owned())
        } else if args.get(i + 1).is_some_and(|next| !next.starts_with("--")) {
            i += 1;
            (flag, args[i].clone())
        } else {
            (flag, "true".to_owned())
        };

        serializer.append_pair(&key.replace('-', "_"), &value);
        i += 1;
    }

    Ok(serializer.finish())
}

/// Build request parts used to resolve task extractors.
///
/// # Errors
///
/// Returns [`AutumnError`] when task CLI arguments cannot be represented as a
/// query string or the synthetic URI cannot be built.
pub fn request_parts_for_task_args(args: &[String]) -> AutumnResult<http::request::Parts> {
    let query = task_args_to_query(args)?;
    let uri = if query.is_empty() {
        "/".to_owned()
    } else {
        format!("/?{query}")
    };
    let request = http::Request::builder()
        .uri(uri)
        .body(())
        .map_err(AutumnError::internal_server_error)?;
    Ok(request.into_parts().0)
}

/// Return task metadata sorted by task name.
#[must_use]
pub fn list_one_off_tasks(tasks: &[OneOffTaskInfo]) -> Vec<OneOffTaskListing> {
    let mut listing: Vec<_> = tasks
        .iter()
        .map(|task| OneOffTaskListing {
            name: task.name.clone(),
            description: task.description.clone(),
        })
        .collect();
    listing.sort_by(|a, b| a.name.cmp(&b.name));
    listing
}

/// Validate that every registered one-off task has a unique name.
///
/// # Errors
///
/// Returns a message naming the first duplicate task.
pub fn validate_unique_one_off_task_names(tasks: &[OneOffTaskInfo]) -> Result<(), String> {
    let mut names = std::collections::HashSet::new();
    for task in tasks {
        if !names.insert(task.name.as_str()) {
            return Err(format!("duplicate task name '{}'", task.name));
        }
    }
    Ok(())
}

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

    #[test]
    fn parse_seconds() {
        assert_eq!(parse_duration("5s"), Some(Duration::from_secs(5)));
    }

    #[test]
    fn parse_minutes() {
        assert_eq!(parse_duration("5m"), Some(Duration::from_secs(300)));
    }

    #[test]
    fn parse_hours() {
        assert_eq!(parse_duration("2h"), Some(Duration::from_secs(7200)));
    }

    #[test]
    fn parse_compound() {
        assert_eq!(parse_duration("1h 30m"), Some(Duration::from_secs(5400)));
    }

    #[test]
    fn parse_day() {
        assert_eq!(parse_duration("1d"), Some(Duration::from_secs(86400)));
    }

    #[test]
    fn invalid_unit() {
        assert!(parse_duration("5x").is_none());
    }

    #[test]
    fn trailing_number() {
        assert!(parse_duration("5").is_none());
    }

    #[test]
    fn empty() {
        assert!(parse_duration("").is_none());
    }

    #[test]
    fn zero_duration() {
        assert!(parse_duration("0s").is_none());
        assert!(parse_duration("0m").is_none());
    }

    #[test]
    fn invalid_characters() {
        assert!(parse_duration("1h_30m").is_none());
        assert!(parse_duration("1h-30m").is_none());
    }

    #[test]
    fn multiple_spaces() {
        assert_eq!(parse_duration("1h   30m"), Some(Duration::from_secs(5400)));
    }

    #[test]
    fn compound_trailing_number() {
        assert!(parse_duration("1h 30").is_none());
    }

    #[test]
    fn task_args_to_query_converts_long_flags_to_snake_case_fields() {
        let args = vec![
            "--user-id".to_string(),
            "42".to_string(),
            "--dry-run".to_string(),
        ];

        let query = task_args_to_query(&args).expect("task args should parse");

        assert_eq!(query, "user_id=42&dry_run=true");
    }

    #[tokio::test]
    async fn task_args_extractor_parses_struct_from_cli_style_args() {
        #[derive(Debug, Deserialize, PartialEq, Eq)]
        struct CleanupArgs {
            user_id: i64,
            dry_run: bool,
        }

        let raw = vec![
            "--user-id".to_string(),
            "42".to_string(),
            "--dry-run".to_string(),
        ];
        let mut parts =
            request_parts_for_task_args(&raw).expect("parts should be built from task args");
        let state = AppState::for_test().with_profile("dev");

        let TaskArgs(args) = <TaskArgs<CleanupArgs> as axum::extract::FromRequestParts<
            AppState,
        >>::from_request_parts(&mut parts, &state)
        .await
        .expect("task args should deserialize");

        assert_eq!(
            args,
            CleanupArgs {
                user_id: 42,
                dry_run: true,
            }
        );
    }

    #[test]
    fn task_args_to_query_rejects_values_without_a_flag_name() {
        let error = task_args_to_query(&["42".to_string()])
            .expect_err("bare positional values should be rejected");

        assert!(
            error.to_string().contains("unexpected positional argument"),
            "unexpected error: {error}"
        );
    }

    #[test]
    fn list_one_off_tasks_sorts_by_name_and_keeps_descriptions() {
        fn handler(
            _state: AppState,
            _args: Vec<String>,
        ) -> Pin<Box<dyn Future<Output = AutumnResult<()>> + Send>> {
            Box::pin(async { Ok(()) })
        }

        let tasks = vec![
            OneOffTaskInfo {
                name: "zeta".to_string(),
                description: "Last task".to_string(),
                handler,
            },
            OneOffTaskInfo {
                name: "alpha".to_string(),
                description: "First task".to_string(),
                handler,
            },
        ];

        let listing = list_one_off_tasks(&tasks);

        assert_eq!(listing[0].name, "alpha");
        assert_eq!(listing[0].description, "First task");
        assert_eq!(listing[1].name, "zeta");
        assert_eq!(listing[1].description, "Last task");
    }

    #[test]
    fn validate_unique_one_off_task_names_rejects_duplicates() {
        fn handler(
            _state: AppState,
            _args: Vec<String>,
        ) -> Pin<Box<dyn Future<Output = AutumnResult<()>> + Send>> {
            Box::pin(async { Ok(()) })
        }

        let tasks = vec![
            OneOffTaskInfo {
                name: "cleanup".to_string(),
                description: String::new(),
                handler,
            },
            OneOffTaskInfo {
                name: "cleanup".to_string(),
                description: String::new(),
                handler,
            },
        ];

        let error = validate_unique_one_off_task_names(&tasks)
            .expect_err("duplicate task names should be rejected");

        assert!(error.contains("duplicate task name 'cleanup'"));
    }
}

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

    proptest! {
        #[test]
        fn parse_duration_fuzz_panic(s in "[0-9]{15,30}[smhd]") {
            let _ = parse_duration(&s);
        }
    }
}