/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

use parking_lot::Mutex;

static RECENT_BREADCRUMBS: Mutex<BreadcrumbRingBuffer> = Mutex::new(BreadcrumbRingBuffer::new());

pub fn report_error_to_app(type_name: String, message: String) {
    // Report errors by sending a tracing event to the `app-services-error-reporter::error` target.
    //
    // Applications should register for these events and send a glean error ping when they occur.
    //
    // breadcrumbs will be sent in the `breadcrumbs` field as a single string, with each individual
    // breadcrumb joined by newlines.
    let breadcrumbs = RECENT_BREADCRUMBS.lock().get_breadcrumbs().join("\n");
    tracing_support::error!(target: "app-services-error-reporter::error", message, type_name, breadcrumbs);
}

pub fn report_breadcrumb(message: String, module: String, line: u32, column: u32) {
    // When we see a breadcrumb:
    //   - Push it to the `RECENT_BREADCRUMBS` list
    //   - Send out the `app-services-error-reporter::breadcrumb`.  Applications can register for
    //     these events and log them.
    RECENT_BREADCRUMBS.lock().push(message.clone());
    tracing_support::info!(target: "app-services-error-reporter::breadcrumb", message, module, line, column);
}

/// Ring buffer implementation that we use to store the most recent 20 breadcrumbs
#[derive(Default)]
struct BreadcrumbRingBuffer {
    breadcrumbs: Vec<String>,
    pos: usize,
}

impl BreadcrumbRingBuffer {
    const MAX_ITEMS: usize = 20;

    const fn new() -> Self {
        Self {
            breadcrumbs: Vec::new(),
            pos: 0,
        }
    }

    fn push(&mut self, breadcrumb: impl Into<String>) {
        let breadcrumb = breadcrumb.into();
        if self.breadcrumbs.len() < Self::MAX_ITEMS {
            self.breadcrumbs.push(breadcrumb);
        } else {
            self.breadcrumbs[self.pos] = breadcrumb;
            self.pos = (self.pos + 1) % Self::MAX_ITEMS;
        }
    }

    fn get_breadcrumbs(&self) -> Vec<String> {
        let mut breadcrumbs = Vec::from(&self.breadcrumbs[self.pos..]);
        breadcrumbs.extend(self.breadcrumbs[..self.pos].iter().map(|s| s.to_string()));
        breadcrumbs
    }
}

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

    #[test]
    fn test_buffer() {
        let mut buf = BreadcrumbRingBuffer::default();
        buf.push("00");
        buf.push("01");
        buf.push("02");
        buf.push("03");
        buf.push("04");
        buf.push("05");
        buf.push("06");
        buf.push("07");
        buf.push("08");
        buf.push("09");
        assert_eq!(
            buf.get_breadcrumbs(),
            vec![
                "00".to_string(),
                "01".to_string(),
                "02".to_string(),
                "03".to_string(),
                "04".to_string(),
                "05".to_string(),
                "06".to_string(),
                "07".to_string(),
                "08".to_string(),
                "09".to_string(),
            ]
        );

        buf.push("10");
        buf.push("11");
        buf.push("12");
        buf.push("13");
        buf.push("14");
        buf.push("15");
        buf.push("16");
        buf.push("17");
        buf.push("18");
        buf.push("19");
        assert_eq!(
            buf.get_breadcrumbs(),
            vec![
                "00".to_string(),
                "01".to_string(),
                "02".to_string(),
                "03".to_string(),
                "04".to_string(),
                "05".to_string(),
                "06".to_string(),
                "07".to_string(),
                "08".to_string(),
                "09".to_string(),
                "10".to_string(),
                "11".to_string(),
                "12".to_string(),
                "13".to_string(),
                "14".to_string(),
                "15".to_string(),
                "16".to_string(),
                "17".to_string(),
                "18".to_string(),
                "19".to_string(),
            ]
        );

        buf.push("20");
        assert_eq!(
            buf.get_breadcrumbs(),
            vec![
                "01".to_string(),
                "02".to_string(),
                "03".to_string(),
                "04".to_string(),
                "05".to_string(),
                "06".to_string(),
                "07".to_string(),
                "08".to_string(),
                "09".to_string(),
                "10".to_string(),
                "11".to_string(),
                "12".to_string(),
                "13".to_string(),
                "14".to_string(),
                "15".to_string(),
                "16".to_string(),
                "17".to_string(),
                "18".to_string(),
                "19".to_string(),
                "20".to_string(),
            ]
        );

        buf.push("21");
        buf.push("22");
        buf.push("23");
        buf.push("24");
        buf.push("25");
        assert_eq!(
            buf.get_breadcrumbs(),
            vec![
                "06".to_string(),
                "07".to_string(),
                "08".to_string(),
                "09".to_string(),
                "10".to_string(),
                "11".to_string(),
                "12".to_string(),
                "13".to_string(),
                "14".to_string(),
                "15".to_string(),
                "16".to_string(),
                "17".to_string(),
                "18".to_string(),
                "19".to_string(),
                "20".to_string(),
                "21".to_string(),
                "22".to_string(),
                "23".to_string(),
                "24".to_string(),
                "25".to_string(),
            ]
        );
    }
}