//! log: a filtered view of the event journal — everything am did.

use super::*;
use crate::events::{self, Event};
use crate::output::print_json;
use serde::Serialize;

/// Filter journal events: agent, kind list, since date, and a max count.
/// Returns events in reverse chronological order (most recent first).
pub fn filter_events(
    app: &App,
    agent: Option<&str>,
    kinds: Option<&str>,
    since: Option<&str>,
    limit: usize,
) -> Result<Vec<Event>> {
    let mut events = events::read_events(&app.events_dir(), 0);
    if let Some(a) = agent {
        events.retain(|e| e.agent.as_deref() == Some(a));
    }
    if let Some(list) = kinds {
        let wanted: Vec<&str> = list.split(',').map(|s| s.trim()).collect();
        events.retain(|e| wanted.iter().any(|w| e.kind.as_str() == *w));
    }
    if let Some(s) = since {
        let cut = parse_since(s)?;
        events.retain(|e| {
            chrono::DateTime::parse_from_rfc3339(&e.ts)
                .map(|t| t >= cut)
                .unwrap_or(false)
        });
    }
    events.reverse(); // most recent first
    events.truncate(limit);
    Ok(events)
}

/// Live view: print matching events as they arrive (issue #38).
fn follow_loop(app: &App, agent: Option<&str>, kinds: Option<&str>, since: Option<&str>) -> Result<i32> {
    app.log.info("following the journal (Ctrl-C to stop)");
    let mut seen: usize = 0;
    loop {
        let events = filter_events(app, agent, kinds, since, 200)?;
        let mut rendered = String::new();
        for e in events.iter().rev() {
            rendered.push_str(&e.ts);
            rendered.push(' ');
            rendered.push_str(e.kind.as_str());
            if let Some(a) = &e.agent {
                rendered.push(' ');
                rendered.push_str(a);
            }
            rendered.push('\n');
        }
        let bytes = rendered.as_bytes();
        if bytes.len() > seen {
            print!("{}", text_after(&rendered, seen));
            use std::io::Write;
            let _ = std::io::stdout().flush();
        }
        seen = bytes.len();
        std::thread::sleep(std::time::Duration::from_secs(1));
    }
}

pub fn parse_since(s: &str) -> Result<chrono::DateTime<chrono::FixedOffset>> {
    if let Ok(t) = chrono::DateTime::parse_from_rfc3339(s) {
        return Ok(t);
    }
    chrono::NaiveDate::parse_from_str(s, "%Y-%m-%d")
        .map_err(|_| anyhow!("invalid date '{s}' — expected YYYY-MM-DD or an RFC 3339 timestamp"))?
        .and_hms_opt(0, 0, 0)
        .map(|d| chrono::DateTime::from_naive_utc_and_offset(d, chrono::FixedOffset::east_opt(0).unwrap()))
        .ok_or_else(|| anyhow!("invalid date '{s}'"))
}

#[derive(Serialize)]
pub struct LogRow {
    pub ts: String,
    pub kind: String,
    pub agent: Option<String>,
    pub pid: Option<u32>,
    pub exit_code: Option<i32>,
    pub duration_s: Option<u64>,
    pub session: Option<String>,
}

impl From<&Event> for LogRow {
    fn from(e: &Event) -> Self {
        LogRow {
            ts: e.ts.clone(),
            kind: e.kind.as_str().to_string(),
            agent: e.agent.clone(),
            pid: e.pid,
            exit_code: e.exit_code,
            duration_s: e.duration_s,
            session: e.session.clone(),
        }
    }
}

/// Rows for the web API (issue #54): same shape as `am log --json`.
pub fn rows(
    app: &App,
    agent: Option<&str>,
    kinds: Option<&str>,
    since: Option<&str>,
    limit: usize,
) -> Result<Vec<LogRow>> {
    Ok(filter_events(app, agent, kinds, since, limit)?
        .iter()
        .map(LogRow::from)
        .collect())
}

/// Chars of text after byte offset seen (UTF-8 safe).
pub fn text_after(text: &str, seen: usize) -> String {
    text.char_indices()
        .filter(|(i, _)| *i >= seen)
        .map(|(_, c)| c)
        .collect()
}

pub fn run(
    app: &App,
    agent: Option<&str>,
    kinds: Option<&str>,
    since: Option<&str>,
    limit: usize,
    follow: bool,
) -> Result<i32> {
    if follow {
        return follow_loop(app, agent, kinds, since);
    }
    let events = filter_events(app, agent, kinds, since, limit)?;
    if app.json() {
        let rows: Vec<LogRow> = events.iter().map(LogRow::from).collect();
        print_json(&rows);
        return Ok(0);
    }
    for e in &events {
        let mut parts = vec![e.ts.clone(), e.kind.as_str().to_string()];
        if let Some(a) = &e.agent {
            parts.push(a.clone());
        }
        if let Some(p) = e.pid {
            parts.push(format!("pid={p}"));
        }
        if let Some(c) = e.exit_code {
            parts.push(format!("exit={c}"));
        }
        if let Some(d) = e.duration_s {
            parts.push(format!("dur={d}s"));
        }
        println!("{}", parts.join(" "));
    }
    if events.is_empty() {
        app.log.info("no matching events in the journal");
    }
    Ok(0)
}

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

    #[test]
    fn parse_since_accepts_date_and_timestamp() {
        let d = parse_since("2026-08-01").unwrap();
        assert_eq!(d.format("%Y-%m-%d").to_string(), "2026-08-01");
        assert!(parse_since("2026-08-01T00:00:00Z").is_ok());
        assert!(parse_since("hier").is_err());
    }
}