//! GET /api/oneliners — list oneliners for the authenticated user.
//!
//! Time window is caller-controlled via `?hours=N` (default 16, clamped
//! to [1, MAX_HOURS]). Each entry carries the case-id, the oneliner
//! text (or null if not yet generated), and UTC timestamps for when the
//! case started and when its oneliner was last written.
//!
//! Conditional-GET: the response carries a weak ETag `W/"<unix>-<hours>"`
//! derived from the per-user watermark. Clients that send back a matching
//! `If-None-Match` get `304 Not Modified` without touching the filesystem.
//! The `hours` component is included so a client swapping window sizes
//! does not get a stale 304.

use std::path::{Path, PathBuf};
use std::time::SystemTime;

use axum::extract::{Query, State};
use axum::http::{header, HeaderMap, StatusCode};
use axum::response::{IntoResponse, Response};
use axum::Json;
use doctate_common::oneliners::{OnelinerEntry, OnelinersResponse};
use serde::Deserialize;
use time::format_description::well_known::Rfc3339;
use time::{Duration, OffsetDateTime};
use tracing::warn;

use crate::auth::AuthenticatedUser;
use crate::error::AppError;
use crate::OnelinerWatermark;

const DEFAULT_HOURS: u32 = 16;
const MAX_HOURS: u32 = 168;

#[derive(Deserialize)]
pub struct OnelinersQuery {
    hours: Option<u32>,
}

pub async fn handle_oneliners(
    user: AuthenticatedUser,
    State(watermark): State<OnelinerWatermark>,
    Query(params): Query<OnelinersQuery>,
    headers: HeaderMap,
) -> Result<Response, AppError> {
    let hours = params.hours.unwrap_or(DEFAULT_HOURS).clamp(1, MAX_HOURS);
    let now = OffsetDateTime::now_utc();
    let since = now - Duration::hours(hours as i64);

    let current_watermark = watermark.read().await.get(&user.slug).copied();
    let etag = build_etag(current_watermark, hours);

    if client_has_matching_etag(&headers, &etag) {
        return Ok(not_modified(&etag));
    }

    let oneliners = enumerate_recent_oneliners(&user.data_dir, since).await;
    let body = OnelinersResponse {
        as_of: now.format(&Rfc3339).unwrap_or_default(),
        window_hours: hours,
        oneliners,
    };

    let mut response = Json(body).into_response();
    if let Ok(value) = etag.parse() {
        response.headers_mut().insert(header::ETAG, value);
    }
    Ok(response)
}

fn build_etag(watermark: Option<OffsetDateTime>, hours: u32) -> String {
    let seconds = watermark.map(|t| t.unix_timestamp()).unwrap_or(0);
    format!("W/\"{seconds}-{hours}\"")
}

/// Case-sensitive match against the raw `If-None-Match` header value.
/// No wildcard or comma-split logic — the client is our own code sending
/// back the exact ETag we handed it.
fn client_has_matching_etag(headers: &HeaderMap, etag: &str) -> bool {
    headers
        .get(header::IF_NONE_MATCH)
        .and_then(|v| v.to_str().ok())
        .map(|sent| sent == etag)
        .unwrap_or(false)
}

fn not_modified(etag: &str) -> Response {
    let mut response = StatusCode::NOT_MODIFIED.into_response();
    if let Ok(value) = etag.parse() {
        response.headers_mut().insert(header::ETAG, value);
    }
    response
}

/// Scan `<user_data_dir>/<case_id>/` for cases whose earliest recording
/// sits inside the `[since, now]` window. Returns entries sorted by
/// `created_at` descending (newest first). Soft-deleted cases and
/// non-UUID directories are filtered out.
async fn enumerate_recent_oneliners(
    user_data_dir: &Path,
    since: OffsetDateTime,
) -> Vec<OnelinerEntry> {
    let mut entries: Vec<OnelinerEntry> = Vec::new();
    let Ok(mut cases) = tokio::fs::read_dir(user_data_dir).await else {
        return entries;
    };
    while let Ok(Some(case_entry)) = cases.next_entry().await {
        let case_dir = case_entry.path();
        if !case_dir.is_dir() {
            continue;
        }
        let Some(case_id) = case_dir.file_name().and_then(|s| s.to_str()) else {
            continue;
        };
        if uuid::Uuid::parse_str(case_id).is_err() {
            continue;
        }
        if crate::paths::is_deleted(&case_dir).await {
            continue;
        }

        let Some(created_mtime) = earliest_m4a_mtime(&case_dir).await else {
            continue;
        };
        let created_at = OffsetDateTime::from(created_mtime);
        if created_at < since {
            continue;
        }

        let (oneliner_text, updated_at) = read_oneliner(&case_dir).await;
        let Ok(created_at_str) = created_at.format(&Rfc3339) else {
            warn!(case = %case_dir.display(), "format created_at failed");
            continue;
        };
        let updated_at_str = updated_at.and_then(|t| t.format(&Rfc3339).ok());

        entries.push(OnelinerEntry {
            case_id: case_id.to_owned(),
            oneliner: oneliner_text,
            created_at: created_at_str,
            updated_at: updated_at_str,
        });
    }
    entries.sort_by(|a, b| b.created_at.cmp(&a.created_at));
    entries
}

/// Return the earliest `.m4a` mtime in `case_dir`. `.m4a.failed` counts —
/// a failed recording still marks the birth of the case. Returns None on
/// read errors or empty directories.
async fn earliest_m4a_mtime(case_dir: &Path) -> Option<SystemTime> {
    let mut files = tokio::fs::read_dir(case_dir).await.ok()?;
    let mut earliest: Option<SystemTime> = None;
    while let Ok(Some(entry)) = files.next_entry().await {
        let path: PathBuf = entry.path();
        let Some(name) = path.file_name().and_then(|s| s.to_str()) else {
            continue;
        };
        if !(name.ends_with(".m4a") || name.ends_with(".m4a.failed")) {
            continue;
        }
        let Ok(meta) = entry.metadata().await else {
            continue;
        };
        let Ok(mtime) = meta.modified() else {
            continue;
        };
        earliest = match earliest {
            None => Some(mtime),
            Some(e) if mtime < e => Some(mtime),
            other => other,
        };
    }
    earliest
}

/// Read `oneliner.txt` (trimmed, non-empty) plus its mtime. Missing file
/// yields `(None, None)`.
async fn read_oneliner(case_dir: &Path) -> (Option<String>, Option<OffsetDateTime>) {
    let path = case_dir.join("oneliner.txt");
    let text = tokio::fs::read_to_string(&path)
        .await
        .ok()
        .map(|s| s.trim().to_string())
        .filter(|s| !s.is_empty());
    if text.is_none() {
        return (None, None);
    }
    let mtime = tokio::fs::metadata(&path)
        .await
        .ok()
        .and_then(|m| m.modified().ok())
        .map(OffsetDateTime::from);
    (text, mtime)
}