//! Pushing local judgements out to XMP sidecars, and reloading sidecars a
//! person chose to trust by hand.

use crate::executors::{self, Executor};
use dr_catalog::Catalog;
use dr_sync::{Connection, RemoteBackend, RemoteId, RemotePath};
use std::path::PathBuf;
use std::sync::mpsc::Receiver;

/// TRACES: FR-CAT-13 | NFR-R4
/// One image's ratings, label and keywords, on their way to the `.xmp`
/// beside it.
///
/// Distinct from [`SidecarWrite`], which amends DarkRoom's own document
/// through the cache and the outbox. This is best-effort in the other
/// direction: the catalog and the `.drsc` are authoritative, the `.xmp` is a
/// courtesy to whatever else reads the folder, and a write that cannot
/// happen now is written again — from the catalog, whole — the next time
/// anything about the photograph is judged. So nothing is queued.
#[derive(Debug, Clone)]
pub struct XmpWrite {
    pub image_path: String,
    pub record: dr_xmp::Xmp,
}

/// TRACES: FR-CAT-13 | NFR-R4
/// Write each record into the XMP sidecar beside its image.
///
/// An existing sidecar of either spelling is rewritten in place, which is the
/// whole point of `dr_xmp::rewrite`: only the properties DarkRoom owns move,
/// and another application's settings, comments and namespaces come through
/// byte for byte. A photograph with neither gets a new file under Lightroom's
/// name. Reported once at the end, as the judgement writes are.
pub fn spawn_xmp_writes(conn: Connection, writes: Vec<XmpWrite>) -> Receiver<XmpMessage> {
    let (tx, rx) = std::sync::mpsc::channel();
    executors::spawn(Executor::Network, "xmp-write", move || {
        let mut written = 0usize;
        let mut failed = 0usize;
        let mut last_error = None;
        let rt = match crate::net_runtime::build() {
            Ok(rt) => rt,
            Err(e) => {
                let _ = tx.send(XmpMessage::Finished {
                    written: 0,
                    failed: writes.len(),
                    last_error: Some(e.to_string()),
                });
                return;
            }
        };
        rt.block_on(async {
            let backend = match crate::remote::connect(&conn) {
                Ok(b) => b,
                Err(e) => {
                    failed = writes.len();
                    last_error = Some(e.to_string());
                    return;
                }
            };
            for w in &writes {
                match write_one_xmp(&*backend, w).await {
                    Ok(()) => written += 1,
                    Err(e) => {
                        log::warn!("xmp sidecar for {}: {e}", w.image_path);
                        last_error = Some(e);
                        failed += 1;
                    }
                }
            }
        });
        let _ = tx.send(XmpMessage::Finished {
            written,
            failed,
            last_error,
        });
    });
    rx
}

/// The outcome of a batch of XMP writes.
#[derive(Debug)]
pub enum XmpMessage {
    Finished {
        written: usize,
        failed: usize,
        last_error: Option<String>,
    },
}

/// Read-modify-write one image's XMP sidecar on the server.
pub(super) async fn write_one_xmp(backend: &dyn RemoteBackend, w: &XmpWrite) -> Result<(), String> {
    let [darktable, lightroom] = crate::xmp_sync::candidate_paths(&w.image_path);
    // Whichever exists is the one rewritten; neither existing means the
    // Lightroom spelling is created. An existing file this build cannot
    // parse is left alone rather than replaced — it is somebody else's
    // document, and a refusal is recoverable where an overwrite is not.
    let mut target = lightroom.clone();
    let mut existing: Option<String> = None;
    for path in [&darktable, &lightroom] {
        if let Ok(bytes) = backend
            .get(&RemoteId::Path(RemotePath::new(path.clone())), None)
            .await
        {
            if !bytes.is_empty() {
                target = path.clone();
                existing = Some(String::from_utf8_lossy(&bytes).into_owned());
                break;
            }
        }
    }
    let text = match existing {
        Some(text) => {
            // The file's caption, copyright and hierarchy come through: the
            // catalog has nowhere to keep them, and a rewrite that said
            // nothing about them would remove them.
            let theirs = dr_xmp::Xmp::parse(&text)
                .map_err(|e| format!("{target} is not a sidecar this build can read: {e}"))?;
            let mut record = w.record.clone();
            crate::xmp_sync::carry_through(&mut record, &theirs);
            record
                .rewrite(&text)
                .map_err(|e| format!("{target} is not a sidecar this build can rewrite: {e}"))?
        }
        None => w.record.to_text(),
    };
    backend
        .put(&RemotePath::new(target), text.into_bytes(), None)
        .await
        .map(|_| ())
        .map_err(|e| e.to_string())
}

/// TRACES: FR-CAT-13
/// The offered reload: re-read the sidecars a person chose to trust, with
/// the sidecar winning. One fetch per path, the catalog opened on this
/// thread as the scan opens it.
pub fn spawn_xmp_reload(
    conn: Connection,
    root: String,
    catalog_path: PathBuf,
    paths: Vec<String>,
) -> Receiver<XmpMessage> {
    let (tx, rx) = std::sync::mpsc::channel();
    executors::spawn(Executor::Network, "xmp-reload", move || {
        let mut written = 0usize;
        let mut failed = 0usize;
        let mut last_error = None;
        let outcome: Result<(), String> = (|| {
            let catalog = Catalog::open(&catalog_path).map_err(|e| e.to_string())?;
            let root_id: i64 = catalog
                .connection()
                .query_row(
                    "SELECT id FROM roots WHERE label = ?1 AND kind = 'remote'",
                    [&root],
                    |r| r.get(0),
                )
                .map_err(|e| e.to_string())?;
            let rt = crate::net_runtime::build().map_err(|e| e.to_string())?;
            rt.block_on(async {
                let backend = crate::remote::connect(&conn).map_err(|e| e.to_string())?;
                for path in &paths {
                    let fetched = backend
                        .get(&RemoteId::Path(RemotePath::new(path.clone())), None)
                        .await
                        .map_err(|e| e.to_string())
                        .and_then(|bytes| {
                            let text = String::from_utf8_lossy(&bytes);
                            crate::xmp_sync::reload(catalog.connection(), root_id, path, &text)
                        });
                    match fetched {
                        Ok(taken) => written += taken.changed,
                        Err(e) => {
                            log::warn!("reloading {path}: {e}");
                            last_error = Some(e);
                            failed += 1;
                        }
                    }
                }
                Ok(())
            })
        })();
        if let Err(e) = outcome {
            failed = paths.len();
            last_error = Some(e);
        }
        let _ = tx.send(XmpMessage::Finished {
            written,
            failed,
            last_error,
        });
    });
    rx
}