//! TRACES: FR-UI-8
//! Reading and writing the place — where the photographer was.
//!
//! The record itself is [`dr_types::Place`], which is where the reasoning about
//! what a place *is* lives: why it is not a setting, why it names photographs by
//! remote path and collections by UUID rather than by any local integer, and why
//! the newer of two records simply wins. This module is the half that touches a
//! disk, split off for the reason `dr-types`' manifest gives about
//! `settings.json`: a JSON serialiser in `core/` would be paid for by every
//! crate there.
//!
//! A near-twin of [`crate::settings_store`] in shape, and deliberately not an
//! extension of it. Two files, two lifetimes — signing out forgets a session and
//! must not discard a cache budget; resetting preferences must not forget where
//! you were.

use std::path::PathBuf;

use dr_types::{Place, StoredFilter};

use crate::library::{PeopleMode, RatingFilter};

impl From<&RatingFilter> for StoredFilter {
    fn from(f: &RatingFilter) -> Self {
        Self {
            min_rating: f.min_rating,
            max_rating: f.max_rating,
            unjudged: f.unjudged,
            flag: f.flag,
            local_only: f.local_only,
            captured_from: f.captured_from,
            captured_to: f.captured_to,
            people: f.people.clone(),
            people_all: matches!(f.people_mode, PeopleMode::All),
            eyes_open: f.eyes_open,
            label: f.label,
        }
    }
}

impl From<&StoredFilter> for RatingFilter {
    fn from(s: &StoredFilter) -> Self {
        Self {
            min_rating: s.min_rating,
            max_rating: s.max_rating.map(|m| m.min(5)),
            unjudged: s.unjudged,
            flag: s.flag,
            local_only: s.local_only,
            captured_from: s.captured_from,
            captured_to: s.captured_to,
            people: s.people.clone(),
            people_mode: if s.people_all {
                PeopleMode::All
            } else {
                PeopleMode::Any
            },
            eyes_open: s.eyes_open,
            label: s.label,
        }
    }
}

/// Parse a record as it travels — the body of the file, local or remote.
///
/// `None` rather than an error for anything unreadable. A place is advisory:
/// the only thing lost by discarding one is that the grid opens at the top, and
/// an application that refused to start because a position file was truncated
/// would be trading a certainty for an inconvenience. The failure is logged so
/// it is not silent.
pub fn from_bytes(bytes: &[u8], whence: &str) -> Option<Place> {
    match serde_json::from_slice::<Place>(bytes) {
        Ok(p) => Some(p),
        Err(e) => {
            log::warn!("{whence} is not a readable place ({e}); ignoring it");
            None
        }
    }
}

/// The bytes that travel, local file and server copy alike.
pub fn to_bytes(place: &Place) -> Result<Vec<u8>, serde_json::Error> {
    serde_json::to_vec_pretty(place)
}

/// Loads and saves the place, beside the catalog it belongs to.
///
/// One file per library rather than one file holding every library's place,
/// because that is how everything else per-account is stored — the catalog, the
/// thumbnail shards, the un-uploaded sidecars all hang off
/// `Account::namespace()` — and because the file that travels to the server has
/// to be exactly one library's anyway. A map would need splitting on the way
/// out and merging on the way in, for no gain.
///
/// In the *data* directory, not the cache one. `library::place_path` explains
/// why that distinction is load-bearing on Android; here it matters less —
/// losing a place costs a scroll — but a file that sat in a directory the
/// system deletes at will would be one that never survived to be useful.
pub struct PlaceStore {
    path: PathBuf,
}

impl PlaceStore {
    pub fn open_at(path: PathBuf) -> Self {
        Self { path }
    }

    /// The stored place, or `None` if there is not one.
    ///
    /// A missing file is a first run, not a failure, and neither is an
    /// unparseable one — see [`from_bytes`].
    pub fn load(&self) -> Option<Place> {
        match std::fs::read(&self.path) {
            Ok(bytes) => from_bytes(&bytes, &self.path.display().to_string()),
            Err(e) if e.kind() == std::io::ErrorKind::NotFound => None,
            Err(e) => {
                log::warn!("reading {}: {e}", self.path.display());
                None
            }
        }
    }

    /// Write it, creating the directory if the account is new.
    ///
    /// Errors are logged and swallowed. This is called from a scroll settling,
    /// and a photographer cannot act on "the place could not be written" — the
    /// next scroll writes it again, and if the disk is genuinely gone there are
    /// louder failures already on screen.
    pub fn save(&self, place: &Place) {
        if let Some(dir) = self.path.parent() {
            if let Err(e) = std::fs::create_dir_all(dir) {
                log::warn!("creating {}: {e}", dir.display());
                return;
            }
        }
        let bytes = match to_bytes(place) {
            Ok(b) => b,
            Err(e) => {
                log::warn!("serialising the place: {e}");
                return;
            }
        };
        if let Err(e) = std::fs::write(&self.path, bytes) {
            log::warn!("writing {}: {e}", self.path.display());
        }
    }

    /// Take a record only if it is newer than what is here.
    ///
    /// The one operation the sync needs on the way in, and it is written here
    /// rather than at the call site so that "newer wins" has exactly one
    /// spelling. Returns whether the stored record changed.
    pub fn adopt(&self, incoming: &Place) -> bool {
        if !incoming.supersedes(self.load().as_ref()) {
            return false;
        }
        self.save(incoming);
        true
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use dr_types::{PlaceScope, Screen};

    fn dir(name: &str) -> PathBuf {
        let d = std::env::temp_dir().join(format!("darkroom-place-test-{name}"));
        let _ = std::fs::remove_dir_all(&d);
        std::fs::create_dir_all(&d).unwrap();
        d
    }

    fn a_place(at: i64) -> Place {
        Place {
            at,
            device: "desktop".into(),
            screen: Screen::Develop,
            scope: PlaceScope::Collection {
                uuid: "0d1f-…-9c".into(),
            },
            path: "2019/2019-04-03/DSC_1234.NEF".into(),
            captured_at: Some(1_554_300_000),
            filter: StoredFilter {
                min_rating: 3,
                max_rating: None,
                unjudged: false,
                flag: Some(dr_types::FlagState::Pick),
                local_only: true,
                captured_from: Some(1),
                captured_to: Some(2),
                people: vec![7, 9],
                people_all: true,
                eyes_open: true,
                label: Some(dr_types::ColourLabel::Green),
            },
        }
    }

    #[test]
    fn round_trips_through_the_file() {
        let store = PlaceStore::open_at(dir("round-trip").join("place.json"));
        let place = a_place(1000);
        store.save(&place);
        assert_eq!(store.load(), Some(place));
    }

    #[test]
    fn a_missing_file_is_a_first_run() {
        let store = PlaceStore::open_at(dir("missing").join("place.json"));
        assert_eq!(store.load(), None);
    }

    #[test]
    fn the_directory_is_created_on_the_way_out() {
        // A first launch against a new account has no data directory yet, and
        // the place is written before anything else in it has been.
        let store = PlaceStore::open_at(dir("mkdir").join("deep").join("er").join("place.json"));
        store.save(&a_place(1));
        assert!(store.load().is_some());
    }

    #[test]
    fn a_torn_file_is_ignored_rather_than_fatal() {
        let path = dir("torn").join("place.json");
        std::fs::write(&path, b"{\"at\": 12, \"screen\":").unwrap();
        let store = PlaceStore::open_at(path);
        assert_eq!(store.load(), None, "and the app opens at the top instead");
    }

    #[test]
    fn a_file_from_a_newer_build_keeps_what_it_can() {
        // The additive-change contract: a field this build does not know must
        // not cost it the fields it does.
        let path = dir("newer").join("place.json");
        std::fs::write(
            &path,
            br#"{"at": 42, "path": "a/b.NEF", "zoom_level": 3, "screen": "develop"}"#,
        )
        .unwrap();
        let got = PlaceStore::open_at(path).load().expect("still readable");
        assert_eq!(got.at, 42);
        assert_eq!(got.path, "a/b.NEF");
        assert_eq!(got.screen, Screen::Develop);
    }

    #[test]
    fn a_file_from_an_older_build_defaults_what_is_missing() {
        let path = dir("older").join("place.json");
        std::fs::write(&path, br#"{"at": 42, "path": "a/b.NEF"}"#).unwrap();
        let got = PlaceStore::open_at(path).load().expect("still readable");
        assert_eq!(got.screen, Screen::Library, "the safe view to arrive in");
        assert_eq!(got.scope, PlaceScope::Library);
        assert_eq!(got.filter, StoredFilter::default());
    }

    #[test]
    fn the_newer_record_wins_in_both_directions() {
        let older = a_place(100);
        let newer = a_place(200);
        assert!(newer.supersedes(Some(&older)));
        assert!(!older.supersedes(Some(&newer)));
        assert!(older.supersedes(None), "anything beats nothing");
    }

    #[test]
    fn an_equal_timestamp_settles_rather_than_ping_pongs() {
        // Two idle devices re-reading the same record must not each decide they
        // have something to say.
        let place = a_place(100);
        assert!(!place.supersedes(Some(&place.clone())));
    }

    #[test]
    fn adopt_takes_only_what_is_newer() {
        let store = PlaceStore::open_at(dir("adopt").join("place.json"));
        store.save(&a_place(200));

        let mut stale = a_place(100);
        stale.path = "somewhere/else.NEF".into();
        assert!(!store.adopt(&stale));
        assert_eq!(store.load().unwrap().at, 200, "ours is untouched");

        let mut fresh = a_place(300);
        fresh.path = "somewhere/else.NEF".into();
        assert!(store.adopt(&fresh));
        assert_eq!(store.load().unwrap().path, "somewhere/else.NEF");
    }

    #[test]
    fn a_record_from_another_device_is_taken_on_its_timestamp_alone() {
        // `device` is for reading the file, not for resolving a conflict: a
        // handover from the tablet is exactly the case this feature exists for,
        // and preferring our own record would defeat it.
        let store = PlaceStore::open_at(dir("device").join("place.json"));
        store.save(&a_place(100));

        let mut theirs = a_place(101);
        theirs.device = "tablet".into();
        assert!(store.adopt(&theirs));
        assert_eq!(store.load().unwrap().device, "tablet");
    }

    #[test]
    fn the_filter_survives_the_projection() {
        // The record and the query must narrow the grid by the same thing, or a
        // restored place shows a different set than the one that was left.
        let original = RatingFilter {
            min_rating: 4,
            max_rating: Some(4),
            unjudged: true,
            flag: Some(dr_types::FlagState::Reject),
            local_only: true,
            captured_from: Some(10),
            captured_to: Some(20),
            people: vec![3, 5, 8],
            people_mode: PeopleMode::All,
            eyes_open: true,
            label: Some(dr_types::ColourLabel::Purple),
        };
        let back: RatingFilter = (&StoredFilter::from(&original)).into();
        assert_eq!(back, original);

        let empty = RatingFilter::default();
        let back: RatingFilter = (&StoredFilter::from(&empty)).into();
        assert_eq!(back, empty);
        assert!(back.is_unfiltered());
    }

    #[test]
    fn a_record_from_before_star_ranges_has_no_ceiling() {
        // TRACES: FR-UI-5
        // Another device on an older build writes records without the field.
        let old: StoredFilter = serde_json::from_str(r#"{"min_rating":2}"#).unwrap();
        let back: RatingFilter = (&old).into();
        assert_eq!((back.min_rating, back.max_rating), (2, None));
    }

    #[test]
    fn a_scope_travels_as_a_uuid() {
        // The guard against someone reaching for `collections.id`, which the
        // schema calls local and colliding across devices.
        let json = serde_json::to_string(&PlaceScope::Collection {
            uuid: "abc-123".into(),
        })
        .unwrap();
        assert!(json.contains("abc-123"), "{json}");
        assert_eq!(
            serde_json::from_str::<PlaceScope>(&json).unwrap(),
            PlaceScope::Collection {
                uuid: "abc-123".into()
            }
        );
    }

    #[test]
    fn the_trash_is_its_own_scope() {
        let json = serde_json::to_string(&PlaceScope::Trash).unwrap();
        assert_eq!(
            serde_json::from_str::<PlaceScope>(&json).unwrap(),
            PlaceScope::Trash
        );
    }
}