// The in-process read surface over the local cache (issue #44).
//
// A CLI or an in-process script reads albums, photos, and a grouped timeline
// through `lib.albums`, `lib.photos`, and `lib.timeline`. Every call is
// answered synchronously from the same plain-record projection the GUI reads
// (`deriveRecords`, issue #43); nothing here touches the network. Every method
// takes a single named-argument object.
//
// The `Album` and `Photo` classes are thin, in-process-only wrappers over
// those records: a caller that holds an object reference gets typed field
// access and, for an album, its photos. They are not sent across IPC — the
// plain records are the serializable surface, and `record()` returns one.
// Content-fetch methods (`Photo.original` / `thumbnail`) belong to a later
// unit; this surface is read-only.

import type { CollectionType, FileType } from "../model/types.js";
import type { AlbumRecord, PhotoRecord, DerivedRecords } from "./records.js";

// Newest first, with fileID as a stable tiebreak so equal-timed files order
// deterministically — the same order the record projection uses.
const byNewest = (a: PhotoRecord, b: PhotoRecord): number =>
    b.takenAt - a.takenAt || b.fileID - a.fileID;

// Albums newest updated first, collection id breaking ties. This is the order
// `albums.list` returns and the order `byName` resolves a name collision in.
const byNewestAlbum = (a: AlbumRecord, b: AlbumRecord): number =>
    b.updationTime - a.updationTime || b.collectionID - a.collectionID;

// A single photo. Field access mirrors `PhotoRecord`; `record()` returns the
// underlying plain record for callers that need the IPC-safe value.
export class Photo {
    constructor(private readonly rec: PhotoRecord) {}

    get fileID(): number {
        return this.rec.fileID;
    }
    get albumIDs(): number[] {
        return this.rec.albumIDs;
    }
    get title(): string {
        return this.rec.title;
    }
    get takenAt(): number {
        return this.rec.takenAt;
    }
    get fileType(): FileType {
        return this.rec.fileType;
    }
    get caption(): string | undefined {
        return this.rec.caption;
    }
    get width(): number | undefined {
        return this.rec.width;
    }
    get height(): number | undefined {
        return this.rec.height;
    }
    get latitude(): number | undefined {
        return this.rec.latitude;
    }
    get longitude(): number | undefined {
        return this.rec.longitude;
    }
    get isArchived(): boolean {
        return this.rec.isArchived;
    }
    get isHidden(): boolean {
        return this.rec.isHidden;
    }

    record(): PhotoRecord {
        return this.rec;
    }
}

// A single album. `photos.list()` returns the album's photos as wrappers,
// newest first (the record already stores `fileIDs` in that order).
export class Album {
    constructor(
        private readonly rec: AlbumRecord,
        private readonly records: DerivedRecords,
    ) {}

    get collectionID(): number {
        return this.rec.collectionID;
    }
    get name(): string {
        return this.rec.name;
    }
    get type(): CollectionType {
        return this.rec.type;
    }
    get isShared(): boolean {
        return this.rec.isShared;
    }
    get updationTime(): number {
        return this.rec.updationTime;
    }
    get fileIDs(): number[] {
        return this.rec.fileIDs;
    }

    get photos(): { list: () => Photo[] } {
        return { list: (): Photo[] => this.listPhotos() };
    }

    record(): AlbumRecord {
        return this.rec;
    }

    private listPhotos(): Photo[] {
        const out: Photo[] = [];
        for (const id of this.rec.fileIDs) {
            const p = this.records.photos.get(id);
            if (p) out.push(new Photo(p));
        }
        return out;
    }
}

export interface AlbumsAPI {
    list(): Album[];
    byName(args: { albumName: string }): Album | undefined;
    byID(args: { collectionID: number }): Album | undefined;
}

export interface PhotosAPI {
    byID(args: { fileID: number }): Photo | undefined;
    // Plain records for the requested ids, in the order requested, each id at
    // most once, unknown ids dropped.
    records(args: { fileIDs: number[] }): PhotoRecord[];
}

export type GroupBy = "day" | "week" | "month";

// A filter over the timeline. All fields are optional and combine with AND.
// Hidden photos are never included, regardless of this filter.
export interface PhotoFilter {
    // Keep only photos that belong to this album.
    albumID?: number;
    // Case-insensitive substring of the title, caption, or any album name the
    // photo belongs to.
    text?: string;
    // Keep only photos of one of these types.
    fileTypes?: FileType[];
    // `true` keeps only geotagged photos; `false` keeps only those without a
    // location; omitted places no constraint.
    hasLocation?: boolean;
    // Archived photos are excluded unless this is `true`. Defaults to `false`.
    includeArchived?: boolean;
}

export interface TimelineGroup {
    // The period's identity: `YYYY-MM-DD` for day, `YYYY-Www` (ISO 8601 week,
    // e.g. `2025-W32`) for week, and `YYYY-MM` for month.
    key: string;
    // Local-time milliseconds at the start of the period.
    startsAt: number;
    // The period's files, newest first, each file once.
    fileIDs: number[];
}

export interface TimelineAPI {
    groups(args: { groupBy: GroupBy; filter?: PhotoFilter }): TimelineGroup[];
}

export const makeAlbumsAPI = (derive: () => DerivedRecords): AlbumsAPI => ({
    list: (): Album[] => {
        const records = derive();
        return [...records.albums.values()]
            .sort(byNewestAlbum)
            .map((rec) => new Album(rec, records));
    },
    byID: ({ collectionID }): Album | undefined => {
        const records = derive();
        const rec = records.albums.get(collectionID);
        return rec ? new Album(rec, records) : undefined;
    },
    byName: ({ albumName }): Album | undefined => {
        const records = derive();
        // Names are not unique in Ente; resolve a collision deterministically
        // to the newest-updated album, matching `list` order.
        const match = [...records.albums.values()]
            .sort(byNewestAlbum)
            .find((rec) => rec.name === albumName);
        return match ? new Album(match, records) : undefined;
    },
});

export const makePhotosAPI = (derive: () => DerivedRecords): PhotosAPI => ({
    byID: ({ fileID }): Photo | undefined => {
        const rec = derive().photos.get(fileID);
        return rec ? new Photo(rec) : undefined;
    },
    records: ({ fileIDs }): PhotoRecord[] => {
        const { photos } = derive();
        const seen = new Set<number>();
        const out: PhotoRecord[] = [];
        for (const id of fileIDs) {
            if (seen.has(id)) continue;
            const rec = photos.get(id);
            if (rec) {
                out.push(rec);
                seen.add(id);
            }
        }
        return out;
    },
});

export const makeTimelineAPI = (derive: () => DerivedRecords): TimelineAPI => ({
    groups: ({ groupBy, filter }): TimelineGroup[] => {
        const records = derive();
        return groupPhotos(filterPhotos(records, filter), groupBy);
    },
});

// Apply a `PhotoFilter` to the projection. Hidden photos are always dropped;
// archived photos are dropped unless `includeArchived` asks for them.
const filterPhotos = (
    records: DerivedRecords,
    filter?: PhotoFilter,
): PhotoRecord[] => {
    const f = filter ?? {};
    const includeArchived = f.includeArchived ?? false;
    const needle = f.text?.toLowerCase();
    const out: PhotoRecord[] = [];
    for (const rec of records.photos.values()) {
        if (rec.isHidden) continue;
        if (rec.isArchived && !includeArchived) continue;
        if (f.albumID !== undefined && !rec.albumIDs.includes(f.albumID))
            continue;
        if (f.fileTypes !== undefined && !f.fileTypes.includes(rec.fileType))
            continue;
        if (f.hasLocation !== undefined) {
            const has =
                rec.latitude !== undefined && rec.longitude !== undefined;
            if (has !== f.hasLocation) continue;
        }
        if (needle !== undefined && !matchesText(rec, needle, records))
            continue;
        out.push(rec);
    }
    return out;
};

const matchesText = (
    rec: PhotoRecord,
    needle: string,
    records: DerivedRecords,
): boolean => {
    if (rec.title.toLowerCase().includes(needle)) return true;
    if (rec.caption !== undefined && rec.caption.toLowerCase().includes(needle))
        return true;
    for (const id of rec.albumIDs) {
        const album = records.albums.get(id);
        if (album && album.name.toLowerCase().includes(needle)) return true;
    }
    return false;
};

// Bucket photos into periods, groups newest first, members newest first.
const groupPhotos = (
    photos: PhotoRecord[],
    groupBy: GroupBy,
): TimelineGroup[] => {
    const buckets = new Map<
        string,
        { startsAt: number; recs: PhotoRecord[] }
    >();
    for (const rec of photos) {
        const { key, startsAt } = periodOf(rec.takenAt, groupBy);
        const bucket = buckets.get(key);
        if (bucket) bucket.recs.push(rec);
        else buckets.set(key, { startsAt, recs: [rec] });
    }
    const groups: TimelineGroup[] = [];
    for (const [key, bucket] of buckets) {
        bucket.recs.sort(byNewest);
        groups.push({
            key,
            startsAt: bucket.startsAt,
            fileIDs: bucket.recs.map((r) => r.fileID),
        });
    }
    groups.sort((a, b) => b.startsAt - a.startsAt);
    return groups;
};

const pad = (n: number): string => String(n).padStart(2, "0");

const dateKey = (d: Date): string =>
    `${d.getFullYear()}-${pad(d.getMonth() + 1)}-${pad(d.getDate())}`;

const WEEK_MS = 7 * 24 * 60 * 60 * 1000;

// The ISO 8601 week key `YYYY-Www` for the week starting at the given Monday.
// The week-year is the year of that week's Thursday, so it can differ from the
// calendar year at the January/December boundary (e.g. 2024-12-30 is 2025-W01).
const isoWeekKey = (monday: Date): string => {
    const thursday = new Date(
        monday.getFullYear(),
        monday.getMonth(),
        monday.getDate() + 3,
    );
    const isoYear = thursday.getFullYear();
    // Thursday of ISO week 1 is the Thursday of the week containing January 4.
    const jan4 = new Date(isoYear, 0, 4);
    const week1Thursday = new Date(
        isoYear,
        0,
        4 + 3 - ((jan4.getDay() + 6) % 7),
    );
    const week =
        1 +
        Math.round((thursday.getTime() - week1Thursday.getTime()) / WEEK_MS);
    return `${isoYear}-W${pad(week)}`;
};

// The period a millisecond instant falls in, in local time. Weeks start on
// Monday. `Date` normalizes out-of-range day arguments, so the week's Monday
// is correct across month and year boundaries.
const periodOf = (
    takenAt: number,
    groupBy: GroupBy,
): { key: string; startsAt: number } => {
    const d = new Date(takenAt);
    const year = d.getFullYear();
    const month = d.getMonth();
    const day = d.getDate();

    if (groupBy === "month") {
        const start = new Date(year, month, 1);
        return { key: `${year}-${pad(month + 1)}`, startsAt: start.getTime() };
    }
    if (groupBy === "week") {
        // getDay(): 0=Sunday..6=Saturday; shift so Monday is the week start.
        const fromMonday = (d.getDay() + 6) % 7;
        const start = new Date(year, month, day - fromMonday);
        return { key: isoWeekKey(start), startsAt: start.getTime() };
    }
    const start = new Date(year, month, day);
    return { key: dateKey(start), startsAt: start.getTime() };
};