fediglam/src/api/services/communities.zig

const std = @import("std");
const builtin = @import("builtin");
const util = @import("util");
const sql = @import("sql");

const Uuid = util.Uuid;
const DateTime = util.DateTime;

pub const Community = struct {
    pub const Kind = enum {
        admin,
        local,

        pub const jsonStringify = util.jsonSerializeEnumAsString;
    };

    pub const Scheme = enum {
        https,
        http,

        pub const jsonStringify = util.jsonSerializeEnumAsString;
    };
    id: Uuid,

    owner_id: ?Uuid,
    host: []const u8,
    name: []const u8,

    scheme: Scheme,
    kind: Kind,
    created_at: DateTime,
};

pub const CreateOptions = struct {
    name: ?[]const u8 = null,
    kind: Community.Kind = .local,
};

pub const CreateError = error{
    DatabaseFailure,
    UnsupportedScheme,
    InvalidOrigin,
    CommunityExists,
};

pub fn create(db: anytype, origin: []const u8, options: CreateOptions, alloc: std.mem.Allocator) CreateError!Uuid {
    const scheme_len = std.mem.indexOfScalar(u8, origin, ':') orelse return error.InvalidOrigin;
    const scheme_str = origin[0..scheme_len];
    const scheme = std.meta.stringToEnum(Community.Scheme, scheme_str) orelse return error.UnsupportedScheme;

    // host must be in the format "{scheme}://{host}"
    if (origin.len <= scheme_len + ("://").len or
        origin[scheme_len] != ':' or
        origin[scheme_len + 1] != '/' or
        origin[scheme_len + 2] != '/') return error.InvalidOrigin;

    const host = origin[scheme_len + 3 ..];

    // community cannot use non-default ports (except for testing)
    // NOTE: Do not add, say localhost and localhost:80 or bugs may happen.
    // Avoid using non-default ports unless a test can't be conducted without it.
    if (std.mem.indexOfScalar(u8, host, ':') != null and builtin.mode != .Debug) return error.InvalidOrigin;

    // community cannot be hosted on a path
    if (std.mem.indexOfScalar(u8, host, '/') != null) return error.InvalidOrigin;

    // Require TLS on production builds
    if (scheme != .https and builtin.mode != .Debug) return error.UnsupportedScheme;

    const id = Uuid.randV4(util.getThreadPrng());

    // TODO: wrap this in TX
    if (db.queryRow(
        std.meta.Tuple(&.{Uuid}),
        "SELECT id FROM community WHERE host = $1",
        .{host},
        alloc,
    )) |_| {
        return error.CommunityExists;
    } else |err| switch (err) {
        error.NoRows => {},
        else => return error.DatabaseFailure,
    }

    db.insert("community", .{
        .id = id,
        .owner_id = null,
        .host = host,
        .name = options.name orelse host,
        .scheme = scheme,
        .kind = options.kind,
        .created_at = DateTime.now(),
    }, alloc) catch return error.DatabaseFailure;

    return id;
}

pub const GetError = error{
    NotFound,
    DatabaseFailure,
};

fn getWhere(
    db: anytype,
    comptime where: []const u8,
    args: anytype,
    alloc: std.mem.Allocator,
) GetError!Community {
    return db.queryRow(
        Community,
        std.fmt.comptimePrint(
            \\SELECT {s}
            \\FROM community
            \\WHERE {s}
            \\LIMIT 1
        ,
            .{
                comptime util.comptimeJoin(",", std.meta.fieldNames(Community)),
                where,
            },
        ),
        args,
        alloc,
    ) catch |err| switch (err) {
        error.NoRows => error.NotFound,
        else => error.DatabaseFailure,
    };
}

pub fn get(db: anytype, id: Uuid, alloc: std.mem.Allocator) GetError!Community {
    return getWhere(db, "id = $1", .{id}, alloc);
}

pub fn getByHost(db: anytype, host: []const u8, alloc: std.mem.Allocator) GetError!Community {
    return getWhere(db, "host = $1", .{host}, alloc);
}

pub fn transferOwnership(db: anytype, community_id: Uuid, new_owner: Uuid) !void {
    // TODO: check that this actually found/updated the row (needs update to sql lib)
    db.exec(
        "UPDATE community SET owner_id = $1 WHERE id = $2",
        .{ new_owner, community_id },
        null,
    ) catch return error.DatabaseFailure;
}

pub const QueryArgs = struct {
    pub const OrderBy = enum {
        name,
        host,
        created_at,

        pub const jsonStringify = util.jsonSerializeEnumAsString;
    };

    pub const Direction = enum {
        ascending,
        descending,

        pub const jsonStringify = util.jsonSerializeEnumAsString;
    };

    pub const PageDirection = enum {
        forward,
        backward,

        pub const jsonStringify = util.jsonSerializeEnumAsString;
    };

    pub const Prev = std.meta.Child(std.meta.fieldInfo(QueryArgs, .prev).field_type);
    pub const OrderVal = std.meta.fieldInfo(Prev, .order_val).field_type;

    // Max items to fetch
    max_items: usize = 20,

    // Selection filters
    owner_id: ?Uuid = null, // searches for communities owned by this user
    like: ?[]const u8 = null, // searches for communities with host or name LIKE '%?%'
    created_before: ?DateTime = null,
    created_after: ?DateTime = null,

    // Ordering parameter
    order_by: OrderBy = .created_at,
    direction: Direction = .ascending,

    // Page start parameter
    // This struct is a reference to the last value scanned
    // If prev is present, then prev.order_val must have the same tag as order_by
    // "prev" here refers to it being the previous value returned. It may be that
    // prev refers to the item directly after the results you are about to recieve,
    // if you are querying the previous page.
    prev: ?struct {
        id: Uuid,
        order_val: union(OrderBy) {
            name: []const u8,
            host: []const u8,
            created_at: DateTime,
        },
    } = null,

    // What direction to scan the page window
    // If "forward", then "prev" is interpreted as the item directly before the items
    // to query, in the direction of "direction" above. If "backward", then the opposite
    page_direction: PageDirection = .forward,
};

pub const QueryResult = struct {
    items: []const Community,

    prev_page: QueryArgs,
    next_page: QueryArgs,
};

const QueryBuilder = struct {
    array: std.ArrayList(u8),
    where_clauses_appended: usize = 0,

    pub fn init(alloc: std.mem.Allocator) QueryBuilder {
        return QueryBuilder{ .array = std.ArrayList(u8).init(alloc) };
    }

    pub fn deinit(self: *const QueryBuilder) void {
        self.array.deinit();
    }

    pub fn andWhere(self: *QueryBuilder, clause: []const u8) !void {
        if (self.where_clauses_appended == 0) {
            try self.array.appendSlice("WHERE ");
        } else {
            try self.array.appendSlice(" AND ");
        }

        try self.array.appendSlice(clause);
        self.where_clauses_appended += 1;
    }
};

const max_max_items = 100;

pub const QueryError = error{
    PageArgMismatch,
    DatabaseError,
};

// Retrieves up to `args.max_items` Community entries matching the given query
// arguments.
// `args.max_items` is only a request, and fewer entries may be returned.
pub fn query(db: anytype, args: QueryArgs, alloc: std.mem.Allocator) !QueryResult {
    var builder = QueryBuilder.init(alloc);
    defer builder.deinit();

    try builder.array.appendSlice(
        std.fmt.comptimePrint(
            \\SELECT {s}
            \\FROM community
            \\
        , .{comptime util.comptimeJoin(",", std.meta.fieldNames(Community))}),
    );

    const max_items = if (args.max_items > max_max_items) max_max_items else args.max_items;

    if (args.owner_id != null) try builder.andWhere("owner_id = $1");
    if (args.like != null) try builder.andWhere("(host LIKE ('%' || $2 || '%') OR name LIKE ('%' || $2 || '%'))");
    if (args.created_before != null) try builder.andWhere("created_at < $3");
    if (args.created_after != null) try builder.andWhere("created_at > $4");
    if (args.prev) |prev| {
        if (prev.order_val != args.order_by) return error.PageArgMismatch;

        try builder.andWhere(switch (args.order_by) {
            .name => "(name, id)",
            .host => "(host, id)",
            .created_at => "(created_at, id)",
        });
        _ = try builder.array.appendSlice(switch (args.direction) {
            .ascending => switch (args.page_direction) {
                .forward => " > ",
                .backward => " < ",
            },
            .descending => switch (args.page_direction) {
                .forward => " < ",
                .backward => " > ",
            },
        });

        _ = try builder.array.appendSlice("($5, $6)");
    }

    const direction_string = switch (args.direction) {
        .ascending => " ASC ",
        .descending => " DESC ",
    };
    _ = try builder.array.appendSlice("\nORDER BY ");
    _ = try builder.array.appendSlice(@tagName(args.order_by));
    _ = try builder.array.appendSlice(direction_string);
    _ = try builder.array.appendSlice(", id ");
    _ = try builder.array.appendSlice(direction_string);

    _ = try builder.array.appendSlice("\nLIMIT $7");

    const query_args = .{
        args.owner_id,
        args.like,
        args.created_before,
        args.created_after,
        if (args.prev) |prev| prev.order_val else null,
        if (args.prev) |prev| prev.id else null,
        max_items,
    };

    try builder.array.append(0);

    var results = try db.queryWithOptions(
        Community,
        std.meta.assumeSentinel(builder.array.items, 0),
        query_args,
        .{ .prep_allocator = alloc, .ignore_unused_arguments = true },
    );
    defer results.finish();

    const result_buf = try alloc.alloc(Community, args.max_items);
    errdefer alloc.free(result_buf);

    var count: usize = 0;
    errdefer for (result_buf[0..count]) |c| util.deepFree(alloc, c);

    for (result_buf) |*c| {
        c.* = (try results.row(alloc)) orelse break;

        count += 1;
    }

    var next_page = args;
    var prev_page = args;
    prev_page.page_direction = .backward;
    next_page.page_direction = .forward;
    if (count != 0) {
        prev_page.prev = .{
            .id = result_buf[0].id,
            .order_val = getOrderVal(result_buf[0], args.order_by),
        };

        next_page.prev = .{
            .id = result_buf[count - 1].id,
            .order_val = getOrderVal(result_buf[count - 1], args.order_by),
        };
    }
    // TODO: This will give incorrect links on an empty page

    return QueryResult{
        .items = result_buf[0..count],

        .next_page = next_page,
        .prev_page = prev_page,
    };
}

fn getOrderVal(community: Community, order_val: QueryArgs.OrderBy) QueryArgs.OrderVal {
    return switch (order_val) {
        .name => .{ .name = community.name },
        .host => .{ .host = community.host },
        .created_at => .{ .created_at = community.created_at },
    };
}

pub fn adminCommunityId(db: anytype) !Uuid {
    const row = db.queryRow(
        std.meta.Tuple(&.{Uuid}),
        "SELECT id FROM community WHERE kind = 'admin' LIMIT 1",
        {},
        null,
    ) catch |err| return switch (err) {
        error.NoRows => error.NotFound,
        else => error.DatabaseFailure,
    };

    return row[0];
}