mgtzm/src/Item.zig

const std = @import("std");

const json = @import("json.zig");
const Db = @import("Db.zig");
const sqlite = @import("sqlite");

const Self = @This();

pub const Tag = struct {
    // :0 for C compatility
    name: [:0]const u8,
    value: ?[:0]const u8,
};

id: ?i64, // If null, the object hasn't been persisted
tags: ?[]Tag,
allocator: ?std.mem.Allocator = null,

pub fn deinit(self: *Self) void {
    // If there's no allocator there has been no allocations
    const allocator = self.allocator orelse return;
    const tags = self.tags orelse return;

    // Free each tag
    for (tags) |*tag| {
        allocator.free(tag.name);

        if (tag.value) |value| {
            allocator.free(value);
        }
    }

    // Free the tags buffer
    allocator.free(tags);
}

pub fn persist(self: *Self, db: *sqlite.Db) !void {
    // Insert only if there's no ID.
    if (self.id == null) {
        const query = "INSERT INTO item VALUES(NULL);";
        try db.exec(query, .{}, .{});

        // Update the ID field
        self.id = try Db.getLastId(db);
    }

    // If the tags haven't been initialized, don't touch anything
    if (self.tags) |tags| {
        // Create new tags if they don't exist
        // TODO: Do the "if they don't exist" part.
        for (tags) |*tags_i| {
            const name_query = "INSERT INTO tag (name) VALUES (?)";
            try db.exec(name_query, .{}, .{ .name = tags_i.name });
            const rel_query = "INSERT INTO item_tag (item, tag, value) VALUES (?, ?, ?);";
            try db.exec(rel_query, .{}, .{ .item = self.id, .tag = tags_i.name, .value = tags_i.value });
        }
    }
}

pub fn getTagsById(id: i64, db: *sqlite.Db, allocator: std.mem.Allocator) !?[]Tag {
    var stmt = try db.prepare("SELECT tag, value FROM item_tag WHERE item = ?");
    defer stmt.deinit();

    const res = try stmt.all(Tag, allocator, .{}, .{ .id = id });

    if (res.len < 1) {
        // Detect wether it returns 0 because it has no tags or because it doesn't exist
        const exists = (try db.one(i64, "SELECT COUNT(id) FROM item WHERE id = ?", .{}, .{id})).?;
        return if (exists == 0) null else res;
    }

    return res;
}

/// Convert into a JSON object. A call to deinit() is necessary from the caller's side
pub fn toJson(self: Self) json.Obj {
    // Main object
    var jobj = json.Obj.newObject();

    // Add id (i64|null)
    jobj.objectAdd("id", if (self.id) |id| &json.Obj.newInt64(id) else null);

    // Add tags only if they're initialized
    if (self.tags) |tags| {
        var jtags = json.Obj.newObject();
        jobj.objectAdd("tags", &jtags);

        for (tags) |tag_i| {
            const jtag = if (tag_i.value) |value|
                &json.Obj.newString(value)
            else
                null;

            jtags.objectAdd(tag_i.name, jtag);
        }
    } else {
        // If nothing is found, set it to null
        // just to make it more explicit
        jobj.objectAdd("tags", null);
    }

    return jobj;
}

pub fn fromJson(jobj: json.Obj, allocator: std.mem.Allocator) !Self {
    // Try to assemble a Item object from a JSON string
    // An item could be just an id, just tags or both.

    var tags: ?[]Tag = null;

    if (jobj.objectGet("tags") catch null) |*jtags| {
        defer jtags.deinit();

        // Reserve space for slice of tags
        const len = @intCast(usize, jtags.objectLen());
        tags = try allocator.alloc(Tag, len);

        var iter = jtags.objectGetIterator();

        var i: usize = 0;
        while (iter.next()) |*tag| {
            // Whe know it's not null at this point
            tags.?[i].name = try allocator.dupeZ(u8, tag.key);
            tags.?[i].value = if (tag.value) |*value| try allocator.dupeZ(u8, value.getString()) else null;

            i += 1;
        }
    }

    var id: ?i64 = null;

    if (jobj.objectGet("id") catch null) |*jid| {
        defer jid.deinit();

        id = jid.getInt64();
    }

    // TODO: What should be done when both things are null?
    //       Return a null Obj or leave it as-is?

    return Self{
        .id = id,
        .tags = tags,
        .allocator = allocator,
    };
}