local mongo = require 'mongo'
local client = mongo.Client('mongodb://127.0.0.1')
local collection = client:getCollection('lua-mongo-test', 'test')
collection:drop() -- Clear collection

-- Common variables
local id = mongo.ObjectID()
local query1 = mongo.BSON('{ "age" : { "$gt" : 25 } }')
local query2 = mongo.BSON{_id = id}

-- Implicit Lua/JSON to BSON conversion where BSON is required
collection:insert{_id = id, name = 'John Smith', age = 50}
collection:insert('{ "name" : "Bobby", "age" : 3 }')

-- Iterate documents in a for-loop
for person in collection:find({}, {sort = {age = -1}}):iterator() do
    print(person.name, person.age)
end

-- Fetch single document
local person = collection:findOne(query1):value()
print(person.name, person.age)

-- Access to BSON where needed
local bson = collection:findOne(query1)
print(bson) -- BSON is converted to JSON using tostring()

-- Explicit BSON to Lua conversion
local person = bson:value()
print(person.name, person.age)

-- Transparently include BSON documents in other documents
collection:update(query2, {age = 60, old = bson}) -- Update document
collection:remove(query2) -- Remove document

local bulk = collection:createBulkOperation()

-- Multiple insertions
bulk:insert{a = 1}
bulk:insert{b = 2}
bulk:insert{c = 3}

-- Multiple modifications
bulk:replaceOne({a = 1}, {b = 1})
bulk:updateMany('{}', '{ "$inc" : { "b" : 2 } }')
bulk:removeOne{c = 3}

-- Execute queued operations
bulk:execute()

local TestClass = {} -- Class metatable

local function TestObject(id, name) -- Constructor
    local object = {
        id = id,
        name = name,
    }
    return setmetatable(object, TestClass)
end

function TestClass:__tostring() -- Method
    return tostring(self.id) .. ' --> ' .. self.name
end

function TestClass:__toBSON() -- Called when object is serialized into BSON
    return {
        _id = self.id,
        binary = mongo.Binary(self.name), -- Store 'name' as BSON Binary for example
    }
end

-- A root '__toBSON' metamethod may return a table or BSON document.
-- A nested '__toBSON' metamethod may return a value, BSON type or BSON document.

-- BSON handler
local function handler(document)
    local id = document._id
    local name = document.binary:unpack() -- Restore 'name' from BSON Binary
    return TestObject(id, name)
end

-- Note that the same handler is called for each document. Thus, the handler should be able
-- to differentiate documents based on some internal criteria.

local object = TestObject(id, 'abc')
print(object)

-- Explicit BSON <-> Lua conversion
local bson = mongo.BSON(object)
local object = bson:value(handler)
print(object)

-- Store object
collection:insert(object)

-- Restore object
local object = collection:findOne(query2):value(handler)
print(object)

-- Iterate objects in a for-loop
for object in collection:find(query2):iterator(handler) do
    print(object)
end