-- the tdc function calculates diffs, and returns those
-- diffs as a human-readable string.
local tdc = table.diffcompare

-- the tda function calculates diffs, applies the diffs to the second
-- table, and then returns true if the second table equals the first.
local tda = table.diffapply

function unittests.diffcompare()
    local mtab = nil
    local rtab = nil

    -- No differences in these simple-valued tables.
    assert(tdc({}, {a=true}, {}, {a=true}) == "")
    assert(tdc({}, {a=5}, {}, {a=5}) == "");
    assert(tdc({}, {a="foo"}, {}, {a="foo"}) == "")

    -- Test transmission of missing simple values.
    assert(tdc({}, {a=true}, {}, {}) == "a=true;")
    assert(tdc({}, {a=5}, {}, {}) == "a=5;");
    assert(tdc({}, {a="foo"}, {}, {}) == "a=foo;")

    -- Test the replacement of simple values.
    assert(tdc({}, {a=true}, {}, {a=false}) == "a=true;")
    assert(tdc({}, {a=5}, {}, {a=4}) == "a=5;");
    assert(tdc({}, {a="foo"}, {}, {a="bar"}) == "a=foo;")

    -- Test the clearing of values.
    assert(tdc({}, {}, {}, {a=true}) == "a=nil;")
    assert(tdc({}, {}, {}, {a=5}) == "a=nil;");
    assert(tdc({}, {}, {}, {a="foo"}) == "a=nil;")

    -- Try boolean keys.
    assert(tdc({}, {[true]=3}, {}, {}) == "true=3;")
    assert(tdc({}, {}, {}, {[true]=3}) == "true=nil;")

    -- Try number keys.
    assert(tdc({}, {[7]=3}, {}, {}) == "7=3;")
    assert(tdc({}, {}, {}, {[7]=3}) == "7=nil;")

    -- Try a table with multiple keys.
    assert(tdc({}, {a=4, b=5, c=6}, {}, {b=5, c=7, d=8}) == "a=4;c=6;d=nil;")

    -- Nonsortable keys should be ignored (no diffs).
    assert(tdc({}, {[{}]=3}, {}, {}) == "")

    -- Try a table containing a class.
    assert(tdc({}, {a=deque}, {}, {}) == "a=class deque;")

    -- Try a table containing a pointer to the global environment.
    assert(tdc({}, {a=_G}, {}, {}) == "a=globals;")

    -- GlobalDB tables should be forced to NIL.
    assert(tdc({}, {a=global("foo")}, {}, {a=global("foo")}) == "a=nil;");
    assert(tdc({}, {}, {}, {a=global("foo")}) == "a=nil;");
    assert(tdc({}, {a=global("foo")}, {}, {}) == "");
    
    -- Set up some numbered tables for tests involving such.
    local mtab10 = {}
    local stab10 = {}
    local mtnmap = {}
    local stnmap = {}
    mtnmap[mtab10] = 10
    stnmap[stab10] = 10

    -- confirm that numbered tables are being transmitted.
    assert(tdc(mtnmap, {a=mtab10}, stnmap, {}) == "a=table 10;")
    assert(tdc(mtnmap, {a=mtab10}, stnmap, {a=stab10}) == "")
    assert(tdc(mtnmap, {a=3}, stnmap, {a=stab10}) == "a=3;")
    assert(tdc(mtnmap, {}, stnmap, {a=stab10}) == "a=nil;")

    -- confirm that unnumbered tables are forced to nil.
    assert(tdc(mtnmap, {a={}}, stnmap, {}) == "")
    assert(tdc(mtnmap, {a={}}, stnmap, {a=3}) == "a=nil;")

    -- transmit a correction to the metatable.
    mtab={}
    stab={}
    setmetatable(mtab, mtab10)
    setmetatable(stab, stab10)
    assert(tdc(mtnmap, mtab, stnmap, {}) == "nil=table 10;")
    assert(tdc(mtnmap, mtab, stnmap, stab) == "")
    assert(tdc(mtnmap, {}, stnmap, stab) == "nil=nil;")

    -- we're not going to test tangibles
    -- creating tangibles here is too difficult.
end

function unittests.diffapply()
    local tab10={id=tab10}
    local tab11={id=tab11}
    local tnmap={}
    tnmap[tab10] = 10
    tnmap[tab11] = 11
    local mtab=nil
    local stab=nil

    -- verify some simple values.
    assert(tda(tnmap, {a=1}, {}))
    assert(tda(tnmap, {[true]="foo"}, {}))
    assert(tda(tnmap, {[3]=false}, {}))

    -- verify a table with multiple simple values.
    assert(tda(tnmap, {a=1, b=2, c=3}, {}))

    -- verify that it can remove or replace wrong values.
    assert(tda(tnmap, {a=1,b=2}, {b=3,c=4}))

    -- verify a table containing another table.
    assert(tda(tnmap, {a=tab10, b=tab11}, {}))

    -- verify a table containing a class.
    assert(tda(tnmap, {a=deque, b=table}, {}))

    -- verify a table containing the global environment.
    assert(tda(tnmap, {a=_G}, {}))

    -- GlobalDB tables should be forced to NIL.
    rtab={a=3}
    assert(not tda({}, {a=global("foo")}, rtab))
    assert(rtab.a == nil)

    -- Unnumbered tables should be forced to NIL.
    rtab={a=3}
    assert(not tda({}, {a={}}, rtab))
    assert(rtab.a == nil)

    -- transmit a correction to the metatable
    mtab={}
    rtab={}
    setmetatable(mtab, tab10)
    assert(tda(tnmap, mtab, rtab))
    assert(getmetatable(rtab) == tab10)

    -- transmit a clearing of the metatable
    mtab={}
    rtab={}
    setmetatable(rtab, tab10)
    assert(tda(tnmap, mtab, rtab))
    assert(getmetatable(rtab) == nil)

    -- don't test tangibles.
end