local core = require('openmw.core')
local util = require('openmw.util')

local M = {}

local globalTestsOrder = {}
local globalTests = {}
local globalTestRunner = nil

local localTests = {}
local localTestRunner = nil
local currentLocalTest = nil
local currentLocalTestError = nil

function M.makeUpdateGlobal()
    local fn = function()
        for i, test in ipairs(globalTestsOrder) do
            local name, fn = unpack(test)
            print('TEST_START', i, name)
            local status, err = pcall(fn)
            if status then
                print('TEST_OK', i, name)
            else
                print('TEST_FAILED', i, name, err)
            end
        end
        core.quit()
    end
    local co = coroutine.create(fn)
    return function()
        if coroutine.status(co) ~= 'dead' then
            coroutine.resume(co)
        end
    end
end

function M.registerGlobalTest(name, fn)
    globalTests[name] = fn
    table.insert(globalTestsOrder, {name, fn})
end

function M.runLocalTest(obj, name)
    currentLocalTest = name
    currentLocalTestError = nil
    obj:sendEvent('runLocalTest', name)
    while currentLocalTest do
        coroutine.yield()
    end
    if currentLocalTestError then
        error(currentLocalTestError, 2)
    end
end

function M.registerLocalTest(name, fn)
    localTests[name] = fn
end

function M.updateLocal()
    if localTestRunner and coroutine.status(localTestRunner) ~= 'dead' then
        if not core.isWorldPaused() then
            coroutine.resume(localTestRunner)
        end
    else
        localTestRunner = nil
    end
end

function M.expect(cond, msg)
    if not cond then
        error(msg or '"true" expected', 2)
    end
end

function M.expectEqualWithDelta(v1, v2, delta, msg)
    if math.abs(v1 - v2) > delta then
        error(string.format('%s: %f ~= %f', msg or '', v1, v2), 2)
    end
end

function M.expectAlmostEqual(v1, v2, msg)
    if math.abs(v1 - v2) / (math.abs(v1) + math.abs(v2)) > 0.05 then
        error(string.format('%s: %f ~= %f', msg or '', v1, v2), 2)
    end
end

function M.expectGreaterOrEqual(v1, v2, msg)
    if not (v1 >= v2) then
        error(string.format('%s: %f >= %f', msg or '', v1, v2), 2)
    end
end

function M.expectGreaterThan(v1, v2, msg)
    if not (v1 > v2) then
        error(string.format('%s: %s > %s', msg or '', v1, v2), 2)
    end
end

function M.expectLessOrEqual(v1, v2, msg)
    if not (v1 <= v2) then
        error(string.format('%s: %s <= %s', msg or '', v1, v2), 2)
    end
end

function M.expectEqual(v1, v2, msg)
    if not (v1 == v2) then
        error(string.format('%s: %s ~= %s', msg or '', v1, v2), 2)
    end
end

function M.expectNotEqual(v1, v2, msg)
    if v1 == v2 then
        error(string.format('%s: %s == %s', msg or '', v1, v2), 2)
    end
end

function M.closeToVector(expected, maxDistance)
    return function(actual)
        local distance = (expected - actual):length()
        if distance <= maxDistance then
            return ''
        end
        return string.format('%s is too far from expected %s: %s > %s', actual, expected, distance, maxDistance)
    end
end

---
-- Matcher verifying that given value is an array each element of which matches elements of expected.
-- @function elementsAreArray
-- @param expected#array of values or matcher functions.
-- @usage
-- local t = {42, 13}
-- local matcher = function(actual)
--     if actual ~= 42 then
--         return string.format('%s is not 42', actual)
--     end
--     return ''
-- end
-- expectThat({42, 13}, elementsAreArray({matcher, 13}))
function M.elementsAreArray(expected)
    local expected_matchers = {}
    for i, v in ipairs(expected) do
        if type(v) == 'function' then
            expected_matchers[i] = v
        else
            expected_matchers[i] = function (other)
                if expected[i].__eq(expected[i], other) then
                    return ''
                end
                return string.format('%s element %s does no match expected: %s', i, other, expected[i])
            end
        end
    end
    return function(actual)
        if #actual < #expected_matchers then
            return string.format('number of elements is less than expected: %s < %s', #actual, #expected_matchers)
        end
        local message = ''
        for i, v in ipairs(actual) do
            if i > #expected_matchers then
                message = string.format('%s\n%s element is out of expected range: %s', message, i, #expected_matchers)
                break
            end
            local match_message = expected_matchers[i](v)
            if match_message ~= '' then
                message = string.format('%s\n%s', message, match_message)
            end
        end
        return message
    end
end

---
-- Matcher verifying that given number is not a nan.
-- @function isNotNan
-- @usage
-- expectThat(value, isNotNan())
function M.isNotNan(expected)
    return function(actual)
        if actual ~= actual then
            return 'actual value is nan, expected to be not nan'
        end
        return ''
    end
end

---
-- Verifies that given value matches provided matcher.
-- @function expectThat
-- @param value#any any value to match.
-- @param matcher#function a function returing empty string in the case of success or a message explaining the mismatch.
-- @param msg#string a message to prefix failure reason.
-- @usage
-- local matcher = function(actual)
--     if actual == 42 then
--         return ''
--     end
--     return string.format('%s is not 42', actual)
-- end
-- expectThat(42, matcher)
function M.expectThat(value, matcher, msg)
    local message = matcher(value)
    if message ~= '' then
        error(string.format('%s: actual does not match expected: %s', msg or 'Failure', message), 2)
    end
end

function M.formatActualExpected(actual, expected)
    return string.format('actual: %s, expected: %s', actual, expected)
end

M.eventHandlers = {
    runLocalTest = function(name)  -- used only in local scripts
        fn = localTests[name]
        if not fn then
            core.sendGlobalEvent('localTestFinished', {name=name, errMsg='Local test is not found'})
            return
        end
        localTestRunner = coroutine.create(function()
            local status, err = pcall(fn)
            if status then
                err = nil
            end
            core.sendGlobalEvent('localTestFinished', {name=name, errMsg=err})
        end)
    end,
    localTestFinished = function(data)  -- used only in global scripts
        if data.name ~= currentLocalTest then
            error(string.format('localTestFinished with incorrect name %s, expected %s', data.name, currentLocalTest))
        end
        currentLocalTest = nil
        currentLocalTestError = data.errMsg
    end,
}

return M