test_that("yearmonth constructor and coercion to date works", {
    dates <- seq.Date(from = as.Date("1970-01-01"), length.out = 4, by = "month")
    storage.mode(dates) <- "double" # needed for R <= 4.1.3
    ym4 <- new_yearmonth(0:3)

    expect_identical(as.Date(ym4), dates)

    # formatting --------------------------------------------------------------
    expect_identical(format(ym4), format(as.Date(ym4), "%Y-%b"))
    expect_identical(format(new_yearmonth()), character())

    dat <- as.Date("1900-01-01") + seq.int(from = 0L, to = 200L * 365, by = 180L)
    expected <- as_yearmonth(dat)
    tmp <- as.character(dat)
    years <- as.integer(substr(tmp, 1L, 4L))
    months <- as.integer(substr(tmp, 6L, 7L))
    expect_identical(yearmonth(years, months), expected)
})

test_that("yearmonth, pre-epoch dates work", {
    dates <- seq.Date(from = as.Date("1900-01-01"), length.out = 4, by = "month")
    storage.mode(dates) <- "double" # needed for R <= 4.1.3
    dates2 <- seq.Date(from = as.Date("1899-09-01"), length.out = 4, by = "month")
    storage.mode(dates2) <- "double" # needed for R <= 4.1.3
    expect_identical(as.Date(as_yearmonth(dates)), dates)
    expect_identical(as.Date(as_yearmonth(dates) - 4), dates2)
})

test_that("yearmonth, POSIXlt coercion works", {
    nz <- as.POSIXlt("2021-01-04 02:00:00", tz = "NZ")
    utc <- as.POSIXlt("2021-01-01 00:00:00", tz = "UTC")
    result <- as.POSIXlt(as_yearmonth(nz))

    expect_identical(result, utc)

    dat <- "2021-01-01"
    pos <- as.POSIXlt("2021-01-04", tz = "UTC")
    res1 <- as_yearmonth(pos)

    expect_identical(as.Date(res1), as.Date(dat))

    dat <- "2021-01-01"
    res <- as.POSIXlt(as_yearmonth(dat))
    expect_s3_class(res, "POSIXlt")
    expect_identical(julian(res), julian(as.POSIXlt(dat, tz = "UTC")))
    expect_error(
        as.POSIXlt(as_yearmonth(dat), tz = "GMT"),
        "<grates_yearmonth> objects can only be converted to UTC. If other timezones are required, first convert to <Date> and then proceed as desired.",
        fixed = TRUE
    )
})

test_that("yearmonth, POSIXct coercion works", {
    nz <- as.POSIXct(as.POSIXlt("2021-01-04", tz = "NZ"))
    dat <- as_yearmonth(nz)
    result <- as.POSIXct(dat)
    expect_identical(result, as.POSIXct(as.POSIXlt("2021-01-01", tz = "UTC")))

    pos <- as.POSIXct(as.POSIXlt("2021-01-04", tz = "UTC"))
    res1 <- as_yearmonth(pos)
    expect_identical(as.Date(res1), as.Date("2021-01-01"))

    dat <- "2021-01-01"
    res <- as.POSIXct(as_yearmonth(dat))
    expect_identical(res, as.POSIXct(as.POSIXlt(dat), tz = "UTC"))
    expect_error(
        as.POSIXct(as_yearmonth(dat), tz = "GMT"),
        "<grates_yearmonth> objects can only be converted to UTC. If other timezones are required, first convert to <Date> and then proceed as desired.",
        fixed = TRUE
    )
})

test_that("yearmonth, character coercion works", {
    dat <- "2021-01-04"
    res <- as_yearmonth(dat)
    expect_identical(as.Date(res), as.Date("2021-01-01"))

    dat <- as.factor("2021-01-04")
    res <- as_yearmonth(dat)
    expect_identical(as.Date(res), as.Date("2021-01-01"))

    dat <- "2020-12-28"
    res <- as.character(as_yearmonth(dat))
    expect_identical(res, as.character(format(as.Date(dat), format = "%Y-%b")))
})

test_that("as_yearmonth, misc errors and warnings", {
    expect_error(
        as_yearmonth(TRUE),
        "Not implemented for class [logical].",
        fixed = TRUE
    )
    expect_error(as_yearmonth("bob"))
})


test_that("yearmonth, as.list works", {
    dat <- as_yearmonth(c("2020-12-28", "2021-01-04"))
    res <- list(as_yearmonth("2020-12-28"), as_yearmonth("2021-01-04"))
    expect_identical(res, as.list(dat))
})

test_that("yearmonth, accessors", {
    dat <- as_yearmonth(as.Date("2020-12-28"))
    expect_identical(get_year(dat), 2020L)
})

test_that("yearmonth, is_yearmonth works", {
    dat <- as_yearmonth(Sys.Date())
    expect_true(is_yearmonth(dat))
    expect_false(is_yearmonth("bob"))
})

test_that("yearmonth, subsetting works", {
    x <- as.Date("2023-02-15")
    dat <- as_yearmonth(x) + 0:1
    dat <- setNames(dat, c("a", "b"))
    expect_identical(dat[1], c(a=as_yearmonth(x)))
    expect_identical(dat[[2]], as_yearmonth(x + 33))
    dat[1] <- as_yearmonth(x+33)
    expect_identical(dat[1], c(a=as_yearmonth(x + 33)))
    dat[[2]] <- dat[[1]]
    expect_identical(dat[[2]], dat[[1]])
    expect_error(
        dat[1] <- "bob",
        "Can only assign <grates_yearmonth> objects in to an <grates_yearmonth> object.",
        fixed = TRUE
    )
})

test_that("yearmonth, combine works", {
    x <- Sys.Date()
    dat <- as_yearmonth(x)
    expect_identical(c(dat, dat), as_yearmonth(c(x, x)))
    expect_error(
        c(dat, "bob"),
        "Unable to combine <grates_yearmonth> objects with other classes.",
        fixed = TRUE
    )
})

test_that("yearmonth operators and math work", {
    # comparison operators ----------------------------------------------------
    x <- Sys.Date()
    dat <- as_yearmonth(x)
    expect_true(dat == dat)
    expect_false(dat != dat)
    expect_true(dat == dat)
    expect_true(dat <= dat + 1)
    expect_true(dat >= dat - 1)
    expect_true(dat < dat + 1)
    expect_true(dat > dat - 1)
    expect_true(dat != dat + 1)
    expect_error(
        dat == TRUE,
        "Can only compare <grates_yearmonth> objects with <grates_yearmonth> objects.",
        fixed = TRUE
    )

    # addition ----------------------------------------------------------------
    x <- as.Date("2021-01-05")
    y <- as.Date("2021-01-04")
    dat1 <- as_yearmonth(x)
    dat2 <- dat1 + 0:1
    expect_identical(as.Date(dat2), as.Date(c("2021-01-01", "2021-02-01")))
    expect_identical(dat2, 0:1 + dat1)
    expect_identical(+dat1, dat1)
    expect_error(
        dat1 + 1.5,
        "Can only add integers to <grates_yearmonth> objects.",
        fixed = TRUE
    )
    expect_error(
        dat1 + dat1,
        "Cannot add <grates_yearmonth> objects to each other.",
        fixed = TRUE
    )

    # subtraction -------------------------------------------------------------
    x <- as.Date("2021-01-05")
    y <- as.Date("2021-01-04")
    dat1 <- as_yearmonth(x)
    dat2 <- dat1 - 0:1
    expect_identical(as.Date(dat2), as.Date(c("2021-01-01", "2020-12-01")))
    expect_identical(as.integer(dat2 - dat1), c(0L, -1L))
    expect_error(
        1 - dat1,
        "Can only subtract from a <grates_yearmonth> object, not vice-versa.",
        fixed = TRUE
    )
    expect_error(
        -dat1,
        "Cannot negate a <grates_yearmonth> object.",
        fixed = TRUE
    )
    expect_error(
        dat1 - 1.5,
        "Can only subtract whole numbers and other <grates_yearmonth> objects from <grates_yearmonth> objects.",
        fixed = TRUE
    )

    # Other operations error
    x <- as_yearmonth(as.Date("2021-01-05"))
    expect_error(dat * 3)
    expect_error(dat / 3)
    expect_error(dat ^ 3)
    expect_error(dat %% 3)
    expect_error(dat %/% 3)
    expect_error(dat & 3)
    expect_error(dat | 3)
    expect_error(!dat)

    # Math
    x <- as_yearmonth(as.Date("2021-01-05"))
    dat <- c(x + 0:1, new_yearmonth(NA_integer_))
    expect_identical(is.nan(dat), c(FALSE, FALSE, FALSE))
    expect_identical(is.finite(dat), c(TRUE, TRUE, FALSE))
    expect_identical(is.infinite(dat), c(FALSE, FALSE, FALSE))
    expect_error(abs(dat))
})

test_that("yearmonth, miscellaneous work", {
    expect_identical(new_yearmonth(-1.5), new_yearmonth(-2L))
    expect_error(new_yearmonth("bob"), "`x` must be integer.", fixed = TRUE)
    expect_error(
        as_yearmonth(NA_character_),
        "Unable to parse any entries of `x` as Dates.",
        fixed = TRUE
    )
    dat <- Sys.Date()
    dat <- c(dat, dat - 45L)
    dat <- as_yearmonth(dat)
    expect_identical(rep(dat, 2L), c(dat, dat))
    expect_identical(rep(dat, each = 2L), c(dat[[1]], dat[[1]], dat[[2]], dat[[2]]))
    expect_identical(unique(c(dat, dat)), dat)
    dat <- as_yearmonth(as.Date("1970-01-01"))
    expect_identical(
        seq(dat, dat + 11, by = 2L),
        new_yearmonth(c(0L, 2L, 4L, 6L, 8L, 10L))
    )
    expect_error(
        seq(dat, dat + 11, by = 2.5),
        "`by` must be an integer of length 1.",
        fixed = TRUE
    )
    expect_error(
        seq(dat, as.integer(dat + 11), by = 2.5),
        "`to` must be a <grates_yearmonth> object of length 1.",
        fixed = TRUE
    )
    expect_identical(as.integer(new_yearmonth(100L)), 100L)
    expect_identical(as.double(new_yearmonth(100L)), 100)
    expect_identical(min(c(dat, dat+11)), dat)
    expect_identical(max(c(dat, dat+11)), dat+11)
    expect_identical(range(seq(dat, dat + 12, by = 2L)), c(dat, dat+12))
    expect_error(
        any(dat),
        "`any()` is not supported for <grates_yearmonth> objects.",
        fixed = TRUE
    )

    expect_identical(yearmonth(1L,1L),yearmonth(1.5,1.5))
    expect_error(yearmonth(1L), "Cannot recycle a vector of length 0:", fixed = TRUE)
    expect_error(yearmonth(1:2,1:3), "Can only recycle vectors of length 1:", fixed = TRUE)
    expect_error(yearmonth(year = character()), "`year` must be integer.", fixed = TRUE)
    expect_error(yearmonth(month = character()), "`month` must be integer.")
    expect_error(yearmonth(1L,0L), "Months must be integer and between 1 and 12 (inclusive) or NA. Entry 1 is not (it equals 0).", fixed = TRUE)
    expect_error(yearmonth(1L,13L), "Months must be integer and between 1 and 12 (inclusive) or NA. Entry 1 is not (it equals 13).", fixed = TRUE)
})

test_that("yearmonth boundary functions work", {
    dates <- as.Date("2020-01-01") + 0:365
    months <- as_yearmonth(dates)
    starts <- as.Date(months)
    ends <- lapply(starts, function(x) seq(x, by = "1 month", length.out = 2L)[2L])
    ends <- do.call(c, ends) - 1L
    expect_identical(date_start(months), starts)
    expect_identical(date_end(months), ends)
})