test_that("Simple signature works", {
    skip_on_cran()
    client <- language_client()

    temp_file <- withr::local_tempfile(fileext = ".R")
    writeLines(
        c(
            "file.path(",
            "fs::path_home('foo', "
        ),
        temp_file)

    client %>% did_open(temp_file)

    result <- client %>% respond_signature(temp_file, c(0, 10))
    expect_length(result$signatures, 1)
    expect_match(result$signatures[[1]]$label, "file\\.path\\(.*")
    expect_equal(result$signatures[[1]]$documentation$kind, "markdown")
    expect_match(result$signatures[[1]]$documentation$value,
        ".*Construct the path to a file from components in a platform-independent way.*")

    result <- client %>% respond_signature(temp_file, c(1, 21))
    expect_length(result$signatures, 1)
    expect_match(result$signatures[[1]]$label, "path_home\\(.*")
    expect_equal(result$signatures[[1]]$documentation$kind, "markdown")
    expect_match(result$signatures[[1]]$documentation$value,
        ".*`path_expand\\(\\)` performs tilde expansion on a path.*")
})

test_that("Signature of user function works", {
    skip_on_cran()
    client <- language_client()

    defn_file <- withr::local_tempfile(fileext = ".R")
    temp_file <- withr::local_tempfile(fileext = ".R")

    writeLines(c("foo <- function(x, y = 3) { x + y }"), defn_file)
    writeLines(c("foo(3, "), temp_file)

    client %>% did_open(defn_file) %>% did_open(temp_file)

    result <- client %>% respond_signature(
        temp_file, c(0, 7),
        retry_when = function(result) length(result) == 0 || length(result$signatures) == 0)
    expect_length(result$signatures, 1)
    expect_equal(result$signatures[[1]]$label, "foo(x, y = 3)")
})

test_that("Signature of user function works with semi-colon", {
    skip_on_cran()
    client <- language_client()

    defn_file <- withr::local_tempfile(fileext = ".R")
    temp_file <- withr::local_tempfile(fileext = ".R")

    writeLines(c("foo <- function(x, y = 3) { x + y };"), defn_file)
    writeLines(c("foo(3, "), temp_file)

    client %>% did_open(defn_file) %>% did_open(temp_file)

    result <- client %>% respond_signature(
        temp_file, c(0, 7),
        retry_when = function(result) length(result) == 0 || length(result$signatures) == 0)
    expect_length(result$signatures, 1)
    expect_equal(result$signatures[[1]]$label, "foo(x, y = 3)")
})

test_that("Signature in Rmarkdown works", {
    skip_on_cran()
    client <- language_client()

    temp_file <- withr::local_tempfile(fileext = ".Rmd")
    writeLines(
        c(
            "Title",
            "",
            "```{r}",
            "file.path(",
            "fs::path_home('foo', ",
            "```",
            "file.path("
        ),
        temp_file
    )

    client %>% did_open(temp_file)

    result <- client %>% respond_signature(temp_file, c(3, 10))
    expect_length(result$signatures, 1)
    expect_match(result$signatures[[1]]$label, "file\\.path\\(.*")

    result <- client %>% respond_signature(temp_file, c(4, 21))
    expect_length(result$signatures, 1)
    expect_match(result$signatures[[1]]$label, "path_home\\(.*")

    result <- client %>% respond_signature(temp_file, c(5, 10))
    expect_length(result$signatures, 0)
})

test_that("activeParameter is correctly computed", {
    skip_on_cran()
    client <- language_client()

    defn_file <- withr::local_tempfile(fileext = ".R")
    temp_file <- withr::local_tempfile(fileext = ".R")

    writeLines(c("foo <- function(a, b, c, d) { a + b + c + d }"), defn_file)
    writeLines(c("foo(1, "), temp_file)

    client %>% did_open(defn_file) %>% did_open(temp_file)

    # Test at first parameter (after opening parenthesis)
    result <- client %>% respond_signature(
        temp_file, c(0, 4),
        retry_when = function(result) length(result) == 0 || length(result$signatures) == 0)
    expect_equal(result$activeParameter, 0)
    expect_length(result$signatures[[1]]$parameters, 4)

    # Test at second parameter (after first comma)
    result <- client %>% respond_signature(
        temp_file, c(0, 7),
        retry_when = function(result) length(result) == 0 || length(result$signatures) == 0)
    expect_equal(result$activeParameter, 1)
    expect_length(result$signatures[[1]]$parameters, 4)

    # Test with more parameters
    writeLines(c("foo(1, 2, 3, "), temp_file)
    client %>% did_open(temp_file)
    
    result <- client %>% respond_signature(
        temp_file, c(0, 13),
        retry_when = function(result) length(result) == 0 || length(result$signatures) == 0)
    expect_equal(result$activeParameter, 3)
    expect_length(result$signatures[[1]]$parameters, 4)
})

test_that("activeParameter handles nested calls", {
    skip_on_cran()
    client <- language_client()

    defn_file <- withr::local_tempfile(fileext = ".R")
    temp_file <- withr::local_tempfile(fileext = ".R")

    writeLines(c("foo <- function(a, b, c) { a + b + c }"), defn_file)
    writeLines(c("foo(1, foo(2, 3), "), temp_file)

    client %>% did_open(defn_file) %>% did_open(temp_file)

    # Test at outer function's third parameter
    result <- client %>% respond_signature(
        temp_file, c(0, 18),
        retry_when = function(result) length(result) == 0 || length(result$signatures) == 0)
    expect_equal(result$activeParameter, 2)
})

test_that("activeParameter correctly handles named arguments", {
    skip_on_cran()
    client <- language_client()

    defn_file <- withr::local_tempfile(fileext = ".R")
    temp_file <- withr::local_tempfile(fileext = ".R")

    writeLines(c("fun <- function(x, y = 1, z = 2) { x + y + z }"), defn_file)
    
    # Test 1: Named argument z= should activate parameter z (index 2), not y
    writeLines(c("fun(1, z = "), temp_file)
    client %>% did_open(defn_file) %>% did_open(temp_file)
    
    result <- client %>% respond_signature(
        temp_file, c(0, 11),
        retry_when = function(result) length(result) == 0 || length(result$signatures) == 0)
    expect_equal(result$activeParameter, 2)
    expect_length(result$signatures[[1]]$parameters, 3)
    
    # Test 2: Named argument y= should activate parameter y (index 1)
    writeLines(c("fun(x = 1, y = "), temp_file)
    client %>% did_open(temp_file)
    
    result <- client %>% respond_signature(
        temp_file, c(0, 15),
        retry_when = function(result) length(result) == 0 || length(result$signatures) == 0)
    expect_equal(result$activeParameter, 1)
    
    # Test 3: Positional argument (no name) should use comma count
    writeLines(c("fun(1, 2, "), temp_file)
    client %>% did_open(temp_file)
    
    result <- client %>% respond_signature(
        temp_file, c(0, 10),
        retry_when = function(result) length(result) == 0 || length(result$signatures) == 0)
    expect_equal(result$activeParameter, 2)
    
    # Test 4: Named argument after skipping parameters
    writeLines(c("fun(z = "), temp_file)
    client %>% did_open(temp_file)
    
    result <- client %>% respond_signature(
        temp_file, c(0, 8),
        retry_when = function(result) length(result) == 0 || length(result$signatures) == 0)
    expect_equal(result$activeParameter, 2)
})

test_that("activeParameter correctly handles ... (ellipsis)", {
    skip_on_cran()
    client <- language_client()

    defn_file <- withr::local_tempfile(fileext = ".R")
    temp_file <- withr::local_tempfile(fileext = ".R")

    writeLines(c("fun <- function(a, ..., b = 1) { a + b }"), defn_file)
    
    # Test 1: Positional args after 'a' should stick to ... (index 1)
    writeLines(c("fun(1, 2, "), temp_file)
    client %>% did_open(defn_file) %>% did_open(temp_file)
    
    result <- client %>% respond_signature(
        temp_file, c(0, 10),
        retry_when = function(result) length(result) == 0 || length(result$signatures) == 0)
    expect_equal(result$activeParameter, 1)  # Should be ..., not b
    expect_length(result$signatures[[1]]$parameters, 3)
    
    # Test 2: More positional args should still stick to ...
    writeLines(c("fun(1, 2, 3, 4, "), temp_file)
    client %>% did_open(temp_file)
    
    result <- client %>% respond_signature(
        temp_file, c(0, 16),
        retry_when = function(result) length(result) == 0 || length(result$signatures) == 0)
    expect_equal(result$activeParameter, 1)  # Still ..., not b
    
    # Test 3: Named argument b= should activate parameter b (index 2)
    writeLines(c("fun(1, 2, 3, b = "), temp_file)
    client %>% did_open(temp_file)
    
    result <- client %>% respond_signature(
        temp_file, c(0, 17),
        retry_when = function(result) length(result) == 0 || length(result$signatures) == 0)
    expect_equal(result$activeParameter, 2)  # Explicitly named b
    
    # Test 4: First parameter before ...
    writeLines(c("fun("), temp_file)
    client %>% did_open(temp_file)
    
    result <- client %>% respond_signature(
        temp_file, c(0, 4),
        retry_when = function(result) length(result) == 0 || length(result$signatures) == 0)
    expect_equal(result$activeParameter, 0)  # Should be 'a'
})

test_that("activeParameter handles ... at different positions", {
    skip_on_cran()
    client <- language_client()

    defn_file <- withr::local_tempfile(fileext = ".R")
    temp_file <- withr::local_tempfile(fileext = ".R")

    # Test with ... at the end
    writeLines(c("fun2 <- function(a, b, ...) { a + b }"), defn_file)
    writeLines(c("fun2(1, 2, 3, 4, "), temp_file)
    client %>% did_open(defn_file) %>% did_open(temp_file)
    
    result <- client %>% respond_signature(
        temp_file, c(0, 17),
        retry_when = function(result) length(result) == 0 || length(result$signatures) == 0)
    expect_equal(result$activeParameter, 2)  # Should stick to ... (index 2)
    
    # Test with ... at the beginning
    writeLines(c("fun3 <- function(..., x, y = 1) { x + y }"), defn_file)
    writeLines(c("fun3(1, 2, "), temp_file)
    client %>% did_open(defn_file) %>% did_open(temp_file)
    
    result <- client %>% respond_signature(
        temp_file, c(0, 11),
        retry_when = function(result) length(result) == 0 || length(result$signatures) == 0)
    expect_equal(result$activeParameter, 0)  # Should stick to ... (index 0)
})