# Helper to create a minimal valid R package for testing pkg tools

local_minimal_package <- function(
  pkg_name = "testpkg",
  with_tests = TRUE,
  with_coverage = TRUE,
  .local_envir = parent.frame()
) {
  pkg_dir <- withr::local_tempdir(.local_envir = .local_envir)
  
  # Create package structure
  dir.create(file.path(pkg_dir, "R"), recursive = TRUE)
  if (with_tests) {
    dir.create(file.path(pkg_dir, "tests", "testthat"), recursive = TRUE)
  }
  dir.create(file.path(pkg_dir, "man"), recursive = TRUE)
  
  # Write minimal DESCRIPTION
  desc <- sprintf(
    "Package: %s
Version: 0.1.0
Title: Test Package
Description: A minimal package for testing.
Authors@R: person(\"Test\", \"User\", email = \"test@example.com\", role = c(\"aut\", \"cre\"))
License: MIT + file LICENSE
Encoding: UTF-8
Roxygen: list(markdown = TRUE)
RoxygenNote: 7.0.0
",
    pkg_name
  )
  writeLines(desc, file.path(pkg_dir, "DESCRIPTION"))
  
  # Write minimal NAMESPACE
  writeLines("# Generated by roxygen2: do not edit by hand", 
             file.path(pkg_dir, "NAMESPACE"))
  
  # Always write at least a simple R function for valid package structure
  if (with_coverage) {
    r_code <- "# Example function
#' Add two numbers
#'
#' @param x A number
#' @param y A number
#' @return The sum of x and y
#' @export
add_numbers <- function(x, y) {
  if (!is.numeric(x) || !is.numeric(y)) {
    stop(\"Both arguments must be numeric\")
  }
  x + y
}

#' Multiply two numbers (uncovered)
#'
#' @param x A number
#' @param y A number
#' @return The product of x and y
#' @export
multiply_numbers <- function(x, y) {
  if (!is.numeric(x) || !is.numeric(y)) {
    stop(\"Both arguments must be numeric\")
  }
  x * y
}
"
    writeLines(r_code, file.path(pkg_dir, "R", "example.R"))
    
    # Write corresponding test (only tests add_numbers, not multiply_numbers)
    if (with_tests) {
      test_code <- "test_that(\"add_numbers works\", {
  expect_equal(add_numbers(1, 2), 3)
  expect_equal(add_numbers(0, 0), 0)
  expect_equal(add_numbers(-1, 1), 0)
})

test_that(\"add_numbers validates input\", {
  expect_error(add_numbers(\"a\", 2), \"must be numeric\")
  expect_error(add_numbers(1, \"b\"), \"must be numeric\")
})
"
      writeLines(test_code, file.path(pkg_dir, "tests", "testthat", "test-example.R"))
      
      # Write testthat.R helper
      testthat_helper <- sprintf(
        "library(testthat)
library(%s)

test_check(\"%s\")
",
        pkg_name,
        pkg_name
      )
      writeLines(testthat_helper, file.path(pkg_dir, "tests", "testthat.R"))
    }
  } else {
    # Even without coverage tests, need a minimal R file for valid package
    r_code <- "# Minimal package content
#' A simple constant
#' @export
pkg_version <- \"0.1.0\"
"
    writeLines(r_code, file.path(pkg_dir, "R", "constants.R"))
  }
  
  invisible(pkg_dir)
}