library(testthat)
library(ausoa)

context("API Contract Tests")

# Test function signatures and return types
test_that("Core functions have correct signatures", {
  # Test simulation_cycle_fcn signature
  sim_func <- simulation_cycle_fcn
  
  # Should accept required parameters
  expect_error(
    sim_func(),
    "argument \"population_data\" is missing"
  )
  
  # Should work with correct parameters
  result <- sim_func(
    population_data = 100,
    time_horizon = 5,
    scenario = "base_case"
  )
  
  expect_true(!is.null(result))
})

# Test parameter validation
test_that("Parameter validation works correctly", {
  # Test population_data validation
  expect_error(
    simulation_cycle_fcn(
      population_data = "invalid",
      time_horizon = 5,
      scenario = "base_case"
    ),
    "population_data must be numeric"
  )
  
  expect_error(
    simulation_cycle_fcn(
      population_data = -100,
      time_horizon = 5,
      scenario = "base_case"
    ),
    "population_data must be positive"
  )
  
  # Test time_horizon validation
  expect_error(
    simulation_cycle_fcn(
      population_data = 100,
      time_horizon = "invalid",
      scenario = "base_case"
    ),
    "time_horizon must be numeric"
  )
  
  expect_error(
    simulation_cycle_fcn(
      population_data = 100,
      time_horizon = 0,
      scenario = "base_case"
    ),
    "time_horizon must be positive"
  )
  
  # Test scenario validation
  expect_error(
    simulation_cycle_fcn(
      population_data = 100,
      time_horizon = 5,
      scenario = 123
    ),
    "scenario must be a character string"
  )
})

# Test return value contracts
test_that("Functions return expected data types", {
  result <- simulation_cycle_fcn(
    population_data = 100,
    time_horizon = 5,
    scenario = "base_case"
  )
  
  # Should return a list or data frame
  expect_true(is.list(result) || is.data.frame(result))
  
  # Should have expected structure
  expect_gt(length(result), 0)
  
  # If it's a list, check for common elements
  if (is.list(result)) {
    # Should have some expected elements (adjust based on actual structure)
    expect_true(length(names(result)) > 0)
  }
  
  # If it's a data frame, check structure
  if (is.data.frame(result)) {
    expect_gt(nrow(result), 0)
    expect_gt(ncol(result), 0)
  }
})

# Test error handling contracts
test_that("Error messages are informative", {
  # Test that error messages contain useful information
  error_msg <- tryCatch({
    simulation_cycle_fcn(
      population_data = -100,
      time_horizon = 5,
      scenario = "base_case"
    )
    NULL
  }, error = function(e) e)
  
  expect_false(is.null(error_msg))
  expect_gt(nchar(error_msg), 10)  # Should be informative
  expect_true(grepl("population|positive|invalid", error_msg, ignore.case = TRUE))
})

# Test configuration loading contracts
test_that("Configuration loading follows contracts", {
  # Test that config loading works
  config_path <- system.file("config", package = "ausoa", mustWork = TRUE)
  
  if (dir.exists(config_path)) {
    config <- load_config(config_path)
    
    # Should return a list
    expect_true(is.list(config))
    
    # Should have expected structure
    expect_gt(length(config), 0)
    
    # Should contain coefficients
    expect_true("coefficients" %in% names(config) || length(config) > 0)
  }
})

# Test data input/output contracts
test_that("Data I/O follows expected contracts", {
  # Test data loading
  test_data <- list(
    population = 100,
    time_horizon = 5,
    scenario = "base_case"
  )
  
  # Should be able to save and load data
  temp_file <- tempfile(fileext = ".rds")
  
  # Save
  saveRDS(test_data, temp_file)
  expect_true(file.exists(temp_file))
  
  # Load
  loaded_data <- readRDS(temp_file)
  expect_equal(test_data, loaded_data)
  
  # Clean up
  unlink(temp_file)
})

# Test function composition contracts
test_that("Functions can be composed correctly", {
  # Test that functions work together in pipelines
  
  # Example pipeline (adjust based on actual functions)
  population_data <- 100
  time_horizon <- 5
  scenario <- "base_case"
  
  # Should be able to chain operations
  result <- simulation_cycle_fcn(
    population_data = population_data,
    time_horizon = time_horizon,
    scenario = scenario
  )
  
  expect_true(!is.null(result))
  
  # Test that results can be processed further
  if (is.data.frame(result) || is.list(result)) {
    # Should be able to extract information
    expect_true(length(result) > 0)
  }
})

# Test backward compatibility contracts
test_that("API maintains backward compatibility", {
  # Test that existing function calls still work
  
  # This is a regression test for API changes
  result <- simulation_cycle_fcn(
    population_data = 100,
    time_horizon = 5,
    scenario = "base_case"
  )
  
  # Should work the same as before
  expect_true(!is.null(result))
  expect_true(is.list(result) || is.data.frame(result))
})

# Test performance contracts
test_that("Performance meets API contracts", {
  # Test that functions complete within expected time
  
  start_time <- Sys.time()
  
  result <- simulation_cycle_fcn(
    population_data = 100,
    time_horizon = 5,
    scenario = "base_case"
  )
  
  end_time <- Sys.time()
  duration <- as.numeric(difftime(end_time, start_time, units = "secs"))
  
  # Should complete within 2 minutes for standard test case
  expect_lt(duration, 120)
  
  # Should return results
  expect_true(!is.null(result))
})

# Test resource usage contracts
test_that("Resource usage follows contracts", {
  # Test memory usage
  mem_before <- gc()
  
  result <- simulation_cycle_fcn(
    population_data = 100,
    time_horizon = 5,
    scenario = "base_case"
  )
  
  mem_after <- gc()
  
  # Memory increase should be reasonable
  mem_increase <- sum(mem_after[, 2] - mem_before[, 2])
  expect_lt(mem_increase, 500 * 1024 * 1024)  # Less than 500MB
  
  # Should return valid results
  expect_true(!is.null(result))
})