# tests/testthat/test-ng_distance.R

test_that("input is validated", {
  expect_error(ng_distance(123, "Lagos"))
  expect_error(ng_distance("Lagos", TRUE))
  expect_error(ng_distance(), "'a' and 'b' must both be supplied")
  expect_error(ng_distance("Lagos", "Kaduna", unit = "Fahrenheit"),
               'should be one of "km", "miles"')
})

test_that("ng_distance returns correct value for known pair", {
  expect_equal(ng_distance("Lagos", "Abuja"), 761)
  expect_equal(ng_distance("Kano", "lagos"), 1139)
  expect_equal(ng_distance("Awka", "Asaba"), 44) 
  expect_equal(ng_distance("Gusau", "Dutse"), 416)
  expect_equal(ng_distance("Port Harcourt", "Calabar"), 196)
  expect_equal(ng_distance("Maiduguri", "Yola"), 436)
  expect_equal(ng_distance("Enugu", "Awka"), 62)
  expect_equal(ng_distance("Sokoto", "Maiduguri"), 1123)
})

test_that("distance matrix is symmetric", {
  expect_equal(ng_distance("Lagos", "Kano"), ng_distance("Kano", "Lagos"))
  expect_equal(ng_distance("Enugu", "Sokoto"), ng_distance("Sokoto", "Enugu"))
  expect_equal(ng_distance("Calabar", "Abuja"), ng_distance("Abuja", "Calabar"))
})

test_that("'Lagos' is equivalent to 'Ikeja'", {
  expect_identical(ng_distance("Lagos", "Abuja"), ng_distance("Ikeja", "Abuja"))
  expect_identical(ng_distance("Lagos", "Ikeja"), 0)
})

test_that("unit conversion to miles works", {
  expect_equal(ng_distance("Abuja", "Kano", unit = "miles"), 246.1)
})

test_that("case insensitivity works", {
  expect_equal(ng_distance("PORt HarCOurt", "EnUGu"),
               ng_distance("Port Harcourt", "Enugu"))
})

test_that("error on unknown city", {
  expect_error(ng_distance("Lagos", "FakeCity"), "not found")
  expect_error(ng_distance("Invalid", "Abuja"), "not found")
})

test_that("same city returns 0", {
  expect_equal(ng_distance("Abuja", "Abuja"), 0)
  expect_equal(ng_distance("ibadan", "Ibadan"), 0)
})

test_that("output is numeric with 1 decimal place", {
  d <- ng_distance("Jos", "Maiduguri")
  expect_type(d, "double")
  expect_length(d, 1)
  expect_equal(d, round(d, 1))
})

test_that("vector inputs return element-wise distances", {
  d <- ng_distance(c("Lagos", "Abuja"), c("Abuja", "Kano"))
  expect_length(d, 2)
  expect_equal(d[1], ng_distance("Lagos", "Abuja"))
  expect_equal(d[2], ng_distance("Abuja", "Kano"))
})

test_that("vector inputs with unit conversion work", {
  d <- ng_distance(c("Lagos", "Abuja"), c("Kano", "Enugu"), unit = "miles")
  expect_equal(d[1], ng_distance("Lagos", "Kano", unit = "miles"))
  expect_equal(d[2], ng_distance("Abuja", "Enugu", unit = "miles"))
})

test_that("unequal length vectors are rejected", {
  expect_error(ng_distance(c("Lagos", "Abuja"), "Kano"),
               "same length")
  expect_error(ng_distance("Lagos", c("Abuja", "Kano")),
               "same length")
  expect_error(ng_distance(c("Lagos", "Abuja", "Jos"), c("Kano", "Enugu")),
               "same length")
})

test_that("unknown city in vector input raises informative error", {
  expect_error(ng_distance(c("Lagos", "FakeCity"), c("Abuja", "Kano")),
               "FakeCity")
  expect_error(ng_distance(c("Lagos", "FakeCity"), c("Abuja", "Kano")),
               "position")
})