# ── Structure ─────────────────────────────────────────────────────────────────
test_that("calculate_i30 returns correct structure", {
  data <- data.frame(
    time  = as.POSIXct(c("2024-01-01 10:00", "2024-01-01 10:15",
                         "2024-01-01 10:30", "2024-01-01 10:45")),
    depth = c(5.2, 8.3, 4.1, 2.5)
  )
  
  result <- calculate_i30(data, "time", "depth")
  
  expect_type(result, "list")
  expect_named(result, c("i30", "total_rainfall", "duration",
                         "start_time", "end_time", "interval_type"))
  expect_type(result$i30, "double")
  expect_true(result$i30 >= 0)
})

# ── Equal intervals (auto-detected) ──────────────────────────────────────────
test_that("calculate_i30 handles equal intervals correctly (15-min)", {
  # 4 x 15-min intervals, 5mm each = 20mm total
  # Best 30-min window = any two consecutive intervals = 10mm/30min = 20 mm/hr
  data <- data.frame(
    time  = as.POSIXct(c("2024-01-01 10:00", "2024-01-01 10:15",
                         "2024-01-01 10:30", "2024-01-01 10:45")),
    depth = c(5, 5, 5, 5)
  )
  
  result <- calculate_i30(data, "time", "depth")
  
  expect_equal(result$i30, 20, tolerance = 0.5)
  expect_equal(result$total_rainfall, 20)
  expect_equal(result$interval_type, "equal")
})

test_that("calculate_i30 handles equal intervals correctly (30-min)", {
  # 4 x 30-min intervals, 10mm each
  # Best 30-min window = one interval = 10mm/30min = 20 mm/hr
  data <- data.frame(
    time  = as.POSIXct(c("2024-01-01 10:00", "2024-01-01 10:30",
                         "2024-01-01 11:00", "2024-01-01 11:30")),
    depth = c(10, 10, 10, 10)
  )
  
  result <- calculate_i30(data, "time", "depth")
  
  expect_equal(result$i30, 20, tolerance = 0.5)
  expect_equal(result$total_rainfall, 40)
  expect_equal(result$interval_type, "equal")
})

test_that("calculate_i30 handles equal intervals correctly (5-min)", {
  # 6 x 5-min intervals — best 30-min window = all 6 = 30mm/30min = 60 mm/hr
  data <- data.frame(
    time  = as.POSIXct(c("2024-01-01 10:00", "2024-01-01 10:05",
                         "2024-01-01 10:10", "2024-01-01 10:15",
                         "2024-01-01 10:20", "2024-01-01 10:25")),
    depth = c(5, 5, 5, 5, 5, 5)
  )
  
  result <- calculate_i30(data, "time", "depth")
  
  expect_equal(result$i30, 60, tolerance = 0.5)
  expect_equal(result$total_rainfall, 30)
  expect_equal(result$interval_type, "equal")
})

# ── Irregular intervals ───────────────────────────────────────────────────────
test_that("calculate_i30 handles irregular intervals correctly", {
  # Intense burst in first 20 min
  data <- data.frame(
    time  = as.POSIXct(c("2024-01-01 10:00", "2024-01-01 10:10",
                         "2024-01-01 10:20", "2024-01-01 11:00")),
    depth = c(2, 15, 13, 1)  # 28mm in 20 min
  )
  
  result <- calculate_i30(data, "time", "depth")
  
  # 28mm in 20 min fits in 30-min window → 28/20*60 = 84 mm/hr
  expect_equal(result$i30, 84, tolerance = 1)
  expect_equal(result$total_rainfall, 31)
  expect_equal(result$interval_type, "irregular")
})

test_that("calculate_i30 interpolates correctly when interval > 30 min", {
  # Single 60-min interval with 20mm → interpolated 30-min = 10mm = 20 mm/hr
  data <- data.frame(
    time  = as.POSIXct(c("2024-01-01 10:00", "2024-01-01 11:00")),
    depth = c(20, 0)
  )

  expect_warning(
    result <- calculate_i30(data, "time", "depth"),
    "Very few data points"
  )
  expect_equal(result$i30, 20, tolerance = 0.5)
})

# ── Explicit interval column ──────────────────────────────────────────────────
test_that("calculate_i30 works with explicit interval column", {
  data <- data.frame(
    time     = as.POSIXct(c("2024-01-01 10:00", "2024-01-01 10:20",
                            "2024-01-01 10:40")),
    depth    = c(10, 10, 10),
    interval = c(20, 20, 20)
  )
  
  result <- calculate_i30(data, "time", "depth", "interval")
  
  # 20mm in 40min → interpolated to 30min = 15mm/30min = 30 mm/hr
  expect_equal(result$i30, 30, tolerance = 1)
  expect_equal(result$interval_type, "explicit")
})

# ── Total rainfall ────────────────────────────────────────────────────────────
test_that("calculate_i30 calculates total rainfall correctly", {
  data <- data.frame(
    time  = as.POSIXct(c("2024-01-01 10:00", "2024-01-01 10:15",
                         "2024-01-01 10:30")),
    depth = c(5.5, 3.2, 1.8)
  )
  
  result <- calculate_i30(data, "time", "depth")
  
  expect_equal(result$total_rainfall, 10.5)
})

# ── Single data point ─────────────────────────────────────────────────────────
test_that("calculate_i30 handles single data point", {
  data <- data.frame(
    time  = as.POSIXct("2024-01-01 10:00"),
    depth = 10
  )

  # Single row triggers "Very few data points" validation warning
  expect_warning(
    result <- calculate_i30(data, "time", "depth"),
    "Very few data points"
  )
  # 10mm assumed over 30 min = 20 mm/hr
  expect_equal(result$i30, 20, tolerance = 0.5)
  expect_equal(result$total_rainfall, 10)
})

# ── Invalid data ──────────────────────────────────────────────────────────────
test_that("calculate_i30 fails on invalid data", {
  data <- data.frame(
    time  = as.POSIXct(c("2024-01-01 10:00", "2024-01-01 10:15")),
    depth = c(5, -2)
  )

  expect_error(calculate_i30(data, "time", "depth"), "Data validation failed")
})

# ── Zero rainfall ─────────────────────────────────────────────────────────────
test_that("calculate_i30 handles zero rainfall gracefully", {
  data <- data.frame(
    time  = as.POSIXct(c("2024-01-01 10:00", "2024-01-01 10:15",
                         "2024-01-01 10:30")),
    depth = c(0, 0, 0)
  )

  # All-zero depths triggers validation warning
  expect_warning(
    result <- calculate_i30(data, "time", "depth"),
    "All rainfall depths are zero"
  )
  expect_equal(result$i30, 0)
  expect_equal(result$total_rainfall, 0)
})

# ── Built-in dataset ──────────────────────────────────────────────────────────
test_that("calculate_i30 works with built-in rainfall_single dataset", {
  data("rainfall_single", package = "rainerosr")

  result <- calculate_i30(rainfall_single, "datetime", "rainfall_mm")

  expect_type(result, "list")
  expect_true(result$i30 > 0)
  expect_equal(result$total_rainfall, sum(rainfall_single$rainfall_mm))
})