require_relative "test_helper"
require "maptool/pmtiles_builder"
require "tmpdir"
require "fileutils"

# Network calls (Geofabrik downloads/HEADs, the mapterhorn manifest) are
# never exercised here — same "keep this offline/deterministic" reasoning
# test_helper.rb already gives for /api/plugins staying off the real
# Overpass API — build_offline/build_terrain take download_extract/
# fetch_manifest precisely so tests can swap those out. Fake `pmtiles`,
# `osmium`, and `java` binaries (PMTILES_BIN/OSMIUM_BIN/JAVA_BIN) stand in
# for the real tools, logging each invocation's subcommand/first arg to
# PMTILES_LOG so tests can assert on what actually got called (e.g. "was
# merge invoked, and with what").
#
# Country codes below are real ones from the vendored
# lib/maptool/data/europe_countries.geojson (Slovakia, Iceland, Spain) —
# chosen so their real bboxes fall cleanly inside/outside the fake
# manifest's chunk extents below, without needing a second fake geometry
# source.
class PmtilesBuilderTest < Minitest::Test
  def setup
    @data_dir = Dir.mktmpdir("maptool-pmtiles-test-data")
    @bin_dir = Dir.mktmpdir("maptool-pmtiles-test-bin")
    @log = File.join(@bin_dir, "pmtiles.log")

    # Output path: $3 for `extract SOURCE OUTPUT --region=... --maxzoom=...`
    # and `convert INPUT OUTPUT` alike; the *last* arg for `merge INPUT_1
    # [INPUT_2 ...] OUTPUT`, since its input count varies.
    @pmtiles_ok = File.join(@bin_dir, "pmtiles-ok")
    File.write(@pmtiles_ok, <<~SH)
      #!/bin/sh
      echo "$1 $2" >> "$PMTILES_LOG"
      case "$1" in
        merge)
          for last; do :; done
          echo fake > "$last"
          ;;
        *)
          echo fake > "$3"
          ;;
      esac
    SH
    File.chmod(0o755, @pmtiles_ok)

    @pmtiles_fail = File.join(@bin_dir, "pmtiles-fail")
    File.write(@pmtiles_fail, "#!/bin/sh\necho 'boom' >&2\nexit 1\n")
    File.chmod(0o755, @pmtiles_fail)

    # Mimics go-pmtiles' real extract failure mode: hundreds of progress
    # lines before the actual error — see command_output's tail-truncation.
    @pmtiles_fail_noisy = File.join(@bin_dir, "pmtiles-fail-noisy")
    File.write(@pmtiles_fail_noisy, <<~SH)
      #!/bin/sh
      i=0
      while [ "$i" -lt 200 ]; do
        echo "fetching $i dirs, $i chunks, 1 requests" >&2
        i=$((i + 1))
      done
      echo "stream error: stream ID 9; INTERNAL_ERROR" >&2
      exit 1
    SH
    File.chmod(0o755, @pmtiles_fail_noisy)

    # osmium merge PBF1 PBF2 ... -o OUTPUT — output is always "-o"'s next
    # arg, unlike pmtiles' varying-position output above.
    @osmium_ok = File.join(@bin_dir, "osmium-ok")
    File.write(@osmium_ok, <<~SH)
      #!/bin/sh
      echo "osmium $1" >> "$PMTILES_LOG"
      prev=""
      for arg; do
        if [ "$prev" = "-o" ]; then echo fake > "$arg"; fi
        prev="$arg"
      done
    SH
    File.chmod(0o755, @osmium_ok)

    # Same shape as osmium-ok, but fails on tags-filter specifically (the
    # first subcommand HikingTrails.extract runs) while still succeeding
    # on merge — lets a single-country build (which never calls merge)
    # exercise "hiking-trails extraction failed" without also breaking
    # offline.pmtiles' own osmium use in a multi-country test.
    @osmium_fail_tags_filter = File.join(@bin_dir, "osmium-fail-tags-filter")
    File.write(@osmium_fail_tags_filter, <<~SH)
      #!/bin/sh
      echo "osmium $1" >> "$PMTILES_LOG"
      if [ "$1" = "tags-filter" ]; then
        echo "boom" >&2
        exit 1
      fi
      prev=""
      for arg; do
        if [ "$prev" = "-o" ]; then echo fake > "$arg"; fi
        prev="$arg"
      done
    SH
    File.chmod(0o755, @osmium_fail_tags_filter)

    # Stands in for `java -jar planetiler.jar --osm-path=... --output=OUT`
    # — PLANETILER_JAR itself is irrelevant here (this fake ignores -jar's
    # argument entirely), only JAVA_BIN needs pointing at it.
    @java_ok = File.join(@bin_dir, "java-ok")
    File.write(@java_ok, <<~SH)
      #!/bin/sh
      echo "planetiler ${3%%=*}" >> "$PMTILES_LOG"
      for arg; do
        case "$arg" in
          --output=*) echo fake > "${arg#--output=}" ;;
        esac
      done
    SH
    File.chmod(0o755, @java_ok)

    @java_fail = File.join(@bin_dir, "java-fail")
    File.write(@java_fail, "#!/bin/sh\necho 'boom' >&2\nexit 1\n")
    File.chmod(0o755, @java_fail)

    @original_pmtiles_bin = ENV["PMTILES_BIN"]
    @original_osmium_bin = ENV["OSMIUM_BIN"]
    @original_java_bin = ENV["JAVA_BIN"]
    ENV["PMTILES_LOG"] = @log
    ENV["OSMIUM_BIN"] = @osmium_ok
    ENV["JAVA_BIN"] = @java_ok
    Maptool::PmtilesBuilder.reset!
  end

  def teardown
    FileUtils.remove_entry(@data_dir)
    FileUtils.remove_entry(@bin_dir)
    ENV["PMTILES_BIN"] = @original_pmtiles_bin
    ENV["OSMIUM_BIN"] = @original_osmium_bin
    ENV["JAVA_BIN"] = @original_java_bin
    ENV.delete("PMTILES_LOG")
    Maptool::PmtilesBuilder.reset!
  end

  # download_extract stub: writes a marker file (same "fake" content the
  # pmtiles/osmium/java fixtures use) instead of hitting Geofabrik, and
  # returns a fixed Last-Modified so sidecar-meta assertions are stable.
  # `calls` (an Array, shared across builds if the caller wants it) records
  # every URL actually downloaded, for asserting the per-country cache
  # skipped (or didn't skip) a re-download.
  def fake_download(last_modified: "Wed, 10 Sep 2026 08:00:01 GMT", calls: nil)
    ->(url, dest) {
      calls << url if calls
      File.write(dest, "fake")
      last_modified
    }
  end

  def log_lines
    File.exist?(@log) ? File.readlines(@log, chomp: true) : []
  end

  def select_regions(*codes)
    Maptool::PmtilesBuilder.set_selected_regions(@data_dir, codes)
  end

  # chunk-a covers Slovakia's real extent, chunk-b covers Iceland's —
  # Spain falls in neither, for the "no chunk intersects" case.
  def fake_manifest(chunk_a_md5: "md5-a")
    [
      { "name" => "planet.pmtiles", "url" => "https://example.com/planet.pmtiles", "md5sum" => "md5-planet", "min_lon" => -180.0, "min_lat" => -85.0, "max_lon" => 180.0, "max_lat" => 85.0, "min_zoom" => 0, "max_zoom" => 12 },
      { "name" => "chunk-a.pmtiles", "url" => "https://example.com/chunk-a.pmtiles", "md5sum" => chunk_a_md5, "min_lon" => 16.0, "min_lat" => 47.0, "max_lon" => 23.0, "max_lat" => 50.0, "min_zoom" => 13, "max_zoom" => 15 },
      { "name" => "chunk-b.pmtiles", "url" => "https://example.com/chunk-b.pmtiles", "md5sum" => "md5-b", "min_lon" => -25.0, "min_lat" => 63.0, "max_lon" => -13.0, "max_lat" => 67.0, "min_zoom" => 13, "max_zoom" => 15 },
    ]
  end

  def test_offline_and_terrain_status_start_idle
    assert_equal({ state: "idle" }, Maptool::PmtilesBuilder.offline_status)
    assert_equal({ state: "idle" }, Maptool::PmtilesBuilder.terrain_status)
  end

  # --- region selection ---

  def test_available_regions_includes_known_countries
    codes = Maptool::PmtilesBuilder.available_regions.map { |r| r[:code] }
    assert_includes codes, "SK"
    assert_includes codes, "IS"
  end

  def test_selected_regions_defaults_to_empty
    assert_empty Maptool::PmtilesBuilder.selected_regions(@data_dir)
  end

  def test_set_selected_regions_round_trips
    select_regions("SK", "AT")
    assert_equal ["SK", "AT"], Maptool::PmtilesBuilder.selected_regions(@data_dir)
  end

  def test_set_selected_regions_rejects_an_unknown_code
    assert_raises(Maptool::PmtilesBuilder::BuildError) { select_regions("SK", "XX") }
  end

  # --- offline.pmtiles ---

  def test_build_offline_raises_with_no_selection
    assert_raises(Maptool::PmtilesBuilder::BuildError) do
      Maptool::PmtilesBuilder.build_offline(data_dir: @data_dir, download_extract: fake_download)
    end
  end

  def test_build_offline_writes_the_file_and_reports_done
    select_regions("SK")
    thread = Maptool::PmtilesBuilder.build_offline(data_dir: @data_dir, download_extract: fake_download)
    thread.join

    assert_path_exists File.join(@data_dir, "offline.pmtiles")
    refute_path_exists File.join(@data_dir, "offline.tmp.pmtiles")
    assert_equal "done", Maptool::PmtilesBuilder.offline_status[:state]
    assert_equal ["planetiler --osm-path", "osmium tags-filter", "osmium add-locations-to-ways", "osmium cat"], log_lines
    assert_equal(
      { "sources" => [{ "code" => "SK", "slug" => "europe/slovakia", "last_modified" => "Wed, 10 Sep 2026 08:00:01 GMT" }] },
      Maptool::PmtilesBuilder.offline_meta(@data_dir),
    )
  end

  def test_build_offline_also_writes_a_hiking_trails_geojson
    select_regions("SK")
    thread = Maptool::PmtilesBuilder.build_offline(data_dir: @data_dir, download_extract: fake_download)
    thread.join

    # The fake osmium binary doesn't produce real OPL output, just
    # confirms the file lands and is valid (empty) GeoJSON — the real
    # parsing logic is covered by test_hiking_trails.rb against real OPL
    # fixtures.
    path = File.join(@data_dir, "hiking_trails.geojson")
    assert_path_exists path
    assert_equal({ "type" => "FeatureCollection", "features" => [] }, JSON.parse(File.read(path)))
  end

  # The actual reasoning: hiking trails are a bonus overlay bolted onto the
  # existing offline.pmtiles build, not the core map — an osmium hiccup on
  # this one step shouldn't take down an otherwise-successful build.
  def test_build_offline_still_succeeds_when_hiking_trails_extraction_fails
    select_regions("SK")
    ENV["OSMIUM_BIN"] = @osmium_fail_tags_filter
    thread = Maptool::PmtilesBuilder.build_offline(data_dir: @data_dir, download_extract: fake_download)
    thread.join

    assert_path_exists File.join(@data_dir, "offline.pmtiles")
    assert_equal "done", Maptool::PmtilesBuilder.offline_status[:state]
    refute_path_exists File.join(@data_dir, "hiking_trails.geojson")
    refute_path_exists "#{File.join(@data_dir, "hiking_trails.geojson")}.tmp"
  end

  # Two countries selected — osmium merge should run before planetiler,
  # each downloaded source recorded in the sidecar meta.
  def test_build_offline_merges_multiple_selected_countries
    select_regions("SK", "AT")
    thread = Maptool::PmtilesBuilder.build_offline(data_dir: @data_dir, download_extract: fake_download)
    thread.join

    assert_equal "done", Maptool::PmtilesBuilder.offline_status[:state]
    assert_equal(
      [
        "osmium merge", "planetiler --osm-path",
        "osmium tags-filter", "osmium add-locations-to-ways", "osmium cat", # SK's own hiking-trails extraction
        "osmium tags-filter", "osmium add-locations-to-ways", "osmium cat", # AT's own
      ],
      log_lines,
    )
    codes = Maptool::PmtilesBuilder.offline_meta(@data_dir)["sources"].map { |s| s["code"] }
    assert_equal %w[SK AT], codes
  end

  # The actual bug report this covers: hitting "Apply" after tweaking the
  # region selection used to re-download every selected country's .osm.pbf
  # from scratch, even ones already fetched by an earlier build.
  def test_build_offline_skips_redownloading_an_unchanged_cached_country
    select_regions("SK")
    calls = []
    Maptool::PmtilesBuilder.build_offline(data_dir: @data_dir, download_extract: fake_download(calls: calls)).join
    assert_equal 1, calls.size

    Maptool::PmtilesBuilder.build_offline(
      data_dir: @data_dir,
      download_extract: fake_download(calls: calls),
      fetch_last_modified: ->(_url) { "Wed, 10 Sep 2026 08:00:01 GMT" },
    ).join

    assert_equal 1, calls.size
    assert_equal "done", Maptool::PmtilesBuilder.offline_status[:state]
  end

  def test_build_offline_redownloads_a_country_whose_extract_changed
    select_regions("SK")
    calls = []
    Maptool::PmtilesBuilder.build_offline(data_dir: @data_dir, download_extract: fake_download(calls: calls)).join

    Maptool::PmtilesBuilder.build_offline(
      data_dir: @data_dir,
      download_extract: fake_download(calls: calls, last_modified: "Thu, 11 Sep 2026 08:00:01 GMT"),
      fetch_last_modified: ->(_url) { "Thu, 11 Sep 2026 08:00:01 GMT" },
    ).join

    assert_equal 2, calls.size
  end

  # A cache-freshness check that itself fails (Geofabrik unreachable) should
  # fall back to re-downloading rather than aborting the build.
  def test_build_offline_redownloads_when_the_cache_check_fails
    select_regions("SK")
    calls = []
    Maptool::PmtilesBuilder.build_offline(data_dir: @data_dir, download_extract: fake_download(calls: calls)).join

    fetch_last_modified = ->(_url) { raise Maptool::PmtilesBuilder::BuildError, "could not reach geofabrik" }
    Maptool::PmtilesBuilder.build_offline(
      data_dir: @data_dir,
      download_extract: fake_download(calls: calls),
      fetch_last_modified: fetch_last_modified,
    ).join

    assert_equal 2, calls.size
    assert_equal "done", Maptool::PmtilesBuilder.offline_status[:state]
  end

  def test_build_offline_only_downloads_a_newly_added_country
    select_regions("SK")
    calls = []
    Maptool::PmtilesBuilder.build_offline(data_dir: @data_dir, download_extract: fake_download(calls: calls)).join

    select_regions("SK", "AT")
    Maptool::PmtilesBuilder.build_offline(
      data_dir: @data_dir,
      download_extract: fake_download(calls: calls),
      fetch_last_modified: ->(_url) { "Wed, 10 Sep 2026 08:00:01 GMT" },
    ).join

    assert_equal 1, calls.count { |url| url.include?("slovakia") }
    assert_equal 1, calls.count { |url| url.include?("austria") }
  end

  # offline_status[:step] should say which country is in flight right now
  # and which of the current build's selection are already done/still
  # pending — not just "running since X".
  def test_build_offline_reports_progress_step_while_running
    select_regions("SK", "AT")
    started = Queue.new
    gate = Queue.new
    download_extract = ->(url, dest) {
      started.push(url)
      gate.pop
      File.write(dest, "fake")
      "Wed, 10 Sep 2026 08:00:01 GMT"
    }
    thread = Maptool::PmtilesBuilder.build_offline(data_dir: @data_dir, download_extract: download_extract)

    started.pop
    assert_equal "fetching SK (1/2) — pending: AT", Maptool::PmtilesBuilder.offline_status[:step]
    gate.push(:go)

    started.pop
    assert_equal "fetching AT (2/2) — done: SK", Maptool::PmtilesBuilder.offline_status[:step]
    gate.push(:go)

    thread.join
    assert_nil Maptool::PmtilesBuilder.offline_status[:step]
  end

  def test_delete_offline_data_removes_the_file_meta_and_cache
    select_regions("SK")
    Maptool::PmtilesBuilder.build_offline(data_dir: @data_dir, download_extract: fake_download).join
    assert_path_exists File.join(@data_dir, "offline.pmtiles")
    assert_path_exists File.join(@data_dir, "geofabrik_cache", "SK.osm.pbf")

    Maptool::PmtilesBuilder.delete_offline_data(@data_dir)

    refute_path_exists File.join(@data_dir, "offline.pmtiles")
    refute_path_exists File.join(@data_dir, "geofabrik_cache")
    assert_nil Maptool::PmtilesBuilder.offline_meta(@data_dir)
  end

  def test_delete_offline_data_is_a_noop_when_nothing_was_built
    Maptool::PmtilesBuilder.delete_offline_data(@data_dir) # should not raise
  end

  def test_delete_offline_data_raises_while_a_build_is_running
    select_regions("SK")
    gate = Queue.new
    thread = Maptool::PmtilesBuilder.build_offline(data_dir: @data_dir, download_extract: ->(_url, _dest) { gate.pop })

    assert_raises(Maptool::PmtilesBuilder::BuildError) { Maptool::PmtilesBuilder.delete_offline_data(@data_dir) }
  ensure
    gate.push("unused")
    thread&.join
  end

  def test_delete_cached_extract_removes_only_that_country
    select_regions("SK", "AT")
    Maptool::PmtilesBuilder.build_offline(data_dir: @data_dir, download_extract: fake_download).join

    Maptool::PmtilesBuilder.delete_cached_extract(@data_dir, "SK")

    refute_path_exists File.join(@data_dir, "geofabrik_cache", "SK.osm.pbf")
    assert_path_exists File.join(@data_dir, "geofabrik_cache", "AT.osm.pbf")
  end

  def test_delete_terrain_data_removes_the_file_and_meta
    select_regions("ES")
    ENV["PMTILES_BIN"] = @pmtiles_ok
    thread = Maptool::PmtilesBuilder.build_terrain(data_dir: @data_dir, fetch_manifest: -> { fake_manifest })
    thread.join
    assert_path_exists File.join(@data_dir, "terrain.pmtiles")

    Maptool::PmtilesBuilder.delete_terrain_data(@data_dir)

    refute_path_exists File.join(@data_dir, "terrain.pmtiles")
    assert_nil Maptool::PmtilesBuilder.terrain_meta(@data_dir)
  end

  def test_cached_extracts_is_empty_before_any_download
    assert_empty Maptool::PmtilesBuilder.cached_extracts(@data_dir)
  end

  # Deliberately still selected — cached_extracts reflects the cache on
  # disk, not the current selection or the last build's own meta (see
  # cached_extracts' own comment for why those three can all disagree).
  def test_cached_extracts_lists_what_was_downloaded
    select_regions("SK", "AT")
    Maptool::PmtilesBuilder.build_offline(data_dir: @data_dir, download_extract: fake_download).join

    extracts = Maptool::PmtilesBuilder.cached_extracts(@data_dir)
    assert_equal %w[AT SK], extracts.map { |e| e["code"] }
    assert_equal [4, 4], extracts.map { |e| e["size"] } # "fake".bytesize
    assert_equal ["Wed, 10 Sep 2026 08:00:01 GMT"] * 2, extracts.map { |e| e["last_modified"] }
  end

  def test_offline_meta_is_nil_before_any_build
    assert_nil Maptool::PmtilesBuilder.offline_meta(@data_dir)
  end

  def test_offline_update_available_is_nil_before_any_build
    assert_nil Maptool::PmtilesBuilder.offline_update_available?(@data_dir, fetch_last_modified: ->(_url) { "unused" })
  end

  def test_offline_update_available_is_false_when_unchanged
    select_regions("SK")
    Maptool::PmtilesBuilder.build_offline(data_dir: @data_dir, download_extract: fake_download).join

    refute Maptool::PmtilesBuilder.offline_update_available?(@data_dir, fetch_last_modified: ->(_url) { "Wed, 10 Sep 2026 08:00:01 GMT" })
  end

  def test_offline_update_available_is_true_when_a_newer_extract_exists
    select_regions("SK")
    Maptool::PmtilesBuilder.build_offline(data_dir: @data_dir, download_extract: fake_download).join

    assert Maptool::PmtilesBuilder.offline_update_available?(@data_dir, fetch_last_modified: ->(_url) { "Thu, 11 Sep 2026 08:00:01 GMT" })
  end

  # Same recorded source, but the selection has since grown — recorded
  # sources no longer match what the current selection would need.
  def test_offline_update_available_is_true_when_the_selection_grew
    select_regions("SK")
    Maptool::PmtilesBuilder.build_offline(data_dir: @data_dir, download_extract: fake_download).join

    select_regions("SK", "AT")
    assert Maptool::PmtilesBuilder.offline_update_available?(@data_dir, fetch_last_modified: ->(_url) { "Wed, 10 Sep 2026 08:00:01 GMT" })
  end

  def test_offline_update_available_is_nil_when_geofabrik_is_unreachable
    select_regions("SK")
    Maptool::PmtilesBuilder.build_offline(data_dir: @data_dir, download_extract: fake_download).join

    fetch_last_modified = ->(_url) { raise Maptool::PmtilesBuilder::BuildError, "could not reach geofabrik" }
    assert_nil Maptool::PmtilesBuilder.offline_update_available?(@data_dir, fetch_last_modified: fetch_last_modified)
  end

  def test_build_offline_reports_an_error_status_on_non_zero_exit
    select_regions("SK")
    ENV["JAVA_BIN"] = @java_fail
    thread = Maptool::PmtilesBuilder.build_offline(data_dir: @data_dir, download_extract: fake_download)
    thread.join

    refute_path_exists File.join(@data_dir, "offline.pmtiles")
    status = Maptool::PmtilesBuilder.offline_status
    assert_equal "error", status[:state]
    assert_match(/exited with status/, status[:message])
  end

  def test_build_offline_reports_a_clear_error_when_planetiler_is_missing
    select_regions("SK")
    ENV["JAVA_BIN"] = File.join(@bin_dir, "does-not-exist")
    thread = Maptool::PmtilesBuilder.build_offline(data_dir: @data_dir, download_extract: fake_download)
    thread.join

    status = Maptool::PmtilesBuilder.offline_status
    assert_equal "error", status[:state]
    assert_match(/Java and planetiler\.jar installed/, status[:message])
  end

  # download_extract blocks on a Queue so the build is deterministically
  # still "running" when the second call happens, rather than racing a real
  # one to see which state wins.
  def test_build_offline_raises_when_one_is_already_running
    select_regions("SK")
    gate = Queue.new
    thread = Maptool::PmtilesBuilder.build_offline(data_dir: @data_dir, download_extract: ->(_url, _dest) { gate.pop })

    assert_raises(Maptool::PmtilesBuilder::BuildError) do
      Maptool::PmtilesBuilder.build_offline(data_dir: @data_dir, download_extract: fake_download)
    end
  ensure
    gate.push("Wed, 10 Sep 2026 08:00:01 GMT")
    thread&.join
  end

  # --- terrain.pmtiles ---

  def test_build_terrain_raises_with_no_selection
    assert_raises(Maptool::PmtilesBuilder::BuildError) do
      Maptool::PmtilesBuilder.build_terrain(data_dir: @data_dir, fetch_manifest: -> { fake_manifest })
    end
  end

  # Spain intersects neither fake chunk — only planet.pmtiles matches, so
  # this should be a single extract straight to the final path, no merge.
  def test_build_terrain_extracts_only_planet_when_no_chunk_intersects
    select_regions("ES")
    ENV["PMTILES_BIN"] = @pmtiles_ok
    thread = Maptool::PmtilesBuilder.build_terrain(data_dir: @data_dir, fetch_manifest: -> { fake_manifest })
    thread.join

    assert_path_exists File.join(@data_dir, "terrain.pmtiles")
    assert_equal "done", Maptool::PmtilesBuilder.terrain_status[:state]
    assert_equal ["extract https://example.com/planet.pmtiles"], log_lines
  end

  # Slovakia intersects chunk-a only — planet.pmtiles (always) plus that
  # one chunk get extracted, then merged.
  def test_build_terrain_extracts_and_merges_a_single_intersecting_chunk
    select_regions("SK")
    ENV["PMTILES_BIN"] = @pmtiles_ok
    thread = Maptool::PmtilesBuilder.build_terrain(data_dir: @data_dir, fetch_manifest: -> { fake_manifest })
    thread.join

    assert_path_exists File.join(@data_dir, "terrain.pmtiles")
    assert_equal "done", Maptool::PmtilesBuilder.terrain_status[:state]
    extracted = log_lines.select { |line| line.start_with?("extract ") }
    merged = log_lines.select { |line| line.start_with?("merge ") }
    assert_equal ["extract https://example.com/planet.pmtiles", "extract https://example.com/chunk-a.pmtiles"], extracted
    assert_equal 1, merged.size
    assert_equal(
      { "sources" => [{ "name" => "planet.pmtiles", "md5sum" => "md5-planet" }, { "name" => "chunk-a.pmtiles", "md5sum" => "md5-a" }] },
      Maptool::PmtilesBuilder.terrain_meta(@data_dir),
    )
  end

  def test_terrain_meta_is_nil_before_any_build
    assert_nil Maptool::PmtilesBuilder.terrain_meta(@data_dir)
  end

  def test_terrain_update_available_is_false_when_unchanged
    select_regions("SK")
    ENV["PMTILES_BIN"] = @pmtiles_ok
    Maptool::PmtilesBuilder.build_terrain(data_dir: @data_dir, fetch_manifest: -> { fake_manifest }).join

    refute Maptool::PmtilesBuilder.terrain_update_available?(@data_dir, fetch_manifest: -> { fake_manifest })
  end

  # Same selection, but chunk-a's md5sum has since changed upstream.
  def test_terrain_update_available_is_true_when_a_source_changed
    select_regions("SK")
    ENV["PMTILES_BIN"] = @pmtiles_ok
    Maptool::PmtilesBuilder.build_terrain(data_dir: @data_dir, fetch_manifest: -> { fake_manifest }).join

    assert Maptool::PmtilesBuilder.terrain_update_available?(@data_dir, fetch_manifest: -> { fake_manifest(chunk_a_md5: "md5-a-v2") })
  end

  # Same recorded sources, but the selection has since grown to also cover
  # chunk-b — recorded sources no longer match what the current selection
  # would need.
  def test_terrain_update_available_is_true_when_the_selection_grew
    select_regions("SK")
    ENV["PMTILES_BIN"] = @pmtiles_ok
    Maptool::PmtilesBuilder.build_terrain(data_dir: @data_dir, fetch_manifest: -> { fake_manifest }).join

    select_regions("SK", "IS")
    assert Maptool::PmtilesBuilder.terrain_update_available?(@data_dir, fetch_manifest: -> { fake_manifest })
  end

  # Slovakia + Iceland together intersect both fake chunks — planet + both
  # chunks, one 3-way merge.
  def test_build_terrain_merges_multiple_intersecting_chunks
    select_regions("SK", "IS")
    ENV["PMTILES_BIN"] = @pmtiles_ok
    thread = Maptool::PmtilesBuilder.build_terrain(data_dir: @data_dir, fetch_manifest: -> { fake_manifest })
    thread.join

    assert_equal "done", Maptool::PmtilesBuilder.terrain_status[:state]
    extracted = log_lines.count { |line| line.start_with?("extract ") }
    assert_equal 3, extracted # planet + chunk-a + chunk-b
    assert_equal 1, log_lines.count { |line| line.start_with?("merge ") }
  end

  def test_build_terrain_reports_a_clear_error_when_the_manifest_is_missing_planet
    select_regions("ES")
    ENV["PMTILES_BIN"] = @pmtiles_ok
    thread = Maptool::PmtilesBuilder.build_terrain(data_dir: @data_dir, fetch_manifest: -> { fake_manifest.reject { |i| i["name"] == "planet.pmtiles" } })
    thread.join

    status = Maptool::PmtilesBuilder.terrain_status
    assert_equal "error", status[:state]
    assert_match(/missing planet\.pmtiles/, status[:message])
  end

  def test_build_terrain_reports_an_error_status_on_non_zero_exit
    select_regions("ES")
    ENV["PMTILES_BIN"] = @pmtiles_fail
    thread = Maptool::PmtilesBuilder.build_terrain(data_dir: @data_dir, fetch_manifest: -> { fake_manifest })
    thread.join

    refute_path_exists File.join(@data_dir, "terrain.pmtiles")
    status = Maptool::PmtilesBuilder.terrain_status
    assert_equal "error", status[:state]
    assert_match(/exited with status/, status[:message])
  end

  # The real trigger for this: a Mapterhorn extract that failed after ~7000
  # progress lines, producing a 500k+ character status[:message] that was
  # unreadable in the web UI.
  def test_build_terrain_truncates_a_noisy_command_failure
    select_regions("ES")
    ENV["PMTILES_BIN"] = @pmtiles_fail_noisy
    thread = Maptool::PmtilesBuilder.build_terrain(data_dir: @data_dir, fetch_manifest: -> { fake_manifest })
    thread.join

    status = Maptool::PmtilesBuilder.terrain_status
    assert_equal "error", status[:state]
    assert_match(/\(\d+ earlier lines omitted\)/, status[:message])
    assert_match(/stream error: stream ID 9/, status[:message])
    assert_operator status[:message].length, :<, 5000
  end

  def test_build_terrain_raises_when_one_is_already_running
    select_regions("ES")
    ENV["PMTILES_BIN"] = @pmtiles_ok
    gate = Queue.new
    thread = Maptool::PmtilesBuilder.build_terrain(data_dir: @data_dir, fetch_manifest: -> { gate.pop })

    assert_raises(Maptool::PmtilesBuilder::BuildError) do
      Maptool::PmtilesBuilder.build_terrain(data_dir: @data_dir, fetch_manifest: -> { "unused" })
    end
  ensure
    gate.push(fake_manifest)
    thread&.join
  end
end