defmodule Paraxial.Scan do
  @moduledoc false

  alias Paraxial.Finding

  def get_timestamp() do
    DateTime.utc_now()
  end

  def make_license(license_scan) do
    license_scan
    |> Enum.map(fn [dep, version, license] ->
      %Finding{
        source: "license_scan",
        content: %{
          "dependency" => dep,
          "version" => version,
          "license" => license,
          "reason" => "GPL software is not allowed for this site."
        }
      }
    end)
  end

  def make_sobelow(raw_scan) do
    # Input: The raw json output from a sobelow scan
    # Action: Use Jason (it's already in project) to parse, construct findings
    # Returns a list of findings
    case Jason.decode(raw_scan) do
      {:ok, scan_map} ->
        sobelow_get_findings(scan_map)

      {:error, _e} ->
        # Umbrella app
        many_scans = String.split(raw_scan, "\n\n") |> tl()

        Enum.map(many_scans, fn one_scan ->
          string_json = String.split(one_scan, "\n==>") |> hd()

          case Jason.decode(string_json) do
            {:ok, scan_map} ->
              sobelow_get_findings(scan_map)

            _ ->
              []
          end
        end)
        |> List.flatten()
    end
  end

  def sobelow_get_findings(scan_map) do
    # Input: The sobelow map like %{"findings" => %{"high_confidence" => ...}}
    # Output: A list of findings
    Enum.map(scan_map["findings"], fn {confidence, findings} ->
      Enum.map(findings, fn finding ->
        %Finding{
          source: "sobelow",
          content: Map.put(finding, "confidence", confidence)
        }
      end)
    end)
    |> List.flatten()
  end

  def make_deps(raw_deps, ignore \\ nil) do
    raw_deps
    |> String.split("\n\n")
    |> Enum.map(&dep_to_finding/1)
    |> List.flatten()
    |> filter_deps(ignore)
    |> Enum.filter(fn finding -> severity_exists?(finding) end)
  end

  # Advisory IDs as printed by hex.audit and deps.audit, e.g.
  # CVE-2026-32687, EEF-CVE-2026-43969, GHSA-p8f7-22gq-m7j9
  @vuln_id_regex ~r/^(EEF-CVE|CVE|GHSA)-/i

  def read_ignore_file() do
    if File.exists?("./.paraxial-ignore-deps") do
      parse_ignore_lines(File.read!("./.paraxial-ignore-deps"))
    else
      nil
    end
  end

  # Parses the contents of .paraxial-ignore-deps. Valid lines:
  #   hackney                    -> ignore the entire dependency
  #   postgrex CVE-2026-32687    -> ignore one vulnerability of one dependency
  # Blank lines and lines starting with # are skipped. Anything else is
  # collected under :malformed so the scan task can warn about it.
  def parse_ignore_lines(raw) do
    raw
    |> String.split("\n")
    |> Enum.map(&String.trim/1)
    |> Enum.reject(&(&1 == "" or String.starts_with?(&1, "#")))
    |> Enum.reduce(%{deps: [], vulns: [], malformed: []}, fn line, acc ->
      case String.split(line, " ", trim: true) do
        [dep] ->
          if vuln_id?(dep) do
            %{acc | malformed: acc.malformed ++ [line]}
          else
            %{acc | deps: acc.deps ++ [dep]}
          end

        [dep, vuln] ->
          if vuln_id?(vuln) and not vuln_id?(dep) do
            %{acc | vulns: acc.vulns ++ [{dep, vuln}]}
          else
            %{acc | malformed: acc.malformed ++ [line]}
          end

        _ ->
          %{acc | malformed: acc.malformed ++ [line]}
      end
    end)
  end

  defp vuln_id?(token), do: Regex.match?(@vuln_id_regex, token)

  def filter_deps(deps_list, nil), do: deps_list

  def filter_deps(deps_list, ignore) do
    {deps, vulns} = downcase_ignore(ignore)

    Enum.reject(deps_list, fn finding ->
      name = finding.content["Name"] |> to_string() |> String.trim() |> String.downcase()
      cve = finding.content["CVE"] |> to_string() |> String.downcase()
      url = finding.content["URL"] |> to_string() |> String.downcase()

      name in deps or
        Enum.any?(vulns, fn {dep, vuln} ->
          dep == name and (vuln == cve or String.contains?(url, vuln))
        end)
    end)
  end

  def filter_hex(findings, nil), do: findings

  def filter_hex(findings, ignore) do
    {deps, vulns} = downcase_ignore(ignore)

    Enum.reject(findings, fn finding ->
      name = finding.content["dependency"] |> to_string() |> String.downcase()

      ids =
        [finding.content["cve_id"] | Map.get(finding.content, "aka", [])]
        |> Enum.reject(&is_nil/1)
        |> Enum.map(&String.downcase/1)

      name in deps or
        Enum.any?(vulns, fn {dep, vuln} -> dep == name and vuln in ids end)
    end)
  end

  defp downcase_ignore(ignore) do
    deps = Enum.map(ignore.deps, &String.downcase/1)
    vulns = Enum.map(ignore.vulns, fn {d, v} -> {String.downcase(d), String.downcase(v)} end)
    {deps, vulns}
  end

  defp severity_exists?(fmap) do
    Enum.any?(Map.keys(fmap.content), fn key ->
      String.downcase(key) == "severity"
    end)
  end

  def fpart_to_tuple(fpart) do
    fpart
    |> String.split(":", parts: 2)
    |> List.to_tuple()
  end

  def dep_to_finding(dep_string) do
    finding = String.split(dep_string, "\n", trim: true)

    if length(finding) <= 2 do
      []
    else
      fmap =
        finding
        |> Enum.map(&fpart_to_tuple/1)
        # On some Elixir apps compilation metadata shows up here as tuples of 1
        # Filter out tuples that do not equal length 2 to avoid errors
        |> Enum.filter(fn tup -> tuple_size(tup) == 2 end)
        |> Map.new()

      %Finding{
        source: "deps.audit",
        content: fmap
      }
    end
  end

  def print_findings(findings) do
    Enum.map(findings, fn finding ->
      IO.puts("[Paraxial] #{finding.source}")
      Enum.each(Map.to_list(finding.content), fn {label, line} ->
        IO.puts("  #{label}: #{line}")
      end)
      IO.puts("")
    end)
  end

  # Input: Raw output from mix hex.audit
  # Returns a list of findings
  def make_hex(raw_hex, ignore \\ nil)
  def make_hex("No retired packages found\n", _ignore), do: []
  def make_hex("No retired packages found\nNo advisories found\n", _ignore), do: []

  def make_hex(raw_hex, ignore) do
    findings =
      if String.contains?(raw_hex, "Retired:\n") or String.contains?(raw_hex, "Advisories:\n") do
        make_hex_new(raw_hex)
      else
        make_hex_old(raw_hex)
      end

    filter_hex(findings, ignore)
  end

  # Parses the old hex.audit format (hex < 2.5.0):
  #   Dependency  Version  Retirement reason
  #   mojito      0.7.12   (deprecated) ...
  defp make_hex_old(raw_hex) do
    raw_lines = String.split(raw_hex, "\n", trim: true)
    raw_findings = tl(raw_lines)

    Enum.map(raw_findings, fn finding ->
      [dep, ver | reason] = String.split(finding, " ", trim: true)

      %Finding{
        source: "hex.audit",
        content: %{
          "dependency" => dep,
          "version" => ver,
          "reason" => Enum.join(reason, " ")
        }
      }
    end)
  end

  # Parses the new hex.audit format (hex >= 2.5.0) which has two sections:
  #
  # Retired:
  #   dep version - reason text
  #
  # Advisories:
  #   dep version - CVE-ID (SEVERITY)
  #     aka: alias1, alias2
  #     Description text
  #     https://url
  defp make_hex_new(raw_hex) do
    retired = parse_hex_retired_section(raw_hex)
    advisories = parse_hex_advisories_section(raw_hex)
    retired ++ advisories
  end

  defp parse_hex_retired_section(raw_hex) do
    case Regex.run(~r/Retired:\n(.*?)\n(?:Advisories:|\z)/s, raw_hex, capture: :all_but_first) do
      [block] ->
        block
        |> String.split("\n", trim: true)
        |> Enum.reject(&footer_line?/1)
        |> Enum.map(fn line ->
          # "  dep version - reason text"
          [dep, ver | rest] = String.split(String.trim(line), " ", trim: true)
          reason = rest |> Enum.drop_while(&(&1 == "-")) |> Enum.join(" ")

          %Finding{
            source: "hex.audit",
            content: %{
              "dependency" => dep,
              "version" => ver,
              "reason" => reason,
              "hex_type" => "retired"
            }
          }
        end)

      nil ->
        []
    end
  end

  defp parse_hex_advisories_section(raw_hex) do
    case Regex.run(~r/Advisories:\n(.*)/s, raw_hex, capture: :all_but_first) do
      [block] ->
        block
        |> String.split("\n\n", trim: true)
        |> Enum.reject(fn chunk -> footer_line?(String.trim(chunk)) end)
        |> Enum.flat_map(&parse_hex_advisory_block/1)

      nil ->
        []
    end
  end

  defp parse_hex_advisory_block(block) do
    lines =
      block
      |> String.split("\n", trim: true)
      |> Enum.reject(&footer_line?/1)
      |> Enum.map(&String.trim/1)

    case lines do
      [header | _rest] ->
        # Header: "dep version - CVE-ID" or "dep version - CVE-ID (SEVERITY)"
        # Lines are: [header, "aka: ...", "Title text", "https://url"]
        title = Enum.at(lines, 2)

        case Regex.run(~r/^(\S+)\s+(\S+)\s+-\s+(\S+)(?:\s+\((\w+)\))?$/, header) do
          [_, dep, ver, cve_id, severity] ->
            [%Finding{
              source: "hex.audit",
              content: %{
                "dependency" => dep,
                "version" => ver,
                "cve_id" => cve_id,
                "severity" => if(severity == "", do: nil, else: severity),
                "title" => title,
                "url" => find_url_in_lines(lines),
                "aka" => find_aka_in_lines(lines),
                "hex_type" => "advisory"
              }
            }]

          [_, dep, ver, cve_id] ->
            # No (SEVERITY) suffix in header line
            [%Finding{
              source: "hex.audit",
              content: %{
                "dependency" => dep,
                "version" => ver,
                "cve_id" => cve_id,
                "severity" => nil,
                "title" => title,
                "url" => find_url_in_lines(lines),
                "aka" => find_aka_in_lines(lines),
                "hex_type" => "advisory"
              }
            }]

          _ ->
            []
        end

      _ ->
        []
    end
  end

  # Parses "aka: CVE-2026-43969, GHSA-g2wm-735q-3f56" into a list of IDs
  defp find_aka_in_lines(lines) do
    case Enum.find(lines, fn l -> String.starts_with?(l, "aka:") end) do
      nil ->
        []

      aka_line ->
        aka_line
        |> String.trim_leading("aka:")
        |> String.split(",")
        |> Enum.map(&String.trim/1)
        |> Enum.reject(&(&1 == ""))
    end
  end

  defp find_url_in_lines(lines) do
    Enum.find(lines, fn l -> String.starts_with?(l, "http") end)
  end

  defp footer_line?(line) do
    line == "Found retired packages" or
      line == "Found packages with security advisories" or
      line == "No advisories found" or
      line == "No retired packages found"
  end
end