#!/usr/bin/env bash

set -euo pipefail

# Regenerates CREDITS from the license text of every Go module linked into the
# silo binary. The module set is what `go list -deps` reports for the main
# package, so test-only and tool dependencies stay out: CREDITS documents what
# a shipped binary actually contains. check-gen runs this and fails on a diff,
# which keeps CREDITS from drifting when go.mod changes.

script_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
repo_dir="$(cd "${script_dir}/.." && pwd)"
cd "${repo_dir}"

out_file="${1:-${repo_dir}/CREDITS}"
tmp_file="${out_file}.tmp"
trap 'rm -f "${tmp_file}"' EXIT

rule_dash='----------------------------------------------------------------'
rule_equal='================================================================'

# These modules repackage Go standard library code and publish no license
# file; their source files carry the Go Authors' BSD-style header pointing at
# the Go project license, so that text is reproduced for them.
stdlib_derived='github.com/minio/colorjson github.com/minio/csvparser github.com/minio/filepath'

is_stdlib_derived() {
  case " ${stdlib_derived} " in
    *" $1 "*) return 0 ;;
    *) return 1 ;;
  esac
}

# Command substitution strips trailing newlines; printf adds exactly one back,
# so every entry ends the same way regardless of how the license file ends.
emit_text() {
  printf '%s\n' "$(cat "$1")"
}

# The module cache must hold every dependency before .Dir can resolve.
go mod download

# The Go project license text is taken from the pinned golang.org/x/sys module
# rather than GOROOT: Homebrew's Go does not ship GOROOT/LICENSE, and the
# module copy is version-locked by go.mod, so the output cannot vary with the
# machine's toolchain packaging.
go_license="$(go list -m -f '{{.Dir}}' golang.org/x/sys)/LICENSE"
if [ ! -f "${go_license}" ]; then
  echo "Missing Go license text: ${go_license}" >&2
  exit 1
fi

{
  printf '%s\n' \
    'Silo bundles third-party software under the licenses reproduced below.' \
    'Generated by buildscripts/gen-credits.sh (make credits) from the Go' \
    'modules linked into the silo binary. Do not edit by hand.' \
    '' \
    "${rule_equal}" \
    ''
  printf '%s\n%s\n%s\n' 'Go (the standard library)' 'https://golang.org/' "${rule_dash}"
  emit_text "${go_license}"
  printf '\n%s\n\n' "${rule_equal}"

  # The dependency closure is GOOS/GOARCH-specific: platform-only modules
  # (darwin's go-m1cpu, windows' wmi, ...) enter and leave it with the host.
  # Pin the primary shipped target and the release build tags so regenerating
  # CREDITS produces identical output on every machine, including CI.
  GOOS=linux GOARCH=amd64 go list -deps -tags kqueue \
    -f '{{if and (not .Standard) .Module}}{{.Module.Path}}{{end}}' . \
    | LC_ALL=C sort -u \
    | grep -vx 'github.com/minio/minio' \
    | xargs go list -m -f '{{.Path}}|{{with .Replace}}{{.Path}}{{end}}|{{.Dir}}' \
    | while IFS='|' read -r path replacement dir; do
        if [ -z "${dir}" ] || [ ! -d "${dir}" ]; then
          echo "Module cache directory missing for ${path}" >&2
          exit 1
        fi

        name="${path}"
        url="https://${path}"
        # A same-path replace only pins a version; the annotation is for
        # dependencies actually served from a different repository.
        if [ -n "${replacement}" ] && [ "${replacement}" != "${path}" ]; then
          name="${path} (replaced by ${replacement})"
          url="https://${replacement}"
        fi

        printf '%s\n%s\n%s\n' "${name}" "${url}" "${rule_dash}"

        if is_stdlib_derived "${path}"; then
          printf '%s\n%s\n\n' \
            'This module repackages Go standard library code and publishes no' \
            'license file; the Go project license below applies per its file headers.'
          emit_text "${go_license}"
        else
          license_file=''
          for candidate in LICENSE LICENSE.txt LICENSE.md COPYING COPYING.txt LICENCE UNLICENSE; do
            if [ -f "${dir}/${candidate}" ]; then
              license_file="${dir}/${candidate}"
              break
            fi
          done
          if [ -z "${license_file}" ]; then
            echo "No license file found for ${path} in ${dir}" >&2
            exit 1
          fi
          emit_text "${license_file}"
        fi

        # Apache License 2.0 section 4(d) requires redistributing the NOTICE
        # file contents alongside the licensed work.
        for notice in NOTICE NOTICE.txt; do
          if [ -f "${dir}/${notice}" ]; then
            printf '\n%s\n\n' 'Bundled NOTICE file:'
            emit_text "${dir}/${notice}"
            break
          fi
        done

        printf '\n%s\n\n' "${rule_equal}"
      done
} > "${tmp_file}"

mv "${tmp_file}" "${out_file}"