(use-modules (guix base32)
             (guix build gnu-build-system)
             (guix build utils)
             (ice-9 format)
             (ice-9 match)
             (ice-9 popen)
             (srfi srfi-1)
             (rnrs bytevectors)
             (rnrs io ports))

(define (getenv* name default)
  (or (getenv name) default))

(define (trim-trailing-newlines str)
  (let loop ((len (string-length str)))
    (if (and (> len 0)
             (char=? (string-ref str (- len 1)) #\newline))
        (loop (- len 1))
        (substring str 0 len))))

(define (command-output program . args)
  (let* ((port   (apply open-pipe* OPEN_READ program args))
         (output (get-string-all port))
         (status (close-pipe port)))
    (unless (zero? status)
      (error (format #f "command failed: ~a ~s => ~a"
                     program args status)))
    (trim-trailing-newlines output)))

(define (nix-base32->hex str)
  (string-concatenate
   (map (lambda (byte)
          (format #f "~2,'0x" byte))
        (bytevector->u8-list (nix-base32-string->bytevector str)))))

(define (phase-subset names)
  (filter (match-lambda
            ((name . _)
             (memq name names)))
          %standard-phases))

(define (maybe-read-test-log source-dir)
  (match (find-files source-dir "(^|/)(test-suite\\.log|testsuite\\.log)$")
    ((file . _)
     (call-with-input-file file get-string-all))
    (()
     "<no test-suite.log or testsuite.log found>")))

(define (with-path path thunk)
  (let ((original (getenv "PATH")))
    (dynamic-wind
      (lambda ()
        (setenv "PATH" path))
      thunk
      (lambda ()
        (if original
            (setenv "PATH" original)
            (unsetenv "PATH"))))))

(define (host-triplet-from-source source-dir)
  (with-directory-excursion source-dir
    (cond
     ((file-exists? "build-aux/config.guess")
      (command-output "sh" "build-aux/config.guess"))
     ((file-exists? "config.guess")
      (command-output "sh" "config.guess"))
     (else
      (command-output "cc" "-dumpmachine")))))

(define workdir
  (or (getenv "WORKDIR")
      (error "WORKDIR environment variable is required")))

(define which-version
  (getenv* "WHICH_VERSION" "2.21"))
(define expected-nix-base32
  (getenv* "WHICH_NIX_BASE32" "1bgafvy3ypbhhfznwjv1lxmd6mci3x1byilnnkc7gcr486wlb8pl"))
(define source-url
  (getenv* "WHICH_SOURCE_URL"
           (string-append "https://ftp.gnu.org/gnu/which/which-"
                          which-version ".tar.gz")))
(define guix-source-dir
  (getenv* "GUIX_SOURCE_DIR"
           (string-append (getenv "HOME") "/repos/guix")))
(define output-dir
  (string-append workdir "/0000000000000000-which-" which-version))
(define source-tarball
  (string-append workdir "/which-" which-version ".tar.gz"))
(define source-dir
  (string-append workdir "/which-" which-version))
(define metadata-file
  (string-append workdir "/gnu-which-guix-phase-runner-metadata.txt"))
(define expected-sha256-hex
  (nix-base32->hex expected-nix-base32))
(define selected-phase-names
  '(set-SOURCE-DATE-EPOCH unpack configure build check install))
(define selected-phases
  (phase-subset selected-phase-names))
(define run-path "/bin:/usr/bin")
(define expected-which-output "/bin/sh")

(setenv "NIX_BUILD_TOP" workdir)
(mkdir-p workdir)

(format #t "Using workdir: ~a~%" workdir)
(format #t "Using Guix source: ~a~%" guix-source-dir)
(format #t "Fetching source: ~a~%" source-url)
(invoke "fetch" "-o" source-tarball source-url)

(let ((actual-sha256-hex (command-output "sha256" "-q" source-tarball)))
  (unless (string=? actual-sha256-hex expected-sha256-hex)
    (error (format #f "sha256 mismatch: expected ~a but got ~a"
                   expected-sha256-hex actual-sha256-hex)))

  (format #t "Verified SHA256: ~a~%" actual-sha256-hex)
  (format #t "Running Guix builder phases: ~s~%" selected-phase-names)

  (with-directory-excursion workdir
    (gnu-build #:source source-tarball
               #:outputs `(("out" . ,output-dir))
               #:phases selected-phases
               #:tests? #t))

  (let* ((installed-binary (string-append output-dir "/bin/which"))
         (which-output (with-path run-path
                         (lambda ()
                           (command-output installed-binary "sh"))))
         (host-triplet (host-triplet-from-source source-dir))
         (binary-file (command-output "file" installed-binary))
         (runtime-deps (command-output "ldd" installed-binary))
         (check-summary (maybe-read-test-log source-dir))
         (guile-bin (or (getenv "GUILE_BIN") "<unset>"))
         (uname-string (command-output "uname" "-a")))
    (unless (string=? which-output expected-which-output)
      (error (format #f "unexpected which output: ~s" which-output)))

    (call-with-output-file metadata-file
      (lambda (port)
        (format port "which_version=~a~%" which-version)
        (format port "source_url=~a~%" source-url)
        (format port "expected_nix_base32=~a~%" expected-nix-base32)
        (format port "expected_sha256_hex=~a~%" expected-sha256-hex)
        (format port "actual_sha256_hex=~a~%" actual-sha256-hex)
        (format port "guix_source_dir=~a~%" guix-source-dir)
        (format port "guile_bin=~a~%" guile-bin)
        (format port "workdir=~a~%" workdir)
        (format port "source_tarball=~a~%" source-tarball)
        (format port "source_dir=~a~%" source-dir)
        (format port "output_dir=~a~%" output-dir)
        (format port "installed_binary=~a~%" installed-binary)
        (format port "run_path=~a~%" run-path)
        (format port "which_output=~a~%" which-output)
        (format port "expected_which_output=~a~%" expected-which-output)
        (format port "host_triplet=~a~%" host-triplet)
        (format port "selected_phases=~s~%" selected-phase-names)
        (format port "check_phase=passed~%")
        (format port "binary_file=~a~%" binary-file)
        (format port "uname=~a~%" uname-string)
        (format port "check_summary_begin~%~a~%check_summary_end~%"
                check-summary)
        (format port "runtime_deps_begin~%~a~%runtime_deps_end~%"
                runtime-deps)))

    (when (getenv "METADATA_OUT")
      (mkdir-p (dirname (getenv "METADATA_OUT")))
      (copy-file metadata-file (getenv "METADATA_OUT")))

    (format #t "PASS gnu-which-guix-phase-runner~%")
    (format #t "Which output: ~a~%" which-output)
    (format #t "Installed binary: ~a~%" installed-binary)
    (format #t "Metadata file: ~a~%" metadata-file)
    (when (getenv "METADATA_OUT")
      (format #t "Copied metadata to: ~a~%" (getenv "METADATA_OUT")))
    (display "--- metadata ---\n")
    (display (call-with-input-file metadata-file get-string-all))))