#!/bin/bash

# Development script: bisect a git repository to find the first broken commit
# since the last known good version.

# If any of the pipe segments fail, treat that as a fail.

set -o pipefail

if test $Argc -lt 4
{
  echo "usage: bisectinate ARCH PACKAGE REPO[@BAD] GOOD [TEST...]" > !2
  echo > !2
  echo "Bisect PACKAGE for ARCH, from START to BAD within REPO" > !2
  exit 1
}

# Parse command line options

global ARCH := $1
global PKG := $2
global REPO := $(3/@*/)
global BRANCH := $(3/*@/)
test $BRANCH == $3 && global BRANCH := 'master'
global START := $4
shift 4
global TEST := $1

global TOP := $[pwd]
test -z $SRCDIR && global SRCDIR := ""$TOP/packages""
test -z $BUILD && global BUILD := ""$TOP/build""

if test ! -d "$REPO/.git"
{
  echo "No git repo at $REPO"
  exit 1
}

test -z $TEST && global TEST := 'true'

# For kernel and busybox bisects, only redo part of the build

if test $PKG == linux && test -e "$BUILD/root-filesystem-$ARCH".tar.bz2
{
  global ZAPJUST := 'linux-kernel'
} elif test $PKG == busybox &&
     test -e "$BUILD/simple-cross-compiler-$ARCH.tar.bz2"
{
  global ZAPJUST := 'root-filesystem'
} else {
  global ZAPJUST := ''
}

# Initialize bisection repository

rm -rf "$BUILD/packages/alt-$PKG" "$SRCDIR/alt-$PKG-0.tar.bz2" &&
mkdir -p "$BUILD"/{logs,packages} &&
cd "$BUILD/packages" &&
git clone $REPO "alt-$PKG" &&
cd "alt-$PKG" &&
git bisect start &&
git bisect good $START || exit 1

global RESULT := ""bad $BRANCH""

# Loop through bisection results

while true
{
  # Bisect repository to prepare next version to build.  Exit if done.

  cd "$BUILD/packages/alt-$PKG" &&
  git clean -fdx &&
  git checkout -f || exit 1

  global RESULT := $[git bisect $RESULT]
  echo $RESULT
  test ! $[echo $RESULT | head -n 1 | grep "^Bisecting:] && exit

  # Update log

  git show > "$BUILD/logs/bisectinate-$(ARCH).txt"
  git bisect log > "$BUILD/logs/bisectinate-$(ARCH).log"
  # The "cat" bypasses git's stupid overengineered built-in call to less.
  git log HEAD -1 | cat
  echo "Testing..."

  cd $TOP || exit 1

  # Figure out how much ./build.sh needs to rebuild

  test ! -z $ZAPJUST &&
    rm -rf "$BUILD/$(ZAPJUST)-$ARCH"{,.tar.bz2} ||
    rm -rf "$BUILD"/*-"$ARCH"{,.tar.bz2}

  # Try the build

  env EXTRACT_ALL=1 ALLOW_PATCH_FAILURE=1 USE_ALT=$PKG \
    ./build.sh $ARCH !2 > !1 | tee -a "$BUILD"/logs/bisectinate-"$ARCH".txt

  # Did it work?

  global RESULT := 'bad'
  if test -e "$BUILD"/system-image-"$ARCH".tar.bz2
  {
    set -o pipefail
    env ARCH=$ARCH more/timeout.sh 60 $TEST !2 > !1 | \
      tee -a "$BUILD/logs/bisectinate-$ARCH".txt
    test $Status -eq 0 && global RESULT := 'good'
  }

  # Keep the last "good" and "bad" logs, separately.

  mv "$BUILD"/logs/bisectinate{,-$RESULT}-"$ARCH".txt
}