#!/usr/bin/env bash

set -eu

## Functions/
usage() {
cat << EOF
SYNOPSIS

    gpm leverages the power of the go get command and the underlying version
    control systems used by it to set your Go dependencies to desired versions,
    thus allowing easily reproducible builds in your Go projects.

    A Godeps file in the root of your Go application is expected containing
    the import paths of your packages and a specific tag or commit hash
    from its version control system, an example Godeps file looks like this:

    $ cat Godeps
    # This is a comment
    github.com/nu7hatch/gotrail         v0.0.2
    github.com/replicon/fast-archiver   v1.02   #This is another comment!
    github.com/nu7hatch/gotrail         2eb79d1f03ab24bacbc32b15b75769880629a865
    # pull in gopkg.in/mgo.v2 from an alternate location
    gopkg.in/mgo.v2                     c9fd3712fbf3e92924c974dce16da2d322508fe2          github.com/go-mgo/mgo

    gpm has a companion tool, called [gvp](https://github.com/pote/gvp) which
    provides vendoring functionalities, it alters your GOPATH so every project
    has its own isolated dependency directory, its usage is recommended.

USAGE
      $ gpm             # Same as 'install'.
      $ gpm install     # Parses the Godeps file, installs dependencies and sets
                        # them to the appropriate version.
      $ gpm version     # Outputs version information
      $ gpm help        # Prints this message
EOF
}

# Iterates over Godep file dependencies and sets
# the specified version on each of them.
set_dependencies() {
  local pids=()
  while read line; do
    local line=`echo $line | sed 's/#.*//;/^\s*$/d' || echo ""`
    [ ! "$line" ] && continue
    (
      line=($line)
      local package=${line[0]}
      local version=${line[1]}
      local dest=""
      if [[ -n ${line[2]:-} ]]; then
        dest=$package
        package=${line[2]}
      fi

      if [[ "$OSTYPE" == "cygwin" || "$OSTYPE" == "msys" ]]
      then
        local install_path="${GOPATH%%;*}/src/${package%%/...}"
      else
        local install_path="${GOPATH%%:*}/src/${package%%/...}"
      fi

      [[ -e "$install_path/.git/index.lock" ||
         -e "$install_path/.hg/store/lock"  ||
         -e "$install_path/.bzr/checkout/lock" ]] && wait

      echo ">> Getting package "$package""
      go get -u -d "$package"

      cd $install_path
      hg update     "$version" > /dev/null 2>&1 || \
      git checkout  "$version" > /dev/null 2>&1 || \
      bzr revert -r "$version" > /dev/null 2>&1 || \
      #svn has exit status of 0 when there is no .svn
      { [ -d .svn ] && svn update -r "$version" > /dev/null 2>&1; } || \
      { echo ">> Failed to set $package to version $version"; exit 1; }

      echo ">> Set $package to version $version"
      if [[ -n "$dest" ]] ; then
        if [[ "$OSTYPE" == "cygwin" || "$OSTYPE" == "msys" ]]
        then
          local dest_path="${GOPATH%%;*}/src/${dest%%/...}"
        else
          local dest_path="${GOPATH%%:*}/src/${dest%%/...}"
        fi
        mkdir -p "$(dirname "$dest_path")"
        cd "$(dirname "$dest_path")"
        rm -rf $dest_path
        mv $install_path $dest_path
        echo ">> moved $install_path to $dest_path"
      fi
    ) &
    pids=(${pids[@]-} $!)
  done < $1

  for pid in "${pids[@]-}"; do
      wait $pid
      local status=$?
      [ $status -ne 0 ] && exit $status
  done

  echo ">> All Done"
}
## /Functions

## Command Line Parsing
case "${1:-"install"}" in
  "version")
    echo ">> gpm v1.2.1"
    ;;
  "install")
    deps_file="${2:-"Godeps"}"
    [[ -f "$deps_file" ]] || (echo ">> $deps_file file does not exist." && exit 1)
    (go version > /dev/null) ||
      ( echo ">> Go is currently not installed or in your PATH" && exit 1)
    set_dependencies $deps_file
    ;;
  "help")
    usage
    ;;
  *)
    ## Support for Plugins: if command is unknown search for a gpm-command executable.
    if command -v "gpm-$1" > /dev/null
    then
      plugin=$1 &&
      shift     &&
      gpm-$plugin $@ &&
      exit
    else
      usage && exit 1
    fi
    ;;
esac