#!/bin/bash -e
# Examples:
#   # Show diff between the TABLES in two databases
#   TABLES="languages" diff-mysql database1 database2
#
#   # Show diff between languages TABLES skipping any output containing 'python'
#   FILTER_CMD='grep -v python' TABLES=languages diff-mysql database{1,2}
#
#   # Filter at the database level instead
#   FILTER_SQL="WHERE languages.name = 'python'" TABLES=languages diff-mysql database{1,2}
#
set -eo pipefail

DB_USERNAME=${DB_USERNAME:-root}
DB_PASSWORD=${DB_PASSWORD:-password}
DB_HOST=${DB_HOST:-localhost}

MAX_ROW_COUNT=${MAX_ROW_COUNT:-100}
SKIP=${SKIP:-messages}

DB_NAME1=$1
DB_NAME2=$2

puts() { local color=$1; local prefix=$2; local msg=$3
  echo -e "[$(date +%Y%m%d%H%M%S)] [${color};1m${prefix}:[${color}m $msg" 1>&2
}

info()    { local msg=$*; puts 34 INFO "$msg"   ; }
success() { local msg=$*; puts 32 SUCCESS "$msg"; }
error()   { local msg=$*; puts 31 ERROR "$msg"  ; }

skip() { local name=$1
  for skip_name in $SKIP; do
    [ "$skip_name" == "$name" ] && return 0
  done
  return 1
}

do_mysql() { local db_name="$1"; shift
  mysql "$@" --user="$DB_USERNAME" --password="$DB_PASSWORD" --host="$DB_HOST" "$db_name" 2> /dev/null
}

do_mysql_silent() { local db_name=$1
  do_mysql "$db_name" --silent
}

tables() { local db_name=$1
  info "Fetching table names from database $db_name (host '$DB_HOST') ..."
  echo "show tables" |
  do_mysql_silent "$db_name"
}
TABLES=${TABLES:-$(tables "$DB_NAME1")}

count_rows() { local table=$1; local db_name=$2
  echo "select count(id) from $table" |
  do_mysql_silent "$db_name"
}

diff_cmd() {
  #diff -u $@
  COLOR_ENABLED=1 ${DIFF_CMD:-diff-csv} "$@"
}

filter_cmd() {
  ${FILTER_CMD:-cat}
}

dump_table() { local table=$1; local db_name=$2
  echo "$(echo 'SELECT *') FROM $table ${FILTER_SQL}" |
  do_mysql "$db_name" |
  filter_cmd
}

table_diff() { local table="$1"
  info "Diffing $table ($DB_NAME1 vs $DB_NAME2)"
  diff_cmd <(dump_table "$table" {"$DB_NAME1","$DB_NAME2"})
}


exit_code=0
for table in $TABLES; do
  row_count=$(count_rows "$table" "$DB_NAME1")
  if [ $row_count -lt $MAX_ROW_COUNT ]; then
    if skip "$table"; then
      info "Skipping $table (as it was referenced in SKIP)"
    else
      table_diff "$table" || exit_code=$?
    fi
  else
    info "Skipping $table (as row count exceeds MAX_ROW_COUNT, $row_count > $MAX_ROW_COUNT)"
  fi
done
exit $exit_code