@echo off
REM Merge multiple compilation command files generated by clang -MJ and dump it
REM to standard output as a JSON array.
REM
REM An entry generated by clang -MJ, looks like this:
REM
REM {
REM   "directory": "/home/user/dev/llvm/build",
REM   "file": "/tmp/foo.cpp",
REM   "output": "foo.o",
REM   "arguments": ["/usr/bin/clang-5.0", "-xc++", "/tmp/foo.cpp", "--driver-mode=g++", "-Wall", "-I", "/home/user/dev/libcpp/libcpp/include", "-c", "--target=x86_64-unknown-linux-gnu"]
REM }
REM
REM See: https://sarcasm.github.io/notes/dev/compilation-database.html#clang

setlocal EnableDelayedExpansion
if [%1]==[] (
    echo Usage: %0 [compilation command files...]
    exit /b -1
)

REM Count the number of arguments we received
set arg_count=0
for %%x in (%*) do ( set /A arg_count+=1 )

REM Open a JSON array to splat the JSON compile commands objects into
echo [

REM Append the compile commands in
set arg_next_index=0
for %%x in (%*) do (
    set /A arg_next_index+=1
    set /P contents=<%%x

    REM On the last compile command to append to the array, remove the trailing
    REM comma on the JSON object
    if !arg_next_index! == !arg_count! (
        set contents=!contents:~0,-1!
    )

    echo !contents!
)

REM Close the JSON array
echo ]