import os

fn main() {
    if os.args.len <= 1 {
        eprintln('please specify a C++ compiler')
        exit(1)
    }
    cc := os.args[1]
    if os.execute('${os.quoted_path(cc)} -v').exit_code != 0 {
        eprintln('please specify a valid C++ compiler')
        exit(1)
    }
    cc_type, cc_version, cc_os := get_cc_info(cc)
    triple := '${cc_type}-${cc_version}-${cc_os}'
    println('compiler: ${triple}')

    search_paths := get_search_paths(cc)
    atomic_path := find_file(search_paths, 'atomic') or {
        eprintln(err)
        exit(2)
    }

    bitsatomicbase_path := find_file(search_paths, 'bits/atomic_base.h') or {
        if cc_os == 'linux' {
            eprintln(err)
            exit(2)
        }
        'no_file' // bits/atomic_base.h is only used on linux
    }

    patch_atomic(os.join_path(os.dir(@FILE), 'atomic.h'), atomic_path) or {
        eprintln(err)
        exit(2)
    }

    if bitsatomicbase_path != 'no_file' {
        patch_bitsatomicbase(os.join_path(os.dir(@FILE), 'bitsatomicbase.h'), bitsatomicbase_path) or {
            eprintln(err)
            exit(2)
        }
    }

    println('${atomic_path}:::${bitsatomicbase_path}')
}

fn get_cc_info(cc string) (string, string, string) {
    cc_type := if cc.contains('clang') {
        'clang'
    } else if cc.contains('g') {
        'gcc'
    } else {
        eprintln('only gcc and clang are supported')
        exit(1)
        'none'
    }

    lines := os.execute('${os.quoted_path(cc)} -v').output.split('\n')

    // gcc and clang both have the same way way to say what version they have and what the host target triple is
    cc_version :=
        lines.filter(it.contains('${cc_type} version '))[0].all_after('${cc_type} version ').all_before('.')

    cc_os := lines.filter(it.starts_with('Target: '))[0].all_after('Target: ').split('-')[2]

    return cc_type, cc_version, if cc_os.contains('darwin') {
        'darwin' // remove 20.6.0 from darwin20.6.0
    } else {
        cc_os
    }
}

fn get_search_paths(cc string) []string {
    result := os.execute('${os.quoted_path(cc)} -v -x c++ /dev/null').output
    lines := result.split('\n')
    search_path := lines[lines.index('#include <...> search starts here:') + 1..lines.index('End of search list.')]
    return search_path.map(os.real_path(it.all_before('(').trim_space()))
}

fn find_file(search_paths []string, file string) !string {
    for search_path in search_paths {
        if os.exists(os.join_path(search_path, file)) {
            return os.join_path(search_path, file)
        }
    }
    return error('${file} not found')
}

fn patch_atomic(outfile string, infile string) ! {
    lines := os.read_file(infile)!.split('\n')
    outlines := lines.filter(!it.contains('atomic(const atomic&) = delete;'))
    outtext := outlines.join('\n').replace('#include <bits/atomic_base.h>',
        '#include "bitsatomicbase.h"')
    os.write_file(outfile, outtext)!
}

fn patch_bitsatomicbase(outfile string, infile string) ! {
    lines := os.read_file(infile)!.split('\n')
    outlines := lines.filter(!it.contains('__atomic_base(const __atomic_base&) = delete;'))
    outtext := outlines.join('\n').replace('#include <bits/atomic_base.h>',
        '#include "bitsatomicbase.h"')
    os.write_file(outfile, outtext)!
}