[has_globals]
module builtin

type FnExitCb = fn ()

fn C.atexit(f FnExitCb) int
fn C.strerror(int) &char

[noreturn]
fn vhalt() {
    for {}
}

[markused]
fn v_segmentation_fault_handler(signal_number int) {
    $if freestanding {
        eprintln('signal 11: segmentation fault')
    } $else {
        C.fprintf(C.stderr, c'signal %d: segmentation fault\n', signal_number)
    }
    $if use_libbacktrace ? {
        eprint_libbacktrace(1)
    } $else {
        print_backtrace()
    }
    exit(128 + signal_number)
}

// exit terminates execution immediately and returns exit `code` to the shell.
[noreturn]
pub fn exit(code int) {
    C.exit(code)
}

fn vcommithash() string {
    return unsafe { tos5(&char(C.V_CURRENT_COMMIT_HASH)) }
}

// panic_debug private function that V uses for panics, -cg/-g is passed
// recent versions of tcc print nicer backtraces automatically
// Note: the duplication here is because tcc_backtrace should be called directly
// inside the panic functions.
[noreturn]
fn panic_debug(line_no int, file string, mod string, fn_name string, s string) {
    // Note: the order here is important for a stabler test output
    // module is less likely to change than function, etc...
    // During edits, the line number will change most frequently,
    // so it is last
    $if freestanding {
        bare_panic(s)
    } $else {
        eprintln('================ V panic ================')
        eprintln('   module: ${mod}')
        eprintln(' function: ${fn_name}()')
        eprintln('  message: ${s}')
        eprintln('     file: ${file}:${line_no}')
        eprintln('   v hash: ${vcommithash()}')
        eprintln('=========================================')
        $if exit_after_panic_message ? {
            C.exit(1)
        } $else $if no_backtrace ? {
            C.exit(1)
        } $else {
            $if tinyc {
                $if panics_break_into_debugger ? {
                    break_if_debugger_attached()
                } $else {
                    C.tcc_backtrace(c'Backtrace')
                }
                C.exit(1)
            }
            $if use_libbacktrace ? {
                eprint_libbacktrace(1)
            } $else {
                print_backtrace_skipping_top_frames(1)
            }
            $if panics_break_into_debugger ? {
                break_if_debugger_attached()
            }
            C.exit(1)
        }
    }
    vhalt()
}

// panic_option_not_set is called by V, when you use option error propagation in your main function.
// It ends the program with a panic.
[noreturn]
pub fn panic_option_not_set(s string) {
    panic('option not set (${s})')
}

// panic_result_not_set is called by V, when you use result error propagation in your main function
// It ends the program with a panic.
[noreturn]
pub fn panic_result_not_set(s string) {
    panic('result not set (${s})')
}

// panic prints a nice error message, then exits the process with exit code of 1.
// It also shows a backtrace on most platforms.
[noreturn]
pub fn panic(s string) {
    $if freestanding {
        bare_panic(s)
    } $else {
        eprint('V panic: ')
        eprintln(s)
        eprintln('v hash: ${vcommithash()}')
        $if exit_after_panic_message ? {
            C.exit(1)
        } $else $if no_backtrace ? {
            C.exit(1)
        } $else {
            $if tinyc {
                $if panics_break_into_debugger ? {
                    break_if_debugger_attached()
                } $else {
                    C.tcc_backtrace(c'Backtrace')
                }
                C.exit(1)
            }
            $if use_libbacktrace ? {
                eprint_libbacktrace(1)
            } $else {
                print_backtrace_skipping_top_frames(1)
            }
            $if panics_break_into_debugger ? {
                break_if_debugger_attached()
            }
            C.exit(1)
        }
    }
    vhalt()
}

// return a C-API error message matching to `errnum`
pub fn c_error_number_str(errnum int) string {
    mut err_msg := ''
    $if freestanding {
        err_msg = 'error ${errnum}'
    } $else {
        $if !vinix {
            c_msg := C.strerror(errnum)
            err_msg = string{
                str: &u8(c_msg)
                len: unsafe { C.strlen(c_msg) }
                is_lit: 1
            }
        }
    }
    return err_msg
}

// panic with a C-API error message matching `errnum`
[noreturn]
pub fn panic_error_number(basestr string, errnum int) {
    panic(basestr + c_error_number_str(errnum))
}

// eprintln prints a message with a line end, to stderr. Both stderr and stdout are flushed.
pub fn eprintln(s string) {
    if s.str == 0 {
        eprintln('eprintln(NIL)')
        return
    }
    $if freestanding {
        // flushing is only a thing with C.FILE from stdio.h, not on the syscall level
        bare_eprint(s.str, u64(s.len))
        bare_eprint(c'\n', 1)
    } $else $if ios {
        C.WrappedNSLog(s.str)
    } $else {
        C.fflush(C.stdout)
        C.fflush(C.stderr)
        // eprintln is used in panics, so it should not fail at all
        $if android && !termux {
            C.android_print(C.stderr, c'%.*s\n', s.len, s.str)
        }
        _writeln_to_fd(2, s)
        C.fflush(C.stderr)
    }
}

// eprint prints a message to stderr. Both stderr and stdout are flushed.
pub fn eprint(s string) {
    if s.str == 0 {
        eprint('eprint(NIL)')
        return
    }
    $if freestanding {
        // flushing is only a thing with C.FILE from stdio.h, not on the syscall level
        bare_eprint(s.str, u64(s.len))
    } $else $if ios {
        // TODO: Implement a buffer as NSLog doesn't have a "print"
        C.WrappedNSLog(s.str)
    } $else {
        C.fflush(C.stdout)
        C.fflush(C.stderr)
        $if android && !termux {
            C.android_print(C.stderr, c'%.*s', s.len, s.str)
        }
        _write_buf_to_fd(2, s.str, s.len)
        C.fflush(C.stderr)
    }
}

pub fn flush_stdout() {
    $if freestanding {
        not_implemented := 'flush_stdout is not implemented\n'
        bare_eprint(not_implemented.str, u64(not_implemented.len))
    } $else {
        C.fflush(C.stdout)
    }
}

pub fn flush_stderr() {
    $if freestanding {
        not_implemented := 'flush_stderr is not implemented\n'
        bare_eprint(not_implemented.str, u64(not_implemented.len))
    } $else {
        C.fflush(C.stderr)
    }
}

// print prints a message to stdout. Note that unlike `eprint`, stdout is not automatically flushed.
[manualfree]
pub fn print(s string) {
    $if android && !termux {
        C.android_print(C.stdout, c'%.*s\n', s.len, s.str)
    } $else $if ios {
        // TODO: Implement a buffer as NSLog doesn't have a "print"
        C.WrappedNSLog(s.str)
    } $else $if freestanding {
        bare_print(s.str, u64(s.len))
    } $else {
        _write_buf_to_fd(1, s.str, s.len)
    }
}

// println prints a message with a line end, to stdout. Note that unlike `eprintln`, stdout is not automatically flushed.
[manualfree]
pub fn println(s string) {
    if s.str == 0 {
        println('println(NIL)')
        return
    }
    $if android && !termux {
        C.android_print(C.stdout, c'%.*s\n', s.len, s.str)
        return
    } $else $if ios {
        C.WrappedNSLog(s.str)
        return
    } $else $if freestanding {
        bare_print(s.str, u64(s.len))
        bare_print(c'\n', 1)
        return
    } $else {
        _writeln_to_fd(1, s)
    }
}

[manualfree]
fn _writeln_to_fd(fd int, s string) {
    $if !bultin_writeln_should_write_at_once ? {
        lf := u8(`\n`)
        _write_buf_to_fd(fd, s.str, s.len)
        _write_buf_to_fd(fd, &lf, 1)
        return
    }
    unsafe {
        buf_len := s.len + 1 // space for \n
        mut buf := malloc(buf_len)
        defer {
            free(buf)
        }
        C.memcpy(buf, s.str, s.len)
        buf[s.len] = `\n`
        _write_buf_to_fd(fd, buf, buf_len)
    }
}

[manualfree]
fn _write_buf_to_fd(fd int, buf &u8, buf_len int) {
    if buf_len <= 0 {
        return
    }
    mut ptr := unsafe { buf }
    mut remaining_bytes := isize(buf_len)
    mut x := isize(0)
    $if freestanding || vinix || bultin_write_buf_to_fd_should_use_c_write ? {
        unsafe {
            for remaining_bytes > 0 {
                x = C.write(fd, ptr, remaining_bytes)
                ptr += x
                remaining_bytes -= x
            }
        }
    } $else {
        mut stream := voidptr(C.stdout)
        if fd == 2 {
            stream = voidptr(C.stderr)
        }
        unsafe {
            for remaining_bytes > 0 {
                x = isize(C.fwrite(ptr, 1, remaining_bytes, stream))
                ptr += x
                remaining_bytes -= x
            }
        }
    }
}

__global total_m = i64(0)
// malloc dynamically allocates a `n` bytes block of memory on the heap.
// malloc returns a `byteptr` pointing to the memory address of the allocated space.
// unlike the `calloc` family of functions - malloc will not zero the memory block.
[unsafe]
pub fn malloc(n isize) &u8 {
    $if trace_malloc ? {
        total_m += n
        C.fprintf(C.stderr, c'_v_malloc %6d total %10d\n', n, total_m)
        // print_backtrace()
    }
    if n < 0 {
        panic('malloc(${n} < 0)')
    }
    $if vplayground ? {
        if n > 10000 {
            panic('allocating more than 10 KB at once is not allowed in the V playground')
        }
        if total_m > 50 * 1024 * 1024 {
            panic('allocating more than 50 MB is not allowed in the V playground')
        }
    }
    mut res := &u8(0)
    $if prealloc {
        return unsafe { prealloc_malloc(n) }
    } $else $if gcboehm ? {
        unsafe {
            res = C.GC_MALLOC(n)
        }
    } $else $if freestanding {
        // todo: is this safe to call malloc there? We export __malloc as malloc and it uses dlmalloc behind the scenes
        // so theoretically it is safe
        res = unsafe { __malloc(usize(n)) }
    } $else {
        res = unsafe { C.malloc(n) }
    }
    if res == 0 {
        panic('malloc(${n}) failed')
    }
    $if debug_malloc ? {
        // Fill in the memory with something != 0 i.e. `M`, so it is easier to spot
        // when the calling code wrongly relies on it being zeroed.
        unsafe { C.memset(res, 0x4D, n) }
    }
    return res
}

[unsafe]
pub fn malloc_noscan(n isize) &u8 {
    $if trace_malloc ? {
        total_m += n
        C.fprintf(C.stderr, c'malloc_noscan %6d total %10d\n', n, total_m)
        // print_backtrace()
    }
    if n < 0 {
        panic('malloc_noscan(${n} < 0)')
    }
    $if vplayground ? {
        if n > 10000 {
            panic('allocating more than 10 KB at once is not allowed in the V playground')
        }
        if total_m > 50 * 1024 * 1024 {
            panic('allocating more than 50 MB is not allowed in the V playground')
        }
    }
    mut res := &u8(0)
    $if prealloc {
        return unsafe { prealloc_malloc(n) }
    } $else $if gcboehm ? {
        $if gcboehm_opt ? {
            unsafe {
                res = C.GC_MALLOC_ATOMIC(n)
            }
        } $else {
            unsafe {
                res = C.GC_MALLOC(n)
            }
        }
    } $else $if freestanding {
        res = unsafe { __malloc(usize(n)) }
    } $else {
        res = unsafe { C.malloc(n) }
    }
    if res == 0 {
        panic('malloc_noscan(${n}) failed')
    }
    $if debug_malloc ? {
        // Fill in the memory with something != 0 i.e. `M`, so it is easier to spot
        // when the calling code wrongly relies on it being zeroed.
        unsafe { C.memset(res, 0x4D, n) }
    }
    return res
}

[inline]
fn __at_least_one(how_many u64) u64 {
    // handle the case for allocating memory for empty structs, which have sizeof(EmptyStruct) == 0
    // in this case, just allocate a single byte, avoiding the panic for malloc(0)
    if how_many == 0 {
        return 1
    }
    return how_many
}

// malloc_uncollectable dynamically allocates a `n` bytes block of memory
// on the heap, which will NOT be garbage-collected (but its contents will).
[unsafe]
pub fn malloc_uncollectable(n isize) &u8 {
    $if trace_malloc ? {
        total_m += n
        C.fprintf(C.stderr, c'malloc_uncollectable %6d total %10d\n', n, total_m)
        // print_backtrace()
    }
    if n < 0 {
        panic('malloc_uncollectable(${n} < 0)')
    }
    $if vplayground ? {
        if n > 10000 {
            panic('allocating more than 10 KB at once is not allowed in the V playground')
        }
        if total_m > 50 * 1024 * 1024 {
            panic('allocating more than 50 MB is not allowed in the V playground')
        }
    }
    mut res := &u8(0)
    $if prealloc {
        return unsafe { prealloc_malloc(n) }
    } $else $if gcboehm ? {
        unsafe {
            res = C.GC_MALLOC_UNCOLLECTABLE(n)
        }
    } $else $if freestanding {
        res = unsafe { __malloc(usize(n)) }
    } $else {
        res = unsafe { C.malloc(n) }
    }
    if res == 0 {
        panic('malloc_uncollectable(${n}) failed')
    }
    $if debug_malloc ? {
        // Fill in the memory with something != 0 i.e. `M`, so it is easier to spot
        // when the calling code wrongly relies on it being zeroed.
        unsafe { C.memset(res, 0x4D, n) }
    }
    return res
}

// v_realloc resizes the memory block `b` with `n` bytes.
// The `b byteptr` must be a pointer to an existing memory block
// previously allocated with `malloc`, `v_calloc` or `vcalloc`.
// Please, see also realloc_data, and use it instead if possible.
[unsafe]
pub fn v_realloc(b &u8, n isize) &u8 {
    $if trace_realloc ? {
        C.fprintf(C.stderr, c'v_realloc %6d\n', n)
    }
    mut new_ptr := &u8(0)
    $if prealloc {
        unsafe {
            new_ptr = malloc(n)
            C.memcpy(new_ptr, b, n)
        }
        return new_ptr
    } $else $if gcboehm ? {
        new_ptr = unsafe { C.GC_REALLOC(b, n) }
    } $else {
        new_ptr = unsafe { C.realloc(b, n) }
    }
    if new_ptr == 0 {
        panic('realloc(${n}) failed')
    }
    return new_ptr
}

// realloc_data resizes the memory block pointed by `old_data` to `new_size`
// bytes. `old_data` must be a pointer to an existing memory block, previously
// allocated with `malloc`, `v_calloc` or `vcalloc`, of size `old_data`.
// realloc_data returns a pointer to the new location of the block.
// Note: if you know the old data size, it is preferable to call `realloc_data`,
// instead of `v_realloc`, at least during development, because `realloc_data`
// can make debugging easier, when you compile your program with
// `-d debug_realloc`.
[unsafe]
pub fn realloc_data(old_data &u8, old_size int, new_size int) &u8 {
    $if trace_realloc ? {
        C.fprintf(C.stderr, c'realloc_data old_size: %6d new_size: %6d\n', old_size, new_size)
    }
    $if prealloc {
        return unsafe { prealloc_realloc(old_data, old_size, new_size) }
    }
    $if debug_realloc ? {
        // Note: this is slower, but helps debugging memory problems.
        // The main idea is to always force reallocating:
        // 1) allocate a new memory block
        // 2) copy the old to the new
        // 3) fill the old with 0x57 (`W`)
        // 4) free the old block
        // => if there is still a pointer to the old block somewhere
        //    it will point to memory that is now filled with 0x57.
        unsafe {
            new_ptr := malloc(new_size)
            min_size := if old_size < new_size { old_size } else { new_size }
            C.memcpy(new_ptr, old_data, min_size)
            C.memset(old_data, 0x57, old_size)
            free(old_data)
            return new_ptr
        }
    }
    mut nptr := &u8(0)
    $if gcboehm ? {
        nptr = unsafe { C.GC_REALLOC(old_data, new_size) }
    } $else {
        nptr = unsafe { C.realloc(old_data, new_size) }
    }
    if nptr == 0 {
        panic('realloc_data(${old_data}, ${old_size}, ${new_size}) failed')
    }
    return nptr
}

// vcalloc dynamically allocates a zeroed `n` bytes block of memory on the heap.
// vcalloc returns a `byteptr` pointing to the memory address of the allocated space.
// Unlike `v_calloc` vcalloc checks for negative values given in `n`.
pub fn vcalloc(n isize) &u8 {
    $if trace_vcalloc ? {
        total_m += n
        C.fprintf(C.stderr, c'vcalloc %6d total %10d\n', n, total_m)
    }
    if n < 0 {
        panic('calloc(${n} < 0)')
    } else if n == 0 {
        return &u8(0)
    }
    $if prealloc {
        return unsafe { prealloc_calloc(n) }
    } $else $if gcboehm ? {
        return unsafe { &u8(C.GC_MALLOC(n)) }
    } $else {
        return unsafe { C.calloc(1, n) }
    }
}

// special versions of the above that allocate memory which is not scanned
// for pointers (but is collected) when the Boehm garbage collection is used
pub fn vcalloc_noscan(n isize) &u8 {
    $if trace_vcalloc ? {
        total_m += n
        C.fprintf(C.stderr, c'vcalloc_noscan %6d total %10d\n', n, total_m)
    }
    $if prealloc {
        return unsafe { prealloc_calloc(n) }
    } $else $if gcboehm ? {
        $if vplayground ? {
            if n > 10000 {
                panic('allocating more than 10 KB is not allowed in the playground')
            }
        }
        if n < 0 {
            panic('calloc_noscan(${n} < 0)')
        }
        return $if gcboehm_opt ? {
            unsafe { &u8(C.memset(C.GC_MALLOC_ATOMIC(n), 0, n)) }
        } $else {
            unsafe { &u8(C.GC_MALLOC(n)) }
        }
    } $else {
        return unsafe { vcalloc(n) }
    }
}

// free allows for manually freeing memory allocated at the address `ptr`.
[unsafe]
pub fn free(ptr voidptr) {
    $if prealloc {
        return
    } $else $if gcboehm ? {
        // It is generally better to leave it to Boehm's gc to free things.
        // Calling C.GC_FREE(ptr) was tried initially, but does not work
        // well with programs that do manual management themselves.
        //
        // The exception is doing leak detection for manual memory management:
        $if gcboehm_leak ? {
            unsafe { C.GC_FREE(ptr) }
        }
    } $else {
        C.free(ptr)
    }
}

// memdup dynamically allocates a `sz` bytes block of memory on the heap
// memdup then copies the contents of `src` into the allocated space and
// returns a pointer to the newly allocated space.
[unsafe]
pub fn memdup(src voidptr, sz int) voidptr {
    $if trace_memdup ? {
        C.fprintf(C.stderr, c'memdup size: %10d\n', sz)
    }
    if sz == 0 {
        return vcalloc(1)
    }
    unsafe {
        mem := malloc(sz)
        return C.memcpy(mem, src, sz)
    }
}

[unsafe]
pub fn memdup_noscan(src voidptr, sz int) voidptr {
    $if trace_memdup ? {
        C.fprintf(C.stderr, c'memdup_noscan size: %10d\n', sz)
    }
    if sz == 0 {
        return vcalloc_noscan(1)
    }
    unsafe {
        mem := malloc_noscan(sz)
        return C.memcpy(mem, src, sz)
    }
}

// memdup_uncollectable dynamically allocates a `sz` bytes block of memory
// on the heap, which will NOT be garbage-collected (but its contents will).
// memdup_uncollectable then copies the contents of `src` into the allocated
// space and returns a pointer to the newly allocated space.
[unsafe]
pub fn memdup_uncollectable(src voidptr, sz int) voidptr {
    $if trace_memdup ? {
        C.fprintf(C.stderr, c'memdup_uncollectable size: %10d\n', sz)
    }
    if sz == 0 {
        return vcalloc(1)
    }
    unsafe {
        mem := malloc_uncollectable(sz)
        return C.memcpy(mem, src, sz)
    }
}

pub struct GCHeapUsage {
pub:
    heap_size      usize
    free_bytes     usize
    total_bytes    usize
    unmapped_bytes usize
    bytes_since_gc usize
}

// gc_heap_usage returns the info about heap usage
pub fn gc_heap_usage() GCHeapUsage {
    $if gcboehm ? {
        mut res := GCHeapUsage{}
        C.GC_get_heap_usage_safe(&res.heap_size, &res.free_bytes, &res.unmapped_bytes,
            &res.bytes_since_gc, &res.total_bytes)
        return res
    } $else {
        return GCHeapUsage{}
    }
}

// gc_memory_use returns the total memory use in bytes by all allocated blocks
pub fn gc_memory_use() usize {
    $if gcboehm ? {
        return C.GC_get_memory_use()
    } $else {
        return 0
    }
}

[inline]
fn v_fixed_index(i int, len int) int {
    $if !no_bounds_checking {
        if i < 0 || i >= len {
            s := 'fixed array index out of range (index: ${i}, len: ${len})'
            panic(s)
        }
    }
    return i
}

// print_backtrace shows a backtrace of the current call stack on stdout
pub fn print_backtrace() {
    // At the time of backtrace_symbols_fd call, the C stack would look something like this:
    // * print_backtrace_skipping_top_frames
    // * print_backtrace itself
    // * the rest of the backtrace frames
    // => top 2 frames should be skipped, since they will not be informative to the developer
    $if !no_backtrace ? {
        $if freestanding {
            println(bare_backtrace())
        } $else {
            $if tinyc {
                C.tcc_backtrace(c'Backtrace')
            } $else {
                // NOTE: TCC doesn't have the unwind library
                $if use_libbacktrace ? {
                    print_libbacktrace(1)
                } $else {
                    print_backtrace_skipping_top_frames(2)
                }
            }
        }
    }
}

// NOTE: g_main_argc and g_main_argv are filled in right after C's main start.
// They are used internally by V's builtin; for user code, it is much
// more convenient to just use `os.args` instead.

[markused]
__global g_main_argc = int(0)

[markused]
__global g_main_argv = unsafe { nil }