module builtin

// dbghelp.h is already included in cheaders.v
#flag windows -l dbghelp

// SymbolInfo is used by print_backtrace_skipping_top_frames_msvc.
pub struct SymbolInfo {
pub mut:
    f_size_of_struct u32 // must be 88 to be recognised by SymFromAddr
    f_type_index     u32 // Type Index of symbol
    f_reserved       [2]u64
    f_index          u32
    f_size           u32
    f_mod_base       u64 // Base Address of module containing this symbol
    f_flags          u32
    f_value          u64 // Value of symbol, ValuePresent should be 1
    f_address        u64 // Address of symbol including base address of module
    f_register       u32 // register holding value or pointer to value
    f_scope          u32 // scope of the symbol
    f_tag            u32 // pdb classification
    f_name_len       u32 // Actual length of name
    f_max_name_len   u32 // must be manually set
    f_name           u8  // must be calloc(f_max_name_len)
}

pub struct SymbolInfoContainer {
pub mut:
    syminfo     SymbolInfo
    f_name_rest [254]char
}

pub struct Line64 {
pub mut:
    f_size_of_struct u32
    f_key            voidptr
    f_line_number    u32
    f_file_name      &u8 = unsafe { nil }
    f_address        u64
}

// returns the current options mask
fn C.SymSetOptions(symoptions u32) u32

// returns handle
fn C.GetCurrentProcess() voidptr

fn C.SymInitialize(h_process voidptr, p_user_search_path &u8, b_invade_process i32) i32

fn C.CaptureStackBackTrace(frames_to_skip u32, frames_to_capture u32, p_backtrace voidptr, p_backtrace_hash voidptr) u16

fn C.SymFromAddr(h_process voidptr, address u64, p_displacement voidptr, p_symbol voidptr) i32

fn C.SymGetLineFromAddr64(h_process voidptr, address u64, p_displacement voidptr, p_line &Line64) i32

// Ref - https://docs.microsoft.com/en-us/windows/win32/api/dbghelp/nf-dbghelp-symsetoptions
const symopt_undname = 0x00000002
const symopt_deferred_loads = 0x00000004
const symopt_no_cpp = 0x00000008
const symopt_load_lines = 0x00000010
const symopt_include_32bit_modules = 0x00002000
const symopt_allow_zero_address = 0x01000000
const symopt_debug = u32(0x80000000)

// print_backtrace_skipping_top_frames prints the backtrace skipping N top frames.
pub fn print_backtrace_skipping_top_frames(skipframes int) bool {
    $if msvc {
        return print_backtrace_skipping_top_frames_msvc(skipframes)
    }
    $if tinyc {
        return print_backtrace_skipping_top_frames_tcc(skipframes)
    }
    $if mingw {
        return print_backtrace_skipping_top_frames_mingw(skipframes)
    }
    eprintln('print_backtrace_skipping_top_frames is not implemented')
    return false
}

@[direct_array_access]
fn print_backtrace_skipping_top_frames_msvc(skipframes int) bool {
    $if msvc {
        mut offset := u64(0)
        backtraces := [100]voidptr{}
        sic := SymbolInfoContainer{}
        mut si := &sic.syminfo
        si.f_size_of_struct = sizeof(SymbolInfo) // Note: C.SYMBOL_INFO is 88
        si.f_max_name_len = sizeof(SymbolInfoContainer) - sizeof(SymbolInfo) - 1
        fname := &char(&si.f_name)
        mut sline64 := Line64{
            f_file_name: &u8(unsafe { nil })
        }
        sline64.f_size_of_struct = sizeof(Line64)

        handle := C.GetCurrentProcess()
        defer {
            C.SymCleanup(handle)
        }

        C.SymSetOptions(symopt_debug | symopt_load_lines | symopt_undname)

        syminitok := C.SymInitialize(handle, 0, 1)
        if syminitok != 1 {
            eprintln('Failed getting process: Aborting backtrace.\n')
            return false
        }

        frames := int(C.CaptureStackBackTrace(skipframes + 1, 100, &backtraces[0], 0))
        if frames < 2 {
            eprintln('C.CaptureStackBackTrace returned less than 2 frames')
            return false
        }
        for i in 0 .. frames {
            frame_addr := backtraces[i]
            if C.SymFromAddr(handle, frame_addr, &offset, si) == 1 {
                nframe := frames - i - 1
                mut lineinfo := ''
                if C.SymGetLineFromAddr64(handle, frame_addr, &offset, &sline64) == 1 {
                    file_name := unsafe { tos3(sline64.f_file_name) }
                    lnumber := sline64.f_line_number
                    lineinfo = file_name + ':' + i64(lnumber).str()
                } else {
                    // addr:
                    lineinfo = '?? : address = 0x' + ptr_str(frame_addr)
                }
                sfunc := demangle_v_symbol(unsafe { tos3(fname) })
                snframe := i64(nframe).str()
                eprint_space_padding(snframe, 2)
                eprint(': ')
                eprint(sfunc)
                eprint_space_padding(sfunc, 25)
                eprint('  ')
                eprintln(lineinfo)
            } else {
                // https://docs.microsoft.com/en-us/windows/win32/debug/system-error-codes
                cerr := int(C.GetLastError())
                eprint('SymFromAddr failure: ')
                eprint(i64(cerr).str())
                if cerr == 87 {
                    eprintln(' = The parameter is incorrect)')
                } else if cerr == 487 {
                    // probably caused because the .pdb isn't in the executable folder
                    eprintln(' = Attempt to access invalid address (Verify that you have the .pdb file in the right folder.)')
                } else {
                    eprintln(' (see https://docs.microsoft.com/en-us/windows/win32/debug/system-error-codes)')
                }
            }
        }
        return true
    } $else {
        eprintln('print_backtrace_skipping_top_frames_msvc must be called only when the compiler is msvc')
        return false
    }
}

fn print_backtrace_skipping_top_frames_mingw(skipframes int) bool {
    eprintln('print_backtrace_skipping_top_frames_mingw is not implemented')
    return false
}

fn C.tcc_backtrace(fmt &char) i32

fn print_backtrace_skipping_top_frames_tcc(skipframes int) bool {
    $if tinyc {
        $if no_backtrace ? {
            eprintln('backtraces are disabled')
            return false
        } $else {
            C.tcc_backtrace(c'Backtrace')
            return true
        }
    } $else {
        eprintln('print_backtrace_skipping_top_frames_tcc must be called only when the compiler is tcc')
        return false
    }
    // Not reachable, but it looks like it's not detectable by V
    return false
}