module builtin

// print_backtrace_skipping_top_frames prints the backtrace skipping N top frames.
pub fn print_backtrace_skipping_top_frames(xskipframes int) bool {
    $if no_backtrace ? {
        return false
    } $else {
        skipframes := xskipframes + 2
        $if macos || freebsd || openbsd || netbsd {
            return print_backtrace_skipping_top_frames_bsd(skipframes)
        } $else $if linux {
            return print_backtrace_skipping_top_frames_linux(skipframes)
        } $else {
            println('print_backtrace_skipping_top_frames is not implemented. skipframes: ${skipframes}')
        }
    }
    return false
}

// the functions below are not called outside this file,
// so there is no need to have their twins in builtin_windows.v
@[direct_array_access]
fn print_backtrace_skipping_top_frames_bsd(skipframes int) bool {
    $if no_backtrace ? {
        return false
    } $else {
        $if macos || freebsd || netbsd {
            buffer := [100]voidptr{}
            nr_ptrs := C.backtrace(&buffer[0], 100)
            if nr_ptrs < 2 {
                eprintln('C.backtrace returned less than 2 frames')
                return false
            }
            nr_actual_frames := nr_ptrs - skipframes
            csymbols := C.backtrace_symbols(voidptr(&buffer[skipframes]), nr_actual_frames)
            atos_lines := bsd_backtrace_resolve_atos(&buffer[skipframes], nr_actual_frames)
            for i in 0 .. nr_actual_frames {
                sframe := unsafe { tos2(&u8(csymbols[i])) }
                mut file_line := ''
                if i < atos_lines.len {
                    file_line = atos_lines[i]
                }
                // macOS format: `0   main   0x00000001047232f8 veb__run_T_main__App_main__Context + 356`
                symbol_start := sframe.index('0x') or { -1 }
                if symbol_start < 0 {
                    continue
                }
                rest := sframe[symbol_start..]
                space_after_addr := rest.index(' ') or { -1 }
                if space_after_addr < 0 {
                    continue
                }
                symbol_and_offset := rest[space_after_addr + 1..]
                plus_pos := symbol_and_offset.index(' + ') or { -1 }
                mut raw_symbol := symbol_and_offset
                if plus_pos >= 0 {
                    raw_symbol = symbol_and_offset[..plus_pos]
                }
                // Skip C runtime frames that are not V functions:
                if raw_symbol in ['main', 'start', '_main'] {
                    continue
                }
                mut demangled := ''
                if plus_pos >= 0 {
                    demangled = demangle_v_symbol(raw_symbol) + symbol_and_offset[plus_pos..]
                } else {
                    demangled = demangle_v_symbol(raw_symbol)
                }
                if file_line.len > 0 {
                    eprint(file_line)
                    eprint_space_padding(file_line, 45)
                    eprint(' | ')
                    eprintln(demangled)
                } else {
                    eprintln(demangled)
                }
            }
            if nr_actual_frames > 0 {
                unsafe { C.free(csymbols) }
            }
        }
        return true
    }
}

// bsd_backtrace_resolve_atos uses macOS `atos` to resolve addresses to file:line info.
// Returns an array of file:line strings (one per frame). Empty string if unresolved.
@[direct_array_access]
fn bsd_backtrace_resolve_atos(buffer &voidptr, nr_frames int) []string {
    $if macos {
        exe_name := backtrace_current_executable_name()
        if exe_name.len == 0 {
            return []string{}
        }
        base_addr := voidptr(C._dyld_get_image_header(0))
        if base_addr == unsafe { nil } {
            return []string{}
        }
        // Build single atos command with all addresses for efficiency:
        mut cmd := 'atos --fullPath -o "' + exe_name + '" -l ' + ptr_str(base_addr)
        for i in 0 .. nr_frames {
            cmd += ' ' + ptr_str(unsafe { buffer[i] })
        }
        f := C.popen(&char(cmd.str), c'r')
        if f == unsafe { nil } {
            return []string{}
        }
        buf := [4096]u8{}
        mut lines := []string{cap: nr_frames}
        unsafe {
            bp := &u8(&buf[0])
            for C.fgets(&char(bp), 4096, f) != 0 {
                line := tos(bp, vstrlen(bp)).trim_chars(' \t\n\r', .trim_both)
                // atos output format: `func_name (in binary) (file.v:42)`
                // Extract the last parenthesized (file:line) part:
                paren_pos := line.index_last_('(')
                if paren_pos >= 0 {
                    file_part := line[paren_pos + 1..]
                    end_paren := file_part.index_last_(')')
                    if end_paren >= 0 {
                        file_line := file_part[..end_paren]
                        if file_line.contains(':') && !file_line.starts_with('in ')
                            && !file_line.contains('.tmp.c:') {
                            lines << file_line
                            continue
                        }
                    }
                }
                lines << ''
            }
        }
        C.pclose(f)
        return lines
    }
    return []string{}
}

fn C.tcc_backtrace(fmt &char) i32

fn backtrace_current_executable_name() string {
    args := arguments()
    if args.len == 0 {
        return ''
    }
    return args[0]
}

fn backtrace_addr2line_executable(executable string, current_executable_name string) string {
    if executable.len == 0 {
        return '/proc/self/exe'
    }
    if executable.contains('/') {
        return executable
    }
    if current_executable_name.len > 0
        && executable.all_after_last('/') == current_executable_name.all_after_last('/') {
        return '/proc/self/exe'
    }
    return executable
}

@[direct_array_access]
fn print_backtrace_skipping_top_frames_linux(skipframes int) bool {
    $if android {
        eprintln('On Android no backtrace is available.')
        return false
    }
    $if no_backtrace ? {
        return false
    } $else {
        $if linux && !freestanding {
            $if tinyc {
                C.tcc_backtrace(c'Backtrace')
                return false
            } $else {
                $if !glibc {
                    eprintln('backtrace_symbols is missing => printing backtraces is not available.')
                    eprintln('Some libc implementations like musl simply do not provide it.')
                    return false
                } $else {
                    current_executable_name := backtrace_current_executable_name()
                    buffer := [100]voidptr{}
                    nr_ptrs := C.backtrace(&buffer[0], 100)
                    if nr_ptrs < 2 {
                        eprintln('C.backtrace returned less than 2 frames')
                        return false
                    }
                    nr_actual_frames := nr_ptrs - skipframes
                    //////csymbols := backtrace_symbols(*voidptr(&buffer[skipframes]), nr_actual_frames)
                    csymbols := C.backtrace_symbols(voidptr(&buffer[skipframes]), nr_actual_frames)
                    for i in 0 .. nr_actual_frames {
                        sframe := unsafe { tos2(&u8(csymbols[i])) }
                        executable := sframe.all_before('(')
                        addr2line_executable := backtrace_addr2line_executable(executable,
                            current_executable_name)
                        addr := sframe.all_after('[').all_before(']')
                        beforeaddr := sframe.all_before('[')
                        cmd := 'addr2line -e ' + addr2line_executable + ' ' + addr
                        // taken from os, to avoid depending on the os module inside builtin.v
                        f := C.popen(&char(cmd.str), c'r')
                        if f == unsafe { nil } {
                            eprintln(sframe)
                            continue
                        }
                        buf := [1000]u8{}
                        mut output := ''
                        unsafe {
                            bp := &u8(&buf[0])
                            for C.fgets(&char(bp), 1000, f) != 0 {
                                output += tos(bp, vstrlen(bp))
                            }
                        }
                        output = output.trim_chars(' \t\n', .trim_both) + ':'
                        if C.pclose(f) != 0 {
                            eprintln(sframe)
                            continue
                        }
                        if output in ['??:0:', '??:?:'] {
                            output = ''
                        }
                        // See http://wiki.dwarfstd.org/index.php?title=Path_Discriminators
                        // Note: it is shortened here to just d. , just so that it fits, and so
                        // that the common error file:lineno: line format is enforced.
                        output = output.replace(' (discriminator', ': (d.')
                        eprint(output)
                        eprint_space_padding(output, 55)
                        eprint(' | ')
                        eprint(addr)
                        eprint(' | ')
                        eprintln(demangle_backtrace_sym(beforeaddr))
                    }
                    if nr_actual_frames > 0 {
                        unsafe { C.free(csymbols) }
                    }
                }
            }
        }
    }
    return true
}