// Copyright (c) 2019-2024 Alexander Medvednikov. All rights reserved.
// Use of this source code is governed by an MIT license
// that can be found in the LICENSE file.
module pref

import os
import strings
import v.vcache

pub const default_module_path = os.vmodules_dir()

pub fn new_preferences() &Preferences {
    mut p := &Preferences{}
    p.fill_with_defaults()
    return p
}

const windows_default_gc_defines = ['gcboehm', 'gcboehm_full', 'gcboehm_incr', 'gcboehm_opt',
    'gcboehm_leak', 'vgc']

fn (p &Preferences) default_thread_stack_size() int {
    return match p.arch {
        .arm32, .rv32, .i386, .ppc, .wasm32 { 2 * 1024 * 1024 }
        else { 8 * 1024 * 1024 }
    }
}

fn (p &Preferences) is_linux_wayland_only_session() bool {
    if p.os != .linux {
        return false
    }
    if os.getenv('DISPLAY') != '' {
        return false
    }
    return os.getenv('WAYLAND_DISPLAY') != ''
        || os.getenv('XDG_SESSION_TYPE').to_lower() == 'wayland'
}

fn (mut p Preferences) expand_lookup_paths() {
    if p.vroot == '' {
        // Location of all vlib files
        p.vroot = os.dir(vexe_path())
    }
    p.vlib = os.join_path(p.vroot, 'vlib')
    p.vmodules_paths = os.vmodules_paths()

    if p.lookup_path.len == 0 {
        p.lookup_path = ['@vlib', '@vmodules']
    }
    mut expanded_paths := []string{}
    for path in p.lookup_path {
        match path {
            '@vlib' { expanded_paths << p.vlib }
            '@vmodules' { expanded_paths << p.vmodules_paths }
            else { expanded_paths << path.replace('@vroot', p.vroot) }
        }
    }
    p.lookup_path = expanded_paths
}

fn (mut p Preferences) expand_exclude_paths() {
    mut res := []string{}
    static_replacement_list := ['@vroot', p.vroot, '@vlib', p.vlib]
    for x in p.exclude {
        y := x.replace_each(static_replacement_list)
        if y.contains('@vmodules') {
            // @vmodules is a list of paths, each of which should be expanded in the complete exclusion list:
            for vmp in p.vmodules_paths {
                res << y.replace('@vmodules', vmp)
            }
            continue
        }
        res << y
    }
    p.exclude = res
}

fn (mut p Preferences) setup_os_and_arch_when_not_explicitly_set() {
    if p.os == .wasm32_emscripten {
        // TODO: remove after `$if wasm32_emscripten {` works
        p.parse_define('emscripten')
    }
    host_os := if p.backend == .wasm { OS.wasi } else { get_host_os() }
    if p.os == ._auto {
        p.os = host_os
        p.build_options << '-os ${host_os.lower()}'
    }

    if !p.output_cross_c && p.os != host_os {
        if p.os == .linux && p.arch == ._auto {
            // The bundled linuxroot sysroot currently only contains x86_64 runtime files.
            p.set_default_arch(.amd64)
        }
        // TODO: generalise this not only for macos->linux, after considering the consequences for vab/Android:
        if host_os == .macos && p.os == .linux {
            p.parse_define('use_bundled_libgc')
        }
    }
}

fn (mut p Preferences) set_default_arch(arch Arch) {
    if p.arch != ._auto || arch == ._auto {
        return
    }
    p.arch = arch
    p.build_options << '-arch ${arch}'
}

fn arch_from_ccompiler_name(ccompiler string) Arch {
    name := os.file_name(ccompiler).to_lower_ascii()
    if name.contains('x86_64') || name.contains('amd64') {
        return .amd64
    }
    if name.contains('aarch64') || name.contains('arm64-v8a') || name.contains('arm64') {
        return .arm64
    }
    if name.contains('armeabi-v7a') || name.contains('armv7')
        || name.contains('arm-linux-androideabi') || name.contains('arm32') {
        return .arm32
    }
    if name.contains('riscv64') {
        return .rv64
    }
    if name.contains('riscv32') {
        return .rv32
    }
    if name.contains('i686') || name.contains('i386') || name.contains('x86') {
        return .i386
    }
    if name.contains('s390x') {
        return .s390x
    }
    if name.contains('ppc64le') {
        return .ppc64le
    }
    if name.contains('loongarch64') {
        return .loongarch64
    }
    if name.contains('sparc64') {
        return .sparc64
    }
    if name.contains('ppc64') {
        return .ppc64
    }
    return ._auto
}

fn (mut p Preferences) resolve_default_arch() {
    if p.arch != ._auto {
        return
    }
    host_os := if p.backend == .wasm { OS.wasi } else { get_host_os() }
    if p.os != host_os {
        p.set_default_arch(arch_from_ccompiler_name(p.ccompiler))
    }
    p.set_default_arch(get_host_arch())
}

pub fn (mut p Preferences) defines_map_unique_keys() string {
    mut defines_map := map[string]bool{}
    for d in p.compile_defines {
        defines_map[d] = true
    }
    for d in p.compile_defines_all {
        defines_map[d] = true
    }
    keys := defines_map.keys()
    skeys := keys.sorted()
    return skeys.join(',')
}

fn (mut p Preferences) disable_tcc_shared_backtraces() {
    if p.is_shared && p.ccompiler_type == .tinyc && 'no_backtrace' !in p.compile_defines_all {
        // TCC shared libraries should not depend on TCC's backtrace runtime symbols.
        p.parse_define('no_backtrace')
    }
}

// fill_with_defaults initializes unset preferences and derives build options from them.
pub fn (mut p Preferences) fill_with_defaults() {
    p.setup_os_and_arch_when_not_explicitly_set()
    p.expand_lookup_paths()
    p.expand_exclude_paths()
    rpath := os.real_path(p.path)
    if p.out_name == '' {
        target_dir := if os.is_dir(rpath) { rpath } else { os.dir(rpath) }
        p.out_name = os.join_path(target_dir, p.default_output_name(rpath))
        // Do *NOT* be tempted to generate binaries in the current work folder,
        // when -o is not given by default, like Go, Clang, GCC etc do.
        //
        // These compilers also are frequently used with an external build system,
        // in part because of that shortcoming, to ensure that they work in a
        // predictable work folder/environment.
        //
        // In comparison, with V, building an executable by default places it
        // next to its source code, so that it can be used directly with
        // functions like `os.resource_abs_path()` and `os.executable()` to
        // locate resources relative to it. That enables running examples like
        // this:
        // `./v run examples/flappylearning/`
        // instead of:
        // `./v -o examples/flappylearning/flappylearning run examples/flappylearning/`
        // This topic comes up periodically from time to time on Discord, and
        // many CI breakages already happened, when someone decides to make V
        // behave in this aspect similarly to the dumb behaviour of other
        // compilers.
        //
        // If you do decide to break it, please *at the very least*, test it
        // extensively, and make a PR about it, instead of committing directly
        // and breaking the CI, VC, and users doing `v up`.
    } else if p.out_name_is_dir {
        p.out_name = os.join_path(p.out_name, p.default_output_name(rpath))
    }
    npath := rpath.replace('\\', '/')
    p.building_v = !p.is_repl && (npath.ends_with('cmd/v') || npath.ends_with('cmd/tools/vfmt.v'))
    if p.os == .linux {
        $if !linux {
            p.parse_define('cross_compile')
        }
    }
    if p.output_cross_c {
        // avoid linking any GC related code, since the target may not have an usable GC system
        p.gc_mode = .no_gc
        p.use_cache = false
        p.skip_unused = false
        p.parse_define('no_backtrace') // the target may not have usable backtrace() and backtrace_symbols()
        p.parse_define('cross') // TODO: remove when `$if cross {` works
    }
    if p.gc_mode == .unknown {
        if p.backend != .c || p.building_v || p.is_bare || p.os == .windows || p.is_musl {
            p.gc_mode = .no_gc
            p.build_options << ['-gc', 'none']
        } else {
            // enable the GC by default
            p.gc_mode = .boehm_full_opt
            // NOTE: these are added to p.compile_defines[_all]
            // more than once when building modules for usecache
            p.parse_define('gcboehm')
            p.parse_define('gcboehm_full')
            p.parse_define('gcboehm_opt')
        }
    }
    if p.is_debug {
        p.parse_define('debug')
    }
    p.try_to_use_tcc_by_default()
    if p.ccompiler == '' {
        p.default_c_compiler()
    }
    if p.cppcompiler == '' {
        p.default_cpp_compiler()
    }
    p.find_cc_if_cross_compiling()
    p.resolve_default_arch()
    if !p.thread_stack_size_set_by_flag {
        p.thread_stack_size = p.default_thread_stack_size()
    }
    p.ccompiler_type = cc_from_string(p.ccompiler)
    p.normalize_gc_defaults_for_resolved_ccompiler()
    p.is_test = p.path.ends_with('_test.v') || p.path.ends_with('_test.vv')
        || p.path.all_before_last('.v').all_before_last('.').ends_with('_test')
    p.is_vsh = p.path.ends_with('.vsh') || p.raw_vsh_tmp_prefix != ''
    p.is_script = p.is_vsh || p.path.ends_with('.v') || p.path.ends_with('.vv')
    if p.third_party_option == '' {
        p.third_party_option = p.cflags
        $if !windows {
            if !p.third_party_option.contains('-fPIC') {
                p.third_party_option += ' -fPIC'
            }
        }
    }

    final_os := p.os.lower()
    p.parse_define(final_os)
    if p.is_linux_wayland_only_session() && 'linux_wayland_session' !in p.compile_defines_all {
        p.parse_define('linux_wayland_session')
    }

    // Prepare the cache manager. All options that can affect the generated cached .c files
    // should go into res.cache_manager.vopts, which is used as a salt for the cache hash.
    vhash := @VHASH
    p.cache_manager = vcache.new_cache_manager([
        vhash,
        // ensure that different v versions use separate build artefacts
        '${p.backend} | ${final_os} | ${p.ccompiler} | ${p.is_prod} | ${p.sanitize}',
        p.defines_map_unique_keys(),
        p.cflags.trim_space(),
        p.third_party_option.trim_space(),
        p.lookup_path.str(),
    ])
    // eprintln('prefs.cache_manager: ${p}')
    // disable use_cache for specific cases:
    if os.user_os() == 'windows' {
        p.use_cache = false
    }
    if p.build_mode == .build_module {
        // eprintln('-usecache and build-module flags are not compatible')
        p.use_cache = false
    }
    if p.is_shared {
        // eprintln('-usecache and -shared flags are not compatible')
        p.use_cache = false
    }
    if p.bare_builtin_dir == '' && p.os == .wasm32 {
        p.bare_builtin_dir = os.join_path(p.vroot, 'vlib', 'builtin', 'wasm_bare')
    } else if p.bare_builtin_dir == '' {
        p.bare_builtin_dir = os.join_path(p.vroot, 'vlib', 'builtin', 'linux_bare')
    }

    $if prealloc {
        if !p.no_parallel && p.is_verbose {
            eprintln('disabling parallel cgen, since V was built with -prealloc')
        }
        p.no_parallel = true
    }
}

// normalize_gc_defaults_for_resolved_ccompiler clears stale compiler-dependent
// defaults after the effective C compiler has been resolved.
pub fn (mut p Preferences) normalize_gc_defaults_for_resolved_ccompiler() {
    p.disable_tcc_shared_backtraces()
    if p.prealloc {
        p.gc_mode = .no_gc
        p.clear_gc_options()
        return
    }
    if p.os != .windows || p.ccompiler_type != .msvc || p.gc_set_by_flag {
        return
    }
    p.gc_mode = .no_gc
    p.clear_gc_options()
}

fn (p &Preferences) default_output_name(rpath string) string {
    filename := os.file_name(rpath).trim_space()
    mut base := filename.all_before_last('.')
    if os.file_ext(base) in ['.c', '.js', '.wasm'] {
        base = base.all_before_last('.')
    }
    if base == '' {
        // The file name is just `.v` or `.vsh` or `.*`
        base = filename
    }
    if needs_safe_default_output_name(base, filename, rpath) {
        base = safe_default_output_name(filename)
    }
    if p.raw_vsh_tmp_prefix != '' {
        return p.raw_vsh_tmp_prefix + '.' + base
    }
    return base
}

fn needs_safe_default_output_name(base string, filename string, rpath string) bool {
    if base == '' || base in ['.', '..', '-'] {
        return true
    }
    if base == filename && filename.starts_with('.') && !os.is_dir(rpath) {
        return true
    }
    if base.ends_with('.c') || base.ends_with('.js') || base.ends_with('.wasm') {
        return true
    }
    for ch in base {
        if ch < ` ` || ch == 127 {
            return true
        }
    }
    return false
}

fn safe_default_output_name(filename string) string {
    mut sanitized := strings.new_builder(filename.len + 4)
    for ch in filename {
        if ch < ` ` || ch == 127 {
            sanitized.write_u8(`_`)
        } else {
            sanitized.write_u8(ch)
        }
    }
    sanitized.write_string('.out')
    return sanitized.str()
}

fn (mut p Preferences) find_cc_if_cross_compiling() {
    if p.os == get_host_os() {
        return
    }
    if p.ccompiler_set_by_flag {
        // Only mingw compilers can cross-compile for Windows (others lack Windows headers),
        // so override any non-mingw compiler with the proper cross-compiler.
        if p.os == .windows && !p.ccompiler.contains('mingw') {
            p.ccompiler = p.vcross_compiler_name()
            return
        }
        // Respect explicit `-cc` selection even in cross-compilation mode.
        return
    }
    if p.os == .windows && p.ccompiler == 'msvc' {
        // Allow for explicit overrides like `v -showcc -cc msvc -os windows file.v`,
        // this makes flag passing more easily debuggable on other OSes too, not only
        // on windows (building will stop later, when -showcc already could display all
        // options).
        return
    }
    p.ccompiler = p.vcross_compiler_name()
}

fn (mut p Preferences) try_to_use_tcc_by_default() {
    preferred_tcc := default_tcc_compiler()
    if p.ccompiler == 'tcc' {
        p.ccompiler = if preferred_tcc != '' { preferred_tcc } else { 'tcc' }
        return
    }
    if p.ccompiler == '' {
        // -prealloc uses thread-local allocator state. The bundled tcc does not
        // support TLS declarations, so use the platform C compiler by default.
        if p.prealloc {
            return
        }
        // use an optimizing compiler (i.e. gcc or clang) on -prod mode
        if p.is_prod {
            return
        }
        p.ccompiler = preferred_tcc
        return
    }
}

fn usable_system_tcc_compiler() string {
    if get_host_os() != .termux {
        return ''
    }
    system_tcc := os.find_abs_path_of_executable('tcc') or { return '' }
    tcc_probe := os.execute('${os.quoted_path(system_tcc)} -v')
    if tcc_probe.exit_code != 0 {
        return ''
    }
    return system_tcc
}

fn usable_bundled_tcc_compiler(vroot string) string {
    vtccexe := os.join_path(vroot, 'thirdparty', 'tcc', 'tcc.exe')
    if !os.is_file(vtccexe) || !os.is_executable(vtccexe) {
        return ''
    }
    // Unsupported hosts can still have a placeholder `thirdparty/tcc/` checkout.
    tcc_probe := os.execute('${os.quoted_path(vtccexe)} -v')
    if tcc_probe.exit_code != 0 {
        return ''
    }
    return vtccexe
}

// default_tcc_compiler returns the preferred TinyCC path when it exists and works on the host.
pub fn default_tcc_compiler() string {
    vexe := vexe_path()
    vroot := os.dir(vexe)
    bundled_tcc := usable_bundled_tcc_compiler(vroot)
    if bundled_tcc != '' {
        return bundled_tcc
    }
    return usable_system_tcc_compiler()
}

fn (mut p Preferences) clear_gc_options() {
    p.compile_defines = p.compile_defines.filter(it !in windows_default_gc_defines)
    p.compile_defines_all = p.compile_defines_all.filter(it !in windows_default_gc_defines)
    for define in windows_default_gc_defines {
        p.compile_values.delete(define)
    }
    mut build_options := []string{cap: p.build_options.len + 2}
    mut i := 0
    for i < p.build_options.len {
        option := p.build_options[i]
        if option == '-gc' {
            i += 2
            continue
        }
        if option.starts_with('-gc ') {
            i++
            continue
        }
        if option.starts_with('-d ') {
            define := option[3..].all_before('=')
            if define in windows_default_gc_defines {
                i++
                continue
            }
        }
        build_options << option
        i++
    }
    build_options << ['-gc', 'none']
    p.build_options = build_options
}

pub fn (mut p Preferences) default_c_compiler() {
    // TODO: fix $if after 'string'
    $if windows {
        p.ccompiler = 'gcc'
        return
    }
    if p.os == .ios {
        $if !ios {
            ios_sdk := if p.is_ios_simulator { 'iphonesimulator' } else { 'iphoneos' }
            ios_sdk_path_res := os.execute_or_exit('xcrun --sdk ${ios_sdk} --show-sdk-path')
            mut isysroot := ios_sdk_path_res.output.replace('\n', '')
            arch := if p.is_ios_simulator {
                '-arch x86_64 -arch arm64'
            } else {
                '-arch armv7 -arch armv7s -arch arm64'
            }
            // On macOS, /usr/bin/cc is a hardlink/wrapper for xcrun. clang on darwin hosts
            // will automatically change the build target based off of the selected sdk, making xcrun -sdk iphoneos pointless
            p.ccompiler = '/usr/bin/cc'
            p.cflags = '-isysroot ${isysroot} ${arch}' + p.cflags
            return
        }
    }
    p.ccompiler = 'cc'
    return
}

pub fn (mut p Preferences) default_cpp_compiler() {
    if p.ccompiler.contains('clang') {
        p.cppcompiler = 'clang++'
        return
    }
    p.cppcompiler = 'c++'
}

pub fn vexe_path() string {
    vexe := os.getenv('VEXE')
    if vexe != '' {
        return vexe
    }
    myexe := os.executable()
    mut real_vexe_path := myexe
    for {
        $if tinyc {
            $if x32 {
                // TODO: investigate why exactly tcc32 segfaults on os.real_path here,
                // and remove this cludge.
                break
            }
        }
        real_vexe_path = os.real_path(real_vexe_path)
        break
    }
    os.setenv('VEXE', real_vexe_path, true)
    return real_vexe_path
}

pub fn (p &Preferences) vcross_linker_name() string {
    vlname := os.getenv('VCROSS_LINKER_NAME')
    if vlname != '' {
        return vlname
    }
    $if macos {
        return '/opt/homebrew/opt/llvm/bin/ld.lld'
    }
    $if windows {
        return 'ld.lld.exe'
    }
    return 'ld.lld'
}

pub fn (p &Preferences) vcross_compiler_name() string {
    vccname := os.getenv('VCROSS_COMPILER_NAME')
    if vccname != '' {
        return vccname
    }
    if p.os == .windows {
        if p.os == .freebsd {
            return 'clang'
        }
        if p.m64 {
            return 'x86_64-w64-mingw32-gcc'
        }
        return 'i686-w64-mingw32-gcc'
    }
    if p.os == .linux {
        return 'clang'
    }
    if p.os == .freebsd {
        return 'clang'
    }
    if p.os == .wasm32_emscripten {
        if os.user_os() == 'windows' {
            return 'emcc.bat'
        }
        return 'emcc'
    }
    if p.backend == .c && !p.out_name.ends_with('.c') {
        eprintln('Note: V can only cross compile to Windows and Linux for now by default.')
        eprintln('It will use `cc` as a cross compiler for now, although that will probably fail.')
        eprintln('Set `VCROSS_COMPILER_NAME` to the name of your cross compiler, for your target OS: ${p.os} .')
    }
    return 'cc'
}

// vroot_file reads the given file, given a path relative to @VEXEROOT .
// Its goal is to give all backends a shared infrastructure to read their own static preludes (like C headers etc),
// without each having to implement their own way of lookup/embedding/caching them.
pub fn (mut p Preferences) vroot_file(path string) string {
    full_path := os.join_path(p.vroot, path)
    return os.read_file(full_path) or { '/* missing @VEXEROOT content of path: ${full_path} */' }
}