module builder

import os
import v.token
import v.pref
import v.errors
import v.util
import v.ast
import v.ast.walker
import v.vmod
import v.checker
import v.transformer
import v.comptime
import v.generics
import v.parser
import v.markused
import v.depgraph
import v.callgraph
import v.dotgraph
// import x.json2

fn append_map_array(mut items map[string][]string, key string, value string) {
    if key !in items {
        items[key] = []string{}
    }
    items[key] << value
}

pub struct Builder {
pub:
    compiled_dir string // contains os.real_path() of the dir of the final file being compiled, or the dir itself when doing `v .`
    module_path  string
pub mut:
    checker             &checker.Checker         = unsafe { nil }
    transformer         &transformer.Transformer = unsafe { nil }
    comptime            &comptime.Comptime       = unsafe { nil }
    generics            &generics.Generics       = unsafe { nil }
    out_name_c          string
    out_name_js         string
    stats_lines         int // size of backend generated source code in lines
    stats_bytes         int // size of backend generated source code in bytes
    nr_errors           int // accumulated error count of scanner, parser, checker, and builder
    nr_warnings         int // accumulated warning count of scanner, parser, checker, and builder
    nr_notices          int // accumulated notice count of scanner, parser, checker, and builder
    pref                &pref.Preferences = unsafe { nil }
    module_search_paths []string
    parsed_files        []&ast.File
    //$if windows {
    cached_msvc MsvcResult
    //}
    table     &ast.Table = unsafe { nil }
    ccoptions CcompilerOptions
    // Note: changes in mod `builtin` force invalidation of every other .v file
    mod_invalidates_paths map[string][]string // changes in mod `os`, invalidate only .v files, that do `import os`
    mod_invalidates_mods  map[string][]string // changes in mod `os`, force invalidation of mods, that do `import os`
    path_invalidates_mods map[string][]string // changes in a .v file from `os`, invalidates `os`
    crun_cache_keys       []string            // target executable + top level source files; filled in by Builder.should_rebuild
    executable_exists     bool                // if the executable already exists, don't remove new executable after `v run`
    str_args              string              // for parallel_cc mode only, to know which cc args to use (like -I etc)
    disable_flto          bool
}

struct CFunctionCallCollector {
mut:
    names map[string]bool
}

fn c_function_call_collector_visit(node &ast.Node, data voidptr) bool {
    mut c := unsafe { &CFunctionCallCollector(data) }
    if node is ast.Expr && node is ast.CallExpr {
        call := node as ast.CallExpr
        if call.name.starts_with('C.') {
            c.names[call.name] = true
        }
    }
    return true
}

pub fn new_builder(pref_ &pref.Preferences) Builder {
    rdir := os.real_path(pref_.path)
    compiled_dir := if os.is_dir(rdir) { rdir } else { os.dir(rdir) }
    mut table := ast.new_table()
    table.is_fmt = false
    if pref_.use_color == .always {
        util.emanager.set_support_color(true)
    }
    if pref_.use_color == .never {
        util.emanager.set_support_color(false)
    }
    table.pointer_size = if pref_.m64 && pref_.backend != .wasm { 8 } else { 4 }
    mut msvc := MsvcResult{}
    if pref_.ccompiler_type == .msvc || pref.cc_from_string(pref_.ccompiler) == .msvc {
        $if windows {
            msvc = find_msvc(pref_.m64) or {
                MsvcResult{
                    valid: false
                }
            }
        }
    }
    util.timing_set_should_print(pref_.show_timings || pref_.is_verbose)
    if pref_.show_callgraph || pref_.show_depgraph {
        dotgraph.start_digraph()
    }
    mut executable_name := pref_.out_name
    $if windows {
        executable_name += '.exe'
    }
    return Builder{
        pref:              pref_
        table:             table
        checker:           checker.new_checker(table, pref_)
        transformer:       transformer.new_transformer_with_table(table, pref_)
        comptime:          comptime.new_comptime_with_table(table, pref_)
        generics:          generics.new_generics_with_table(table, pref_)
        compiled_dir:      compiled_dir
        cached_msvc:       msvc
        executable_exists: os.is_file(executable_name)
    }
}

fn (v &Builder) msvc_object_path(path string) string {
    path_without_obj_postfix := if path.ends_with('.obj') {
        path[..path.len - 4]
    } else if path.ends_with('.o') {
        path[..path.len - 2]
    } else {
        path
    }
    return os.real_path(if v.pref.is_debug {
        // MSVC debug builds use /MDd, so they need their own thirdparty object files.
        '${path_without_obj_postfix}.debug.obj'
    } else {
        '${path_without_obj_postfix}.obj'
    })
}

fn (mut v Builder) msvc_thirdparty_obj_path(mod string, path string, cached_path string) string {
    base_path := if cached_path != '' {
        cached_path
    } else {
        // Reuse the cache-derived .o path so different targets/options do not share one .obj.
        v.pref.cache_manager.mod_postfix_with_key2cpath(mod, '.o', os.real_path(path))
    }
    return v.msvc_object_path(base_path)
}

pub fn (mut b Builder) interpret_text(code string, v_files []string) ! {
    b.parsed_files = parser.parse_files(v_files, mut b.table, b.pref)
    b.parsed_files << parser.parse_text(code, '', mut b.table, .skip_comments, b.pref)
    if b.should_stop_after_frontend_error() && b.has_frontend_errors() {
        exit(1)
    }
    b.parse_imports()
    b.check_unused_imports()
    b.print_frontend_builder_errors()
    if b.should_stop_after_frontend_error() && b.has_frontend_errors() {
        exit(1)
    }

    if b.pref.only_check_syntax {
        return error_with_code('stop_after_parser', 7001)
    }

    b.middle_stages()!
}

pub fn (mut b Builder) front_stages(v_files []string) ! {
    mut timers := util.get_timers()
    util.timing_start('ALL_FRONT_STAGES')
    defer {
        timers.show('ALL_FRONT_STAGES')
    }
    util.timing_start('PARSE')

    util.timing_start('Builder.front_stages.parse_files')
    b.parsed_files = parser.parse_files(v_files, mut b.table, b.pref)
    timers.show('Builder.front_stages.parse_files')
    if b.should_stop_after_frontend_error() && b.has_frontend_errors() {
        exit(1)
    }

    b.parse_imports()
    b.check_unused_imports()
    b.print_frontend_builder_errors()
    if b.should_stop_after_frontend_error() && b.has_frontend_errors() {
        exit(1)
    }

    timers.show('SCAN')
    timers.show('PARSE')
    timers.show_if_exists('PARSE stmt')
    if b.pref.only_check_syntax {
        return error_with_code('stop_after_parser', 7001)
    }
}

pub fn (mut b Builder) middle_stages() ! {
    util.timing_start('CHECK')

    util.timing_start('Checker.generic_insts_to_concrete')
    b.table.generic_insts_to_concrete()
    util.timing_measure('Checker.generic_insts_to_concrete')

    b.checker.check_files(b.parsed_files)
    util.timing_start('Checker.generic_insts_to_concrete.after_check')
    b.table.generic_insts_to_concrete()
    util.timing_measure('Checker.generic_insts_to_concrete.after_check')
    util.timing_measure('CHECK')
    $if trace_type_symbols_after_checker ? {
        for t, s in b.table.type_symbols {
            println('> t: ${t:10} | s.mod: ${s.mod:-40} | s.name: ${'${s.name#[..30]}':-30} | s.is_builtin: ${s.is_builtin:6} | s.is_pub: ${s.is_pub}')
        }
    }

    if b.pref.new_generic_solver {
        util.timing_start('GENERICS')
        b.generics.solve_files(b.parsed_files)
        util.timing_start('Checker.generic_insts_to_concrete.after_generics')
        b.table.generic_insts_to_concrete()
        util.timing_measure('Checker.generic_insts_to_concrete.after_generics')
        util.timing_measure('GENERICS')
    }

    util.timing_start('COMPTIME')
    b.comptime.solve_files(b.parsed_files)
    util.timing_measure('COMPTIME')

    if b.pref.dump_defines != '' {
        b.dump_defines()
    }
    mut mcache := vmod.get_cache()
    mcache.debug()
    b.print_warnings_and_errors()
    if b.checker.should_abort {
        return error('too many errors/warnings/notices')
    }
    if b.checker.unresolved_fixed_sizes.len > 0 {
        util.timing_start('Checker.update_unresolved_fixed_sizes')
        b.checker.update_unresolved_fixed_sizes()
        util.timing_measure('Checker.update_unresolved_fixed_sizes')
    }
    if b.pref.check_only {
        return error_with_code('stop_after_checker', 8001)
    }
    util.timing_start('TRANSFORM')
    b.transformer.transform_files(b.parsed_files)
    util.timing_measure('TRANSFORM')

    b.table.complete_interface_check()
    if b.pref.skip_unused {
        markused.mark_used(mut b.table, mut b.pref, b.parsed_files)
    }
    if b.pref.show_callgraph {
        callgraph.show(mut b.table, b.pref, b.parsed_files)
    }
}

pub fn (mut b Builder) front_and_middle_stages(v_files []string) ! {
    b.front_stages(v_files)!
    b.middle_stages()!
}

@[inline]
fn (b &Builder) should_stop_after_frontend_error() bool {
    return b.pref.fatal_errors
        || (b.pref.output_mode == .stdout && !b.pref.check_only && !b.pref.is_vls)
}

@[inline]
fn (b &Builder) has_frontend_errors() bool {
    return b.parsed_files.any(it.errors.len > 0)
}

// parse all deps from already parsed files
pub fn (mut b Builder) parse_imports() {
    util.timing_start(@METHOD)
    defer {
        util.timing_measure(@METHOD)
    }
    mut done_imports := []string{}
    if b.pref.is_vsh {
        done_imports << 'os'
    }
    // TODO: (joe): decide if this is correct solution.
    // in the case of building a module, the actual module files
    // are passed via cmd line, so they have already been parsed
    // by this stage. note that if one files from a module was
    // parsed (but not all of them), then this will cause a problem.
    // we could add a list of parsed files instead, but I think
    // there is a better solution all around, I will revisit this.
    // NOTE: there is a very similar occurrence with the way
    // internal module test's work, and this was the reason there
    // were issues with duplicate declarations, so we should sort
    // that out in a similar way.
    for file in b.parsed_files {
        if file.mod.name != 'main' && file.mod.name !in done_imports {
            done_imports << file.mod.name
        }
    }
    // Note: b.parsed_files is appended in the loop,
    // so we can not use the shorter `for in` form.
    for i := 0; i < b.parsed_files.len; i++ {
        ast_file := b.parsed_files[i]
        append_map_array(mut b.path_invalidates_mods, ast_file.path, ast_file.mod.name)
        if ast_file.mod.name != 'builtin' {
            append_map_array(mut b.mod_invalidates_paths, 'builtin', ast_file.path)
            append_map_array(mut b.mod_invalidates_mods, 'builtin', ast_file.mod.name)
        }
        for imp in ast_file.imports {
            mod := imp.mod
            append_map_array(mut b.mod_invalidates_paths, mod, ast_file.path)
            append_map_array(mut b.mod_invalidates_mods, mod, ast_file.mod.name)
            if mod == 'builtin' {
                b.parsed_files[i].errors << b.error_with_pos('cannot import module "builtin"',
                    ast_file.path, imp.pos)
                break
            }
            if mod in done_imports {
                continue
            }
            import_path := b.find_module_path(mod, ast_file.path) or {
                // v.parsers[i].error_with_token_index('cannot import module "${mod}" (not found)', v.parsers[i].import_ast.get_import_tok_idx(mod))
                // break
                b.parsed_files[i].errors << b.error_with_pos('cannot import module "${mod}" (not found)',
                    ast_file.path, imp.pos)
                break
            }
            v_files := b.v_files_from_dir(import_path)
            if v_files.len == 0 {
                // v.parsers[i].error_with_token_index('cannot import module "${mod}" (no .v files in "${import_path}")', v.parsers[i].import_ast.get_import_tok_idx(mod))
                b.parsed_files[i].errors << b.error_with_pos('cannot import module "${mod}" (no .v files in "${import_path}")',
                    ast_file.path, imp.pos)
                continue
            }
            // eprintln('>> ast_file.path: ${ast_file.path} , done: ${done_imports}, `import ${mod}` => ${v_files}')
            // Add all imports referenced by these libs
            parsed_files := parser.parse_files(v_files, mut b.table, b.pref)
            for file in parsed_files {
                mut name := file.mod.name
                if name == '' {
                    name = file.mod.short_name
                }
                sname := name.all_after_last('.')
                smod := mod.all_after_last('.')
                if sname != smod {
                    msg := 'bad module definition: ${ast_file.path} imports module "${mod}" but ${file.path} is defined as module `${name}`'
                    b.parsed_files[i].errors << b.error_with_pos(msg, ast_file.path, imp.pos)
                }
            }
            b.parsed_files << parsed_files
            if b.should_stop_after_frontend_error() && parsed_files.any(it.errors.len > 0) {
                return
            }
            done_imports << mod
        }
    }
    b.resolve_deps()
    $if trace_parsed_files ? {
        b.show_parsed_files()
    }
    if b.pref.print_v_files {
        b.show_parsed_files()
        exit(0)
    }
    if b.pref.print_watched_files {
        for p in b.parsed_files {
            if p.is_parse_text {
                // a generated snippet, `v watch` does not care about those, since they are duplicates for other files
                continue
            }
            println(p.path)
            for tp in p.template_paths {
                println(tp)
            }
        }
        exit(0)
    }
    if b.pref.dump_files != '' {
        b.dump_files(b.parsed_files.map(it.path))
    }
    b.rebuild_modules()
}

pub fn (mut b Builder) resolve_deps() {
    util.timing_start(@METHOD)
    defer {
        util.timing_measure(@METHOD)
    }
    graph := b.import_graph()
    deps_resolved := graph.resolve()
    if b.pref.is_verbose {
        eprintln('------ resolved dependencies graph: ------')
        eprintln(deps_resolved.display())
        eprintln('------------------------------------------')
    }
    if b.pref.show_depgraph {
        depgraph.show(deps_resolved, b.pref.path)
    }
    cycles := deps_resolved.display_cycles()
    if cycles.len > 1 {
        verror('error: import cycle detected between the following modules: \n' + cycles)
    }
    mut mods := []string{}
    for node in deps_resolved.nodes {
        mods << node.name
    }
    b.dump_modules(mods)
    if b.pref.is_verbose {
        eprintln('------ imported modules: ------')
        eprintln(mods.str())
        eprintln('-------------------------------')
    }
    unsafe {
        mut reordered_parsed_files := []&ast.File{}
        for m in mods {
            for pf in b.parsed_files {
                if m == pf.mod.name {
                    reordered_parsed_files << pf
                    // eprintln('pf.mod.name: ${pf.mod.name} | pf.path: ${pf.path}')
                }
            }
        }
        b.table.modules = mods
        b.parsed_files = reordered_parsed_files
    }
}

fn import_alias_for_mod(file &ast.File, mod string) ?string {
    for import_m in file.imports {
        if import_m.mod == mod {
            return import_m.alias
        }
    }
    return none
}

fn register_used_import(mut file ast.File, alias string) {
    if alias !in file.used_imports {
        file.used_imports << alias
    }
}

fn file_needs_c_function_call_import_scan(file &ast.File) bool {
    for import_m in file.imports {
        alias := import_m.alias
        if (alias.len == 1 && alias[0] == `_`) || alias in file.used_imports
            || alias in file.auto_imports {
            continue
        }
        return true
    }
    return false
}

fn (mut b Builder) collect_used_c_function_calls(file &ast.File) map[string]bool {
    mut collector := CFunctionCallCollector{
        names: map[string]bool{}
    }
    walker.inspect(file, &collector, c_function_call_collector_visit)
    return collector.names
}

fn (mut b Builder) mark_imports_used_by_c_function_calls() {
    for mut file in b.parsed_files {
        if !file_needs_c_function_call_import_scan(file) {
            continue
        }
        used_c_calls := b.collect_used_c_function_calls(file)
        if used_c_calls.len == 0 {
            continue
        }
        for c_name, _ in used_c_calls {
            if c_fn := b.table.find_fn(c_name) {
                alias := import_alias_for_mod(file, c_fn.mod) or { continue }
                register_used_import(mut file, alias)
                continue
            }
            c_typ := b.table.find_type(c_name)
            if c_typ == 0 {
                continue
            }
            c_sym := b.table.sym(c_typ)
            if c_sym.kind == .placeholder {
                continue
            }
            alias := import_alias_for_mod(file, c_sym.mod) or { continue }
            register_used_import(mut file, alias)
        }
    }
}

fn (mut b Builder) add_unused_import_message(mut file ast.File, message string, pos token.Pos) {
    file_path := if pos.file_idx < 0 { file.path } else { b.table.filelist[pos.file_idx] }
    if b.pref.warns_are_errors {
        err := errors.Error{
            file_path: file_path
            pos:       pos
            reporter:  .parser
            message:   message
        }
        file.errors << err
        if b.pref.output_mode == .stdout && !b.pref.check_only {
            util.show_compiler_message('error:', err.CompilerMessage)
        }
        return
    }
    if b.pref.skip_warnings {
        return
    }
    wrn := errors.Warning{
        file_path: file_path
        pos:       pos
        reporter:  .parser
        message:   message
    }
    file.warnings << wrn
    if b.pref.output_mode == .stdout && !b.pref.check_only {
        util.show_compiler_message('warning:', wrn.CompilerMessage)
    }
}

fn (mut b Builder) check_unused_imports() {
    if b.pref.is_repl || b.pref.is_fmt {
        return
    }
    b.mark_imports_used_by_c_function_calls()
    for mut file in b.parsed_files {
        for import_m in file.imports {
            alias := import_m.alias
            mod := import_m.mod
            if (alias.len == 1 && alias[0] == `_`) || alias in file.used_imports
                || alias in file.auto_imports {
                continue
            }
            mod_alias := if alias == mod { alias } else { '${alias} (${mod})' }
            b.add_unused_import_message(mut file,
                "module '${mod_alias}' is imported but never used. Use `import ${mod_alias} as _`, to silence this warning, or just remove the unused import line",
                import_m.mod_pos)
        }
    }
}

// graph of all imported modules
pub fn (b &Builder) import_graph() &depgraph.DepGraph {
    builtins := util.builtin_module_parts.clone()
    mut graph := depgraph.new_dep_graph()
    for p in b.parsed_files {
        // eprintln('p.path: ${p.path}')
        mut deps := []string{}
        if p.mod.name !in builtins {
            deps << 'builtin'
            if b.pref.backend == .c {
                // TODO: JavaScript backend doesn't handle os for now
                // os import libraries so we exclude anything which could cause a loop
                if p.path.ends_with('.vsh') {
                    deps << 'os'
                }
            }
        }
        for m in p.imports {
            if m.mod == p.mod.name {
                continue
            }
            deps << m.mod
        }
        graph.add(p.mod.name, deps)
    }
    $if trace_import_graph ? {
        eprintln(graph.display())
    }
    return graph
}

pub fn (b &Builder) v_files_from_dir(dir string) []string {
    if !os.exists(dir) {
        if dir == 'compiler' && os.is_dir('vlib') {
            println('looks like you are trying to build V with an old command')
            println('use `v -o v cmd/v` instead of `v -o v compiler`')
        }
        verror("${dir} doesn't exist")
    } else if !os.is_dir(dir) {
        verror("${dir} isn't a directory!")
    }
    mut files := os.ls(dir) or { panic(err) }
    mut source_dir := os.real_path(dir)
    if b.pref.is_verbose {
        println('v_files_from_dir ("${dir}")')
    }
    mut res := b.pref.should_compile_filtered_files(dir, files)
    if res.len == 0 {
        // An explicit `base_url` in v.mod still re-homes the source folder.
        if source_root := source_root_from_vmod_root(dir) {
            if source_root != dir && os.is_dir(source_root) {
                if b.pref.is_verbose {
                    println('v_files_from_dir ("${source_root}") (v.mod base_url)')
                }
                files = os.ls(source_root) or { panic(err) }
                source_dir = os.real_path(source_root)
                res = b.pref.should_compile_filtered_files(source_root, files)
            }
        }
        if res.len == 0 {
            report_removed_src_layout_if_any(dir)
        }
    }
    return b.with_same_module_subdir_files(source_dir, res)
}

// report_removed_src_layout_if_any prints a clear error if `dir` still relies on
// the removed virtual `src/` module layout (sources under `dir/src/` instead of
// at the module root). The explicit `base_url` opt-in in v.mod is unaffected.
fn report_removed_src_layout_if_any(dir string) {
    src_dir := os.join_path(dir, 'src')
    if !os.is_dir(src_dir) {
        return
    }
    src_files := os.ls(src_dir) or { return }
    mut has_v_files := false
    for f in src_files {
        if f.ends_with('.v') {
            has_v_files = true
            break
        }
    }
    if !has_v_files {
        return
    }
    verror('the virtual `src/` module directory is no longer supported.\nV found .v source files under ${src_dir}, but will not treat `src/` as a virtual module root anymore.\nPlease move the sources up from `src/` into ${dir}:\n\tmv ${src_dir}/*.v ${dir}/\n\trmdir ${src_dir}\n\nIf you want to split one module across subdirectories after moving the root files, add `subdirs` to v.mod, for example:\n\tsubdirs: [\'admin\', \'repo\', \'commit\', \'ci\', \'security\', \'ssh\', \'user\']')
}

fn (b &Builder) with_same_module_subdir_files(source_dir string, v_files []string) []string {
    mut mcache := vmod.get_cache()
    vmod_file_location := mcache.get_by_folder(source_dir)
    if vmod_file_location.vmod_file == '' {
        return v_files
    }
    module_source_root := b.module_source_root(vmod_file_location.vmod_folder)
    if source_dir != module_source_root {
        return v_files
    }
    manifest := vmod.from_file(vmod_file_location.vmod_file) or { return v_files }
    subdirs := manifest.unknown['subdirs'] or { return v_files }
    if subdirs.len == 0 {
        return v_files
    }
    mut res := v_files.clone()
    mut seen := map[string]bool{}
    for file in res {
        seen[os.real_path(file)] = true
    }
    for subdir in subdirs {
        normalized_subdir := normalize_same_module_subdir(subdir, manifest.base_url) or { continue }
        subdir_path := os.join_path(module_source_root, normalized_subdir)
        b.collect_same_module_v_files(vmod_file_location.vmod_folder, subdir_path, mut seen, mut
            res)
    }
    return res
}

fn (b &Builder) module_source_root(module_root string) string {
    real_module_root := os.real_path(module_root)
    if source_root := source_root_from_vmod_root(real_module_root) {
        if source_root != real_module_root && os.is_dir(source_root) {
            return os.real_path(source_root)
        }
    }
    return real_module_root
}

fn normalize_same_module_subdir(subdir string, base_url string) !string {
    mut normalized := os.norm_path(subdir.trim_space().replace('\\', os.path_separator).replace('/',
        os.path_separator))
    if normalized == '' || normalized == '.' || os.is_abs_path(normalized) {
        return error('invalid subdir')
    }
    if base_url != '' {
        base := os.norm_path(base_url).trim_left(os.path_separator).trim_right(os.path_separator)
        if base != '' {
            base_prefix := base + os.path_separator
            if normalized == base {
                return error('invalid subdir')
            }
            if normalized.starts_with(base_prefix) {
                normalized = normalized.all_after(base_prefix)
            }
        }
    }
    normalized = normalized.trim_left(os.path_separator).trim_right(os.path_separator)
    if normalized == '' {
        return error('invalid subdir')
    }
    parts := normalized.split(os.path_separator)
    if '' in parts || '.' in parts || '..' in parts {
        return error('invalid subdir')
    }
    return normalized
}

fn (b &Builder) collect_same_module_v_files(module_root string, dir string, mut seen map[string]bool, mut res []string) {
    if !os.is_dir(dir) {
        return
    }
    real_dir := os.real_path(dir)
    if real_dir != os.real_path(module_root) && os.is_file(os.join_path(real_dir, 'v.mod')) {
        return
    }
    mut entries := os.ls(real_dir) or { return }
    entries.sort()
    for file in b.pref.should_compile_filtered_files(real_dir, entries) {
        real_file := os.real_path(file)
        if real_file !in seen {
            seen[real_file] = true
            res << file
        }
    }
    for entry in entries {
        subdir_path := os.join_path(real_dir, entry)
        if os.is_dir(subdir_path) {
            b.collect_same_module_v_files(module_root, subdir_path, mut seen, mut res)
        }
    }
}

pub fn (b &Builder) log(s string) {
    if b.pref.is_verbose {
        println(s)
    }
}

pub fn (b &Builder) info(s string) {
    if b.pref.is_verbose {
        println(s)
    }
}

@[inline]
pub fn module_path(mod string) string {
    // submodule support
    return mod.replace('.', os.path_separator)
}

fn manifest_from_vmod_root(vmod_root string) !vmod.Manifest {
    vmod_path := os.join_path(vmod_root, 'v.mod')
    if !os.is_file(vmod_path) {
        return error('module not found')
    }
    return vmod.from_file(vmod_path) or { return error('module not found') }
}

fn source_root_from_vmod_root(vmod_root string) !string {
    manifest := manifest_from_vmod_root(vmod_root)!
    if manifest.base_url == '' {
        return error('module not found')
    }
    return manifest.source_root(vmod_root)
}

fn find_module_path_from_vmod_root(vmod_root string, mod string) !string {
    manifest := manifest_from_vmod_root(vmod_root)!
    if manifest.base_url == '' {
        return error('module not found')
    }
    tail_path := mod_tail_after_vmod_name(mod, manifest.name) or {
        return error('module not found')
    }
    if tail_path == '' {
        return error('module not found')
    }
    try_path := os.join_path(manifest.source_root(vmod_root), tail_path)
    if os.is_dir(try_path) {
        return try_path
    }
    return error('module not found')
}

fn find_module_path_from_search_root(search_path string, mod string) !string {
    mod_path := module_path(mod)
    try_path := os.join_path_single(search_path, mod_path)
    if os.is_dir(try_path) {
        return try_path
    }
    if src_try_path := find_module_path_from_vmod_root(search_path, mod) {
        return src_try_path
    }
    mod_parts := mod.split('.')
    for i := mod_parts.len - 1; i > 0; i-- {
        candidate_root := os.join_path_single(search_path, mod_parts[..i].join(os.path_separator))
        if !os.is_file(os.join_path(candidate_root, 'v.mod')) {
            continue
        }
        source_root := source_root_from_vmod_root(candidate_root) or { continue }
        submodule_path := mod_parts[i..].join(os.path_separator)
        src_try_path := os.join_path(source_root, submodule_path)
        if os.is_dir(src_try_path) {
            return src_try_path
        }
    }
    return error('module not found')
}

fn mod_tail_after_vmod_name(mod string, vmod_name string) !string {
    if vmod_name == '' {
        return error('module not found')
    }
    mod_parts := mod.split('.')
    vmod_parts := vmod_name.split('.')
    for i := 0; i + vmod_parts.len <= mod_parts.len; i++ {
        if i > 1 {
            break
        }
        if mod_parts[i..i + vmod_parts.len].join('.') == vmod_name {
            return mod_parts[i + vmod_parts.len..].join(os.path_separator)
        }
    }
    return error('module not found')
}

fn (b &Builder) module_path_has_v_files(path string) bool {
    return b.v_files_from_dir(path).len > 0
}

// TODO: try to merge this & util.module functions to create a
// reliable multi use function. see comments in util/module.v
pub fn (b &Builder) find_module_path(mod string, fpath string) !string {
    // support @VEXEROOT/v.mod relative paths:
    mut mcache := vmod.get_cache()
    resolved_fpath := os.real_path(fpath)
    vmod_file_location := mcache.get_by_file(resolved_fpath)
    mod_path := module_path(mod)
    mut module_lookup_paths := []string{}
    if vmod_file_location.vmod_file.len != 0
        && vmod_file_location.vmod_folder !in b.module_search_paths {
        module_lookup_paths << vmod_file_location.vmod_folder
    }
    module_lookup_paths << b.module_search_paths
    // go up through parents looking for modules a folder.
    // we need a proper solution that works most of the time. look at vdoc.get_parent_mod
    if resolved_fpath.contains(os.path_separator + 'modules' + os.path_separator) {
        parts := resolved_fpath.split(os.path_separator)
        for i := parts.len - 2; i >= 0; i-- {
            if parts[i] == 'modules' {
                module_lookup_paths << parts[0..i + 1].join(os.path_separator)
                break
            }
        }
    }
    mut empty_module_path := ''
    for search_path in module_lookup_paths {
        try_path := os.join_path(search_path, mod_path)
        if b.pref.is_verbose {
            println('  >> trying to find ${mod} in ${try_path} ..')
        }
        if found_path := find_module_path_from_search_root(search_path, mod) {
            if b.module_path_has_v_files(found_path) {
                if b.pref.is_verbose {
                    println('  << found ${found_path} .')
                }
                return found_path
            }
            if empty_module_path == '' {
                empty_module_path = found_path
            }
            if b.pref.is_verbose {
                println('  << skipped ${found_path} (no .v files) .')
            }
        }
    }
    // look up through parents
    mut current_dir := os.dir(resolved_fpath)
    for {
        try_path := os.join_path(current_dir, mod_path)
        if b.pref.is_verbose {
            println('  >> trying to find ${mod} in ${try_path} ..')
        }
        if found_path := find_module_path_from_search_root(current_dir, mod) {
            if b.module_path_has_v_files(found_path) {
                if b.pref.is_verbose {
                    println('  << found ${found_path} .')
                }
                return found_path
            }
            if empty_module_path == '' {
                empty_module_path = found_path
            }
            if b.pref.is_verbose {
                println('  << skipped ${found_path} (no .v files) .')
            }
        }
        parent_dir := os.dir(current_dir)
        if parent_dir == current_dir {
            break
        }
        current_dir = parent_dir
    }
    if empty_module_path != '' {
        return empty_module_path
    }
    smodule_lookup_paths := module_lookup_paths.join(', ')
    return error('module "${mod}" not found in:\n${smodule_lookup_paths}')
}

pub fn (b &Builder) show_total_warns_and_errors_stats() {
    if b.nr_errors == 0 && b.nr_warnings == 0 && b.nr_notices == 0 {
        return
    }
    if b.pref.is_stats {
        mut nr_errors := b.checker.nr_errors
        mut nr_warnings := b.checker.nr_warnings
        mut nr_notices := b.checker.nr_notices

        if b.pref.check_only {
            nr_errors = b.nr_errors
            nr_warnings = b.nr_warnings
            nr_notices = b.nr_notices
        }

        estring := util.bold(nr_errors.str())
        wstring := util.bold(nr_warnings.str())
        nstring := util.bold(nr_notices.str())

        if b.pref.check_only {
            println('summary: ${estring} V errors, ${wstring} V warnings, ${nstring} V notices')
        } else {
            println('checker summary: ${estring} V errors, ${wstring} V warnings, ${nstring} V notices')
        }
    }
    if !b.pref.is_vls && b.checker.nr_errors > 0 && b.pref.path.ends_with('.v')
        && os.is_file(b.pref.path) && !b.pref.path.ends_with('vrepl_temp.v') {
        if b.checker.errors.any(it.message.starts_with('unknown ')) {
            // Sometimes users try to `v main.v`, when they have several .v files in their project.
            // Then, they encounter puzzling errors about missing or unknown types. In this case,
            // the intended command may have been `v .` instead, so just suggest that:
            old_cmd := util.bold('v ${b.pref.path}')
            new_cmd := util.bold('v ${os.dir(b.pref.path)}')
            eprintln(util.color('notice',
                'If the code of your project is in a folder with multiple .v files, try `${new_cmd}` instead of `${old_cmd}`'))
        }
    }
}

pub fn (mut b Builder) print_warnings_and_errors() {
    defer {
        b.show_total_warns_and_errors_stats()
    }

    for file in b.parsed_files {
        b.nr_errors += file.errors.len
        b.nr_warnings += file.warnings.len
        b.nr_notices += file.notices.len
    }

    if b.pref.output_mode == .silent {
        if b.nr_errors > 0 {
            exit(1)
        }
        return
    }

    if b.pref.check_only {
        if !b.pref.skip_notes && !b.pref.json_errors {
            for file in b.parsed_files {
                for err in file.notices {
                    kind := if b.pref.is_verbose {
                        '${err.reporter} notice #${b.nr_notices}:'
                    } else {
                        'notice:'
                    }
                    util.show_compiler_message(kind, err.CompilerMessage)
                }
            }
        }

        mut json_errors := []util.JsonError{}
        for file in b.parsed_files {
            for err in file.errors {
                kind := if b.pref.is_verbose {
                    '${err.reporter} error #${b.nr_errors}:'
                } else {
                    'error:'
                }

                if b.pref.json_errors {
                    json_errors << util.JsonError{
                        message: err.message
                        path:    os.to_slash(err.file_path)
                        line_nr: err.pos.line_nr + 1
                        col:     err.pos.col + 1
                    }
                    // util.print_json_error(kind, err.CompilerMessage)
                } else {
                    util.show_compiler_message(kind, err.CompilerMessage)
                }
            }
        }
        if b.pref.json_errors {
            if !b.pref.is_vls
                || b.pref.linfo.method !in [.definition, .completion, .signature_help, .hover] {
                util.print_json_errors(json_errors)
            }
            // eprintln(json2.encode_pretty(json_errors))
        }
        if !b.pref.skip_warnings {
            for file in b.parsed_files {
                for err in file.warnings {
                    kind := if b.pref.is_verbose {
                        '${err.reporter} warning #${b.nr_warnings}:'
                    } else {
                        'warning:'
                    }
                    util.show_compiler_message(kind, err.CompilerMessage)
                }
            }
        }

        b.show_total_warns_and_errors_stats()
        if b.nr_errors > 0 {
            exit(1)
        }
    }

    if b.pref.is_verbose && b.checker.nr_warnings > 1 {
        println('${b.checker.nr_warnings} warnings')
    }
    if b.pref.is_verbose && b.checker.nr_notices > 1 {
        println('${b.checker.nr_notices} notices')
    }
    if b.checker.nr_notices > 0 && !b.pref.skip_notes {
        for err in b.checker.notices {
            kind := if b.pref.is_verbose {
                '${err.reporter} notice #${b.checker.nr_notices}:'
            } else {
                'notice:'
            }
            util.show_compiler_message(kind, err.CompilerMessage)
        }
    }
    if b.checker.nr_warnings > 0 && !b.pref.skip_warnings {
        for err in b.checker.warnings {
            kind := if b.pref.is_verbose {
                '${err.reporter} warning #${b.checker.nr_warnings}:'
            } else {
                'warning:'
            }
            util.show_compiler_message(kind, err.CompilerMessage)
        }
    }

    if b.pref.is_verbose && b.checker.nr_errors > 1 {
        println('${b.checker.nr_errors} errors')
    }
    if b.checker.nr_errors > 0 {
        for err in b.checker.errors {
            kind := if b.pref.is_verbose {
                '${err.reporter} error #${b.checker.nr_errors}:'
            } else {
                'error:'
            }
            util.show_compiler_message(kind, err.CompilerMessage)
        }
        b.show_total_warns_and_errors_stats()
        exit(1)
    }
    if b.table.redefined_fns.len > 0 {
        mut total_conflicts := 0
        for fn_name in b.table.redefined_fns {
            // Find where this function was already declared
            mut redefines := []FunctionRedefinition{}
            mut redefine_conflicts := map[string]int{}
            for file in b.parsed_files {
                for stmt in file.stmts {
                    if stmt is ast.FnDecl {
                        if stmt.name == fn_name {
                            fheader := b.table.stringify_fn_decl(&stmt, 'main',
                                map[string]string{}, false)
                            redefines << FunctionRedefinition{
                                fpath:   file.path
                                fline:   stmt.pos.line_nr
                                f:       stmt
                                fheader: fheader
                            }
                            redefine_conflicts[fheader]++
                        }
                    }
                }
            }
            if redefines.len > 0 {
                util.show_compiler_message('builder error:',
                    message: 'redefinition of function `${fn_name}`'
                )
                for redefine in redefines {
                    util.show_compiler_message('conflicting declaration:',
                        message:   redefine.fheader
                        file_path: redefine.fpath
                        pos:       redefine.f.pos
                    )
                }
                total_conflicts++
            }
        }
        if total_conflicts > 0 {
            b.show_total_warns_and_errors_stats()
            exit(1)
        }
    }
}

struct FunctionRedefinition {
    fpath   string
    fline   int
    fheader string
    f       ast.FnDecl
}

pub fn (b &Builder) error_with_pos(s string, fpath string, pos token.Pos) errors.Error {
    return errors.Error{
        file_path: fpath
        pos:       pos
        reporter:  .builder
        message:   s
    }
}

fn (b &Builder) print_frontend_builder_errors() {
    if b.pref.check_only || b.pref.output_mode != .stdout {
        return
    }
    for file in b.parsed_files {
        for err in file.errors {
            if err.reporter == .builder {
                util.show_compiler_message('builder error:', err.CompilerMessage)
            }
        }
    }
}

@[noreturn]
pub fn verror(s string) {
    util.verror('builder error', s)
}

pub fn (mut b Builder) show_parsed_files() {
    for p in b.parsed_files {
        if p.is_parse_text {
            println(p.path + ':parse_text')
        }
        println(p.path)
    }
}