// Copyright (c) 2020-2024 Joe Conigliaro. 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

fn (p &Preferences) effective_vroot() string {
    if p.vroot.len > 0 {
        return p.vroot
    }
    return os.getwd()
}

pub fn (p &Preferences) get_vlib_module_path(mod string) string {
    mod_path := mod.replace('.', os.path_separator)
    return module_path_join(module_path_join(p.effective_vroot(), 'vlib'), mod_path)
}

fn module_path_join(base string, name string) string {
    if base.len == 0 {
        return name
    }
    if name.len == 0 {
        return base
    }
    last := base[base.len - 1]
    if last == `/` || last == `\\` {
        return base + name
    }
    return base + os.path_separator + name
}

fn module_root_for_file(path string) string {
    mut dir := os.dir(path)
    for dir.len > 0 {
        if os.exists(module_path_join(dir, 'v.mod')) {
            return dir
        }
        parent := os.dir(dir)
        if parent == dir {
            break
        }
        dir = parent
    }
    return ''
}

fn find_module_path_in_parent_dirs(mod_path string, importing_file_path string) ?string {
    mut dir := os.dir(importing_file_path)
    for dir.len > 0 {
        parent_relative_path := module_path_join(dir, mod_path)
        if dir_exists(parent_relative_path) {
            return parent_relative_path
        }
        parent := os.dir(dir)
        if parent == dir {
            break
        }
        dir = parent
    }
    return none
}

// check for relative and then vlib
pub fn (p &Preferences) get_module_path(mod string, importing_file_path string) string {
    mod_path := mod.replace('.', os.path_separator)
    vroot := p.effective_vroot()
    // relative to file importing it
    relative_path := module_path_join(os.dir(importing_file_path), mod_path)
    if dir_exists(relative_path) {
        return relative_path
    }
    module_root := module_root_for_file(importing_file_path)
    if module_root != '' {
        root_relative_path := module_path_join(module_root, mod_path)
        if dir_exists(root_relative_path) {
            return root_relative_path
        }
    }
    if parent_relative_path := find_module_path_in_parent_dirs(mod_path, importing_file_path) {
        return parent_relative_path
    }
    cwd_relative_path := module_path_join(os.getwd(), mod_path)
    if dir_exists(cwd_relative_path) {
        return cwd_relative_path
    }
    // TODO: is this the best order?
    // vlib
    vlib_path := module_path_join(module_path_join(vroot, 'vlib'), mod_path)
    if dir_exists(vlib_path) {
        return vlib_path
    }
    // V1 compiler modules under vlib/v use legacy bare sibling imports
    // (`import token` from vlib/v/checker, with sources in vlib/v/token).
    vlib_v_path := module_path_join(module_path_join(vroot, 'vlib'), 'v')
    normalized_importer := importing_file_path.replace('\\', '/')
    normalized_vlib_v := vlib_v_path.replace('\\', '/')
    if normalized_importer.starts_with(normalized_vlib_v + '/')
        || normalized_importer.starts_with('vlib/v/') {
        legacy_v_path := module_path_join(vlib_v_path, mod_path)
        if dir_exists(legacy_v_path) {
            return legacy_v_path
        }
    }
    // ~/.vmodules
    vmodules_path := module_path_join(p.vmodules_path, mod_path)
    if dir_exists(vmodules_path) {
        // V convention: if a module dir has a src/ subdirectory, use that
        src_path := module_path_join(vmodules_path, 'src')
        if dir_exists(src_path) {
            return src_path
        }
        return vmodules_path
    }
    panic('Preferences.get_module_path: cannot find module path for `${mod}`')
}