<?php

namespace SilverStripe\View;

use SilverStripe\Core\Manifest\ModuleLoader;

/**
 * Handles finding templates from a stack of template manifest objects.
 */
class ThemeResourceLoader
{

    /**
     * @var ThemeResourceLoader
     */
    private static $instance;

    protected $base;

    /**
     * List of template "sets" that contain a test manifest, and have an alias.
     * E.g. '$default'
     *
     * @var ThemeList[]
     */
    protected $sets = [];

    /**
     * @return ThemeResourceLoader
     */
    public static function inst()
    {
        return self::$instance ? self::$instance : self::$instance = new self();
    }

    /**
     * Set instance
     *
     * @param ThemeResourceLoader $instance
     */
    public static function set_instance(ThemeResourceLoader $instance)
    {
        self::$instance = $instance;
    }

    public function __construct($base = null)
    {
        $this->base = $base ? $base : BASE_PATH;
    }

    /**
     * Add a new theme manifest for a given identifier. E.g. '$default'
     *
     * @param string $set
     * @param ThemeList $manifest
     */
    public function addSet($set, ThemeList $manifest)
    {
        $this->sets[$set] = $manifest;
    }

    /**
     * Get a named theme set
     *
     * @param string $set
     * @return ThemeList
     */
    public function getSet($set)
    {
        if (isset($this->sets[$set])) {
            return $this->sets[$set];
        }
        return null;
    }

    /**
     * Given a theme identifier, determine the path from the root directory
     *
     * The mapping from $identifier to path follows these rules:
     * - A simple theme name ('mytheme') which maps to the standard themes dir (/themes/mytheme)
     * - A theme path with a leading slash ('/mymodule/themes/mytheme') which maps directly to that path.
     * - or a vendored theme path. (vendor/mymodule:mytheme) which maps to the nested 'theme' within
     *   that module. ('/mymodule/themes/mytheme').
     * - A vendored module with no nested theme (vendor/mymodule) which maps to the root directory
     *   of that module. ('/mymodule').
     *
     * @param string $identifier Theme identifier.
     * @return string Path from root, not including leading or trailing forward slash. E.g. themes/mytheme
     */
    public function getPath($identifier)
    {
        $slashPos = strpos($identifier, '/');

        // If identifier starts with "/", it's a path from root
        if ($slashPos === 0) {
            return substr($identifier, 1);
        } // Otherwise if there is a "/", identifier is a vendor'ed module
        elseif ($slashPos !== false) {
            // Extract from <vendor>/<module>:<theme> format.
            // <vendor> is optional, and if <theme> is omitted it defaults to the module root dir.
            // If <theme> is included, this is the name of the directory under moduleroot/themes/
            // which contains the theme.
            // <module> is always the name of the install directory, not necessarily the composer name.
            $parts = explode(':', $identifier, 2);

            if (count($parts) > 1) {
                $theme = $parts[1];
                // "module/vendor:/sub/path"
                if ($theme[0] === '/') {
                    $subpath = $theme;

                // "module/vendor:subtheme"
                } else {
                    $subpath = '/themes/' . $theme;
                }

            // "module/vendor"
            } else {
                $subpath = '';
            }

            $package = $parts[0];

            // Find matching module for this package
            $module = ModuleLoader::inst()->getManifest()->getModule($package);
            if ($module) {
                $modulePath = $module->getRelativePath();
            } else {
                // fall back to dirname
                list(, $modulePath) = explode('/', $parts[0], 2);

                // If the module is in the themes/<module>/ prefer that
                if (is_dir(THEMES_PATH . '/' .$modulePath)) {
                    $modulePath = THEMES_DIR . '/' . $$modulePath;
                }
            }

            return ltrim($modulePath . $subpath, '/');
        } // Otherwise it's a (deprecated) old-style "theme" identifier
        else {
            return THEMES_DIR.'/'.$identifier;
        }
    }

    /**
     * Attempts to find possible candidate templates from a set of template
     * names from modules, current theme directory and finally the application
     * folder.
     *
     * The template names can be passed in as plain strings, or be in the
     * format "type/name", where type is the type of template to search for
     * (e.g. Includes, Layout).
     *
     * @param string|array $template Template name, or template spec in array format with the keys
     * 'type' (type string) and 'templates' (template hierarchy in order of precedence).
     * If 'templates' is ommitted then any other item in the array will be treated as the template
     * list, or list of templates each in the array spec given.
     * Templates with an .ss extension will be treated as file paths, and will bypass
     * theme-coupled resolution.
     * @param array $themes List of themes to use to resolve themes. In most cases
     * you should pass in {@see SSViewer::get_themes()}
     * @return string Absolute path to resolved template file, or null if not resolved.
     * File location will be in the format themes/<theme>/templates/<directories>/<type>/<basename>.ss
     * Note that type (e.g. 'Layout') is not the root level directory under 'templates'.
     */
    public function findTemplate($template, $themes)
    {
        $type = '';
        if (is_array($template)) {
            // Check if templates has type specified
            if (array_key_exists('type', $template)) {
                $type = $template['type'];
                unset($template['type']);
            }
            // Templates are either nested in 'templates' or just the rest of the list
            $templateList = array_key_exists('templates', $template) ? $template['templates'] : $template;
        } else {
            $templateList = array($template);
        }

        foreach ($templateList as $i => $template) {
            // Check if passed list of templates in array format
            if (is_array($template)) {
                $path = $this->findTemplate($template, $themes);
                if ($path) {
                    return $path;
                }
                continue;
            }

            // If we have an .ss extension, this is a path, not a template name. We should
            // pass in templates without extensions in order for template manifest to find
            // files dynamically.
            if (substr($template, -3) == '.ss' && file_exists($template)) {
                return $template;
            }

            // Check string template identifier
            $template = str_replace('\\', '/', $template);
            $parts = explode('/', $template);

            $tail = array_pop($parts);
            $head = implode('/', $parts);

            $themePaths = $this->getThemePaths($themes);
            foreach ($themePaths as $themePath) {
                // Join path
                $pathParts = [ $this->base, $themePath, 'templates', $head, $type, $tail ];
                $path = implode('/', array_filter($pathParts)) . '.ss';
                if (file_exists($path)) {
                    return $path;
                }
            }
        }

        // No template found
        return null;
    }

    /**
     * Resolve themed CSS path
     *
     * @param string $name Name of CSS file without extension
     * @param array $themes List of themes
     * @return string Path to resolved CSS file (relative to base dir)
     */
    public function findThemedCSS($name, $themes)
    {
        if (substr($name, -4) !== '.css') {
            $name .= '.css';
        }

        $filename = $this->findThemedResource("css/$name", $themes);
        if ($filename === null) {
            $filename = $this->findThemedResource($name, $themes);
        }

        return $filename;
    }

    /**
     * Resolve themed javascript path
     *
     * A javascript file in the current theme path name 'themename/javascript/$name.js' is first searched for,
     * and it that doesn't exist and the module parameter is set then a javascript file with that name in
     * the module is used.
     *
     * @param string $name The name of the file - eg '/js/File.js' would have the name 'File'
     * @param array $themes List of themes
     * @return string Path to resolved javascript file (relative to base dir)
     */
    public function findThemedJavascript($name, $themes)
    {
        if (substr($name, -3) !== '.js') {
            $name .= '.js';
        }

        $filename = $this->findThemedResource("javascript/$name", $themes);
        if ($filename === null) {
            $filename = $this->findThemedResource($name, $themes);
        }

        return $filename;
    }

    /**
     * Resolve a themed resource
     *
     * A themed resource and be any file that resides in a theme folder.
     *
     * @param string $resource A file path relative to the root folder of a theme
     * @param array $themes An order listed of themes to search
     */
    public function findThemedResource($resource, $themes)
    {
        if ($resource[0] !== '/') {
            $resource = '/' . $resource;
        }

        $paths = $this->getThemePaths($themes);

        foreach ($paths as $themePath) {
            $abspath = $this->base . '/' . $themePath;
            if (file_exists($abspath . $resource)) {
                return $themePath . $resource;
            }
        }

        // Resource exists in no context
        return null;
    }

    /**
     * Resolve all themes to the list of root folders relative to site root
     *
     * @param array $themes List of themes to resolve. Supports named theme sets.
     * @return array List of root-relative folders in order of precendence.
     */
    public function getThemePaths($themes)
    {
        $paths = [];
        foreach ($themes as $themename) {
            // Expand theme sets
            $set = $this->getSet($themename);
            $subthemes = $set ? $set->getThemes() : [$themename];

            // Resolve paths
            foreach ($subthemes as $theme) {
                $paths[] = $this->getPath($theme);
            }
        }
        return $paths;
    }
}