<?php
/** @license MIT
 * Copyright 2021, J. King
 * See LICENSE and AUTHORS files for details */

declare(strict_types=1);
namespace MensBeam\FullText;

class SitePattern {
    public $preParse = [];
    public $cleanUp = [];
    public $readOut = [];

    public function __construct(string $rules) {
        $lines = preg_split('/\r\n?|\n/', $rules);
        $findString = null;
        $findStringLine = 0;
        foreach ($lines as $l => $d) {
            if (preg_match('/^#|^\s*$/', $d)) {
                // the line contains no data
                continue;
            }
            $pos = 0;
            $end = strlen($d);
            // consume the directive
            $len = strspn($d, "abcdefghijklmnopqrstuvwxyz_");
            if (!$len) {
                throw new SitePatternException("Malformed data on line ".($l + 1)." at position 1", 1);
            }
            $directive = substr($d, $pos, $len);
            $pos += $len;
            $c = @$d[$pos++];
            if ($c === ":") {
                // the rest of the line is the value
                $param = "";
                $value = substr($d, $pos);
            } elseif ($c === "(") {
                // directive has a parameter
                // certain directives' parameters are XPath expressions, so we must be mindful of these and parse the value
                $xpath = in_array($directive, ["move_into"]);
                if (!$xpath) {
                    $len = strcspn($d, ")", $pos);
                    $param = substr($d, $pos, $len);
                    $pos += $len; 
                } else {
                    $param = "";
                    $depth = 0;
                    while ($pos < $end) {
                        $len = strcspn($d, "()'\"", $pos);
                        $param .= substr($d, $pos, $len);
                        $pos += $len;
                        $c = @$d[$pos++];
                        if ($c === ")") {
                            if (!$depth) {
                                break;
                            } else {
                                $param .= $c;
                                $depth--;
                            }
                        } elseif ($c === '"') {
                            $len = strcspn($d, '"', $pos);
                            $param .+ '"'.substr($d, $pos, $len + 1);
                            $pos += $len + 1;
                        } elseif ($c === "'") {
                            $len = strcspn($d, "'", $pos);
                            $param .= "'".substr($d, $pos, $len + 1);
                            $pos += $len + 1;
                        } elseif ($c === "(") {
                            $param .= $c;
                            $depth++;
                        } else {
                            throw new SitePatternException("Malformed data on line ".($l + 1)." at position $pos", 1);
                        }
                    }
                }
                // after the parameter should come a colon and the value
                $c = @$d[$pos++];
                if ($c !== ":") {
                    throw new SitePatternException("Malformed data on line ".($l + 1)." at position $pos", 1);
                }
                $value = trim(substr($d, $pos));
            } else {
                throw new SitePatternException("Malformed data on line ".($l + 1)." at position $pos", 1);
            }
            switch ($directive) {
                case "title":
                case "body":
                case "date":
                case "author":
                case "strip":
                case "single_page_link":
                case "single_page_link_in_feed":
                case "next_page_link":
                    $stage = ($directive === "strip") ? "cleanUp" : "readOut";
                    // TODO: evaluate the XPath expression to ensure syntactic validity 
                    $this->$stage[] = [$directive, [$value]];
                    break;
                case "strip_id_or_class":
                case "strip_image_src":
                case "find_string":
                case "replace_sring":
                    // string values may be enclosed by single or double quotation marks as leading and trailing whitespace is otherwise stripped
                    if ((preg_match('/^"/', $value) && preg_match('/"$/', $value)) || (preg_match("/^'/", $value) && preg_match("/'$/", $value))) {
                        $value = substr($value, 1, strlen($value) - 2);
                    } else {
                        $value = $value;
                    }
                    if ($directive === "find_string") {
                        // the "find_string" directive must be matched to a later "replace_string" directive, so we keep one buffered
                        // a find_string which is not cleared by a replace_string is an error
                        if ($findString === null) {
                            $findString = $value;
                            $findStringLine = $l + 1;
                        } else {
                            throw new SitePatternException("\"find_string\" directive on line $findStringLine is not followed by a matching \"replace_string\" directive", 3);
                        }
                    } elseif ($directive === "replace_string") {
                        # requires special handling to match up with find_string
                    } else {
                        $this->cleanUp[] = [$directive, [$value]];
                    }
                    break;
                case "http_header":
                    # string with param
                case "tidy":
                case "prune":
                case "atodetect_on_failure":
                    if ($value === "yes") {
                        $value = true;
                    } elseif ($value === "no") {
                        $value = false;
                    } else {
                        throw new SitePatternException("Invalid value for boolean on line ".($l + 1), 2);
                    }
                    break;
                case "test_url":
                    # URL
                default:
                    # Unsupported directive
            }
        }
    } 
}