<?php namespace SokoWeb\View;

class Parser
{
    private string $file;

    public function __construct(string $file)
    {
        $this->file = $file;
    }

    public function parse(): ParsedFragment
    {
        $sectionOpen = null;
        $extraOpen = false;

        $extends = null;
        $js = [];
        $css = [];
        $sections = [];
        $extra = ['', ''];

        $fileHandle = fopen($this->file, 'r');
        if (!$fileHandle) {
            throw new \Exception('Cannot open file ' . $this->file);
        }

        $lineNumber = 0;
        while (($line = fgets($fileHandle)) !== false) {
            ++$lineNumber;

            if (($cssMatched = $this->matchCss($line)) !== null) {
                $css[] = $cssMatched;

                continue;
            }

            if (($jsMatched = $this->matchJs($line)) !== null) {
                $js[] = $jsMatched;

                continue;
            }

            if (($extendsMatched = $this->matchExtends($line)) !== null) {
                if ($extends !== null) {
                    throw new \Exception('Error in file ' . $this->file . ' in line ' . $lineNumber . ' - There is already an \'@extends\' declared.');
                }

                $extends = $extendsMatched;

                continue;
            }

            if (($sectionMatched = $this->matchSection($line)) !== null) {
                if ($extends === null) {
                    throw new \Exception('Error in file ' . $this->file . ' in line ' . $lineNumber . ' - \'@section\' has no meaning if view extends nothing.');
                }
                if ($sectionOpen !== null) {
                    throw new \Exception('Parse error in file ' . $this->file . ' in line ' . $lineNumber . ' - A \'@section\' is already open (no \'@endsection\' found).');
                }

                $sectionOpen = $sectionMatched;
                $sections[$sectionOpen] = '';

                continue;
            }

            if ($this->matchEndSection($line)) {
                if ($sectionOpen === null) {
                    throw new \Exception('Parse error in file ' . $this->file . ' in line ' . $lineNumber . ' - Cannot end section until no \'@section\' is open.');
                }

                $sectionOpen = null;
            }

            if ($this->matchExtra($line)) {
                if ($extraOpen) {
                    throw new \Exception('Parse error in file ' . $this->file . ' in line ' . $lineNumber . ' - An \'@extra\' is already open (no \'@endextra\' found).');
                }

                $extraOpen = true;

                continue;
            }

            if ($this->matchEndExtra($line)) {
                if (!$extraOpen) {
                    throw new \Exception('Parse error in file ' . $this->file . ' in line ' . $lineNumber . ' - Cannot end extra until no \'@extra\' is open.');
                }

                $extraOpen = false;
            }

            if ($sectionOpen !== null) {
                $sections[$sectionOpen] .= $line;
            }

            if ($extraOpen) {
                $offset = $extends === null ? 0 : 1;
                $extra[$offset] .= $line;
            }
        }

        fclose($fileHandle);

        return new ParsedFragment($extends, $css, $js, $sections, $extra);
    }

    private function matchCss(string $line): ?string
    {
        if (preg_match('/^\s*@css\((.*)\)\s*$/', $line, $matches) === 1) {
            return $matches[1];
        }

        return null;
    }

    private function matchJs(string $line): ?string
    {
        if (preg_match('/^\s*@js\((.*)\)\s*$/', $line, $matches) === 1) {
            return $matches[1];
        }

        return null;
    }

    private function matchExtends(string $line): ?string
    {
        if (preg_match('/^\s*@extends\(([\w\/]+)\)\s*$/', $line, $matches) === 1) {
            return $matches[1];
        }

        return null;
    }

    private function matchSection(string $line): ?string
    {
        if (preg_match('/^\s*@section\((\w+)\)\s*$/', $line, $matches) === 1) {
            return $matches[1];
        }

        return null;
    }

    private function matchEndSection(string $line): bool
    {
        return preg_match('/^\s*@endsection(?:\(\))?\s*$/', $line) === 1;
    }

    private function matchExtra(string $line): bool
    {
        return preg_match('/^\s*@extra(?:\(\))?\s*$/', $line) === 1;
    }

    private function matchEndExtra(string $line): bool
    {
        return preg_match('/^\s*@endextra(?:\(\))?\s*$/', $line) === 1;
    }
}