<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.

namespace aiprovider_openai;

use core_ai\ai_image;
use GuzzleHttp\Psr7\Request;
use GuzzleHttp\Psr7\Uri;
use Psr\Http\Message\RequestInterface;
use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\UriInterface;

/**
 * Class process image generation.
 *
 * @package    aiprovider_openai
 * @copyright  2024 Matt Porritt <matt.porritt@moodle.com>
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class process_generate_image extends abstract_processor {
    /** @var int The number of images to generate dall-e-3 only supports 1. */
    private int $numberimages = 1;

    #[\Override]
    protected function get_endpoint(): UriInterface {
        return new Uri(get_config('aiprovider_openai', 'action_generate_image_endpoint'));
    }

    #[\Override]
    protected function get_model(): string {
        return get_config('aiprovider_openai', 'action_generate_image_model');
    }

    #[\Override]
    protected function query_ai_api(): array {
        $response = parent::query_ai_api();

        // If the request was successful, save the image to a file.
        if ($response['success']) {
            $fileobj = $this->create_file_from_response(
                $this->action->get_configuration('userid'),
                $response
            );
            // Add the file to the response, so the calling placement can do whatever they want with it.
            $response['draftfile'] = $fileobj;
        }

        return $response;
    }

    /**
     * Convert the given aspect ratio to an image size compatible with the model's API.
     *
     * DALL-E 3: square=1024x1024, landscape=1792x1024, portrait=1024x1792.
     * GPT image models: square=1024x1024, landscape=1536x1024, portrait=1024x1536.
     *
     * @param string $ratio The aspect ratio of the image (square, landscape, portrait).
     * @return string The size string for the API request.
     */
    private function calculate_size(string $ratio): string {
        if (str_starts_with($this->get_model(), 'dall-e')) {
            if ($ratio === 'square') {
                $size = '1024x1024';
            } else if ($ratio === 'landscape') {
                $size = '1792x1024';
            } else if ($ratio === 'portrait') {
                $size = '1024x1792';
            } else {
                throw new \coding_exception('Invalid aspect ratio: ' . $ratio);
            }
        } else {
            if ($ratio === 'square') {
                $size = '1024x1024';
            } else if ($ratio === 'landscape') {
                $size = '1536x1024';
            } else if ($ratio === 'portrait') {
                $size = '1024x1536';
            } else {
                throw new \coding_exception('Invalid aspect ratio: ' . $ratio);
            }
        }
        return $size;
    }

    /**
     * Convert the given quality setting to the value expected by the model's API.
     *
     * DALL-E models accept the Moodle values directly (standard, hd).
     * GPT image models map them: standard -> medium, hd -> high.
     *
     * @param string $quality The quality setting (standard, hd).
     * @return string The quality value for the API request.
     */
    private function calculate_quality(string $quality): string {
        if (str_starts_with($this->get_model(), 'dall-e')) {
            return $quality;
        }
        if ($quality === 'standard') {
            return 'medium';
        } else if ($quality === 'hd') {
            return 'high';
        }
        throw new \coding_exception('Invalid quality: ' . $quality);
    }

    #[\Override]
    protected function create_request_object(string $userid): RequestInterface {
        $model = $this->get_model();
        $body = (object) [
            'prompt' => $this->action->get_configuration('prompttext'),
            'model' => $model,
            'n' => $this->numberimages,
            'quality' => $this->calculate_quality($this->action->get_configuration('quality')),
            'size' => $this->calculate_size($this->action->get_configuration('aspectratio')),
            'user' => $userid,
        ];

        // DALL-E models use response_format=b64_json and support style;
        // GPT image models use output_format instead and do not accept style.
        if (str_starts_with($model, 'dall-e')) {
            $body->response_format = 'b64_json';
            $body->style = $this->action->get_configuration('style');
        } else {
            $body->output_format = 'png';
        }

        return new Request(
            method: 'POST',
            uri: '',
            body: json_encode($body, JSON_UNESCAPED_SLASHES),
            headers: [
                'Content-Type' => 'application/json',
            ],
        );
    }

    #[\Override]
    protected function handle_api_success(ResponseInterface $response): array {
        $responsebody = $response->getBody();
        $bodyobj = json_decode($responsebody->getContents());

        return [
            'success' => true,
            'b64json' => $bodyobj->data[0]->b64_json,
            'output_format' => $bodyobj->output_format ?? 'png',
            'revisedprompt' => $bodyobj->data[0]->revised_prompt ?? '',
        ];
    }

    /**
     * Decode the base64-encoded image from the API response, add a watermark,
     * and store it as a draft file for the given user.
     *
     * Placements can't interact with the provider AI directly,
     * therefore we need to provide the image file in a format that can
     * be used by placements. So we use the file API.
     *
     * @param int $userid The user id.
     * @param array $response Response from the AI provider, containing 'b64json' and 'output_format'.
     * @return \stored_file The stored draft file.
     */
    private function create_file_from_response(int $userid, array $response): \stored_file {
        global $CFG;

        require_once("{$CFG->libdir}/filelib.php");

        // Decode the image and store in temp dir.
        $b64json = $response['b64json'];
        $imagebytes = base64_decode($b64json);
        $filename = substr(hash('sha512', $b64json), 0, 16) . '.' . $response['output_format'];
        $tempdst = make_request_directory() . DIRECTORY_SEPARATOR . $filename;
        file_put_contents($tempdst, $imagebytes);

        $image = new ai_image($tempdst);
        $image->add_watermark()->save();

        // We put the file in the user draft area initially.
        // Placements (on behalf of the user) can then move it to the correct location.
        $fileinfo = new \stdClass();
        $fileinfo->contextid = \context_user::instance($userid)->id;
        $fileinfo->filearea = 'draft';
        $fileinfo->component = 'user';
        $fileinfo->itemid = file_get_unused_draft_itemid();
        $fileinfo->filepath = '/';
        $fileinfo->filename = $filename;

        $fs = get_file_storage();
        return $fs->create_file_from_string($fileinfo, file_get_contents($tempdst));
    }
}