8 files changed, 723 insertions, 0 deletions
diff --git a/src/Credentials.php b/src/Credentials.php
new file mode 100644
index 0000000..bcc4a53
--- /dev/null
+++ b/src/Credentials.php
@@ -0,0 +1,16 @@
+<?php
+
+declare(strict_types=1);
+
+namespace TCB;
+
+final class Credentials
+{
+    public function __construct(
+        public readonly string $clientID,
+        public readonly string $clientSecret,
+        public readonly string $redirectURI,
+        public readonly string $state,
+    ) {
+    }
+}
diff --git a/src/HistoryStorage.php b/src/HistoryStorage.php
new file mode 100644
index 0000000..30d9ace
--- /dev/null
+++ b/src/HistoryStorage.php
@@ -0,0 +1,41 @@
+<?php
+
+declare(strict_types=1);
+
+namespace TCB;
+
+final class HistoryStorage
+{
+    public function __construct(
+        public array $playlists,
+        public array $history,
+        private readonly string $filename,
+    ) {}
+
+    static public function load(string $filename): self
+    {
+        $storage = is_readable($filename)
+            ? json_decode(file_get_contents($filename), true)
+            : [];
+
+        return new self(
+            playlists: $storage['playlists'] ?? [],
+            history: $storage['history'] ?? [],
+            filename: $filename,
+        );
+    }
+
+    public function save(): void
+    {
+        file_put_contents($this->filename, json_encode($this, JSON_PRETTY_PRINT));
+    }
+
+    public function saveSong(array $song): void
+    {
+        $this->history[$song['id']] = [
+            'timestamp' => time(),
+            'details' => $song,
+        ];
+        $this->save();
+    }
+}
diff --git a/src/HttpServer.php b/src/HttpServer.php
new file mode 100644
index 0000000..bdab9cc
--- /dev/null
+++ b/src/HttpServer.php
@@ -0,0 +1,246 @@
+<?php
+
+declare(strict_types=1);
+
+namespace TCB;
+
+use TCB\Request;
+use TCB\Response;
+use Throwable;
+
+final class HttpServer
+{
+    private array $handlers = [];
+    private bool $shouldClose = false;
+
+    public function __construct(
+        private readonly string $address,
+        private readonly int $port,
+        private readonly int $timeout,
+    ) {}
+
+    public function on(string $method, string $uri, callable $handler): void
+    {
+        $this->handlers[$uri][$method] = $handler;
+    }
+
+    public function get(string $uri, callable $handler): void
+    {
+        $this->on('GET', $uri, $handler);
+    }
+
+    public function post(string $uri, callable $handler): void
+    {
+        $this->on('POST', $uri, $handler);
+    }
+
+    /**
+     * Allows a route handler to trigger server shutdown after responding.
+     */
+    public function closeAfterResponse(): void
+    {
+        $this->shouldClose = true;
+    }
+
+    public function run(): void
+    {
+        $socket = stream_socket_server(
+            "tcp://$this->address:$this->port",
+            $errno,
+            $errstr,
+            STREAM_SERVER_BIND | STREAM_SERVER_LISTEN,
+        );
+
+        if ($socket === false) {
+            echo "errstr ($errno)\n";
+            exit(1);
+        }
+
+        while ($socket) {
+            $stream = stream_socket_accept($socket, $this->timeout);
+
+            if ($stream === false) {
+                continue;
+            }
+
+            $request = $this->processRequest($stream);
+
+            if (!$request) {
+                fclose($stream);
+                continue;
+            }
+
+            $response = $this->processResponse($request);
+
+            fwrite($stream, (string) $response);
+            fclose($stream);
+
+            // Shutdown if requested by handler.
+            if ($this->shouldClose) {
+                break;
+            }
+        }
+
+        fclose($socket);
+    }
+
+    /**
+     * @param resource $stream
+     */
+    private function processRequest($stream): ?Request
+    {
+        $lines = [];
+
+        while ($line = fgets($stream)) {
+            $line = rtrim($line, "\r\n");
+            if ($line !== '') {
+                $lines[] = $line;
+                continue;
+            }
+
+            break;
+        }
+
+        if (empty($lines)) {
+            return null;
+        }
+
+        // Process start line.
+        [$method, $uri, $httpVersion] = array_pad(
+            explode(' ', array_shift($lines)),
+            3,
+            '',
+        );
+
+        // Process uri.
+        $uri = explode('?', $uri, 2);
+        $path = $this->normalisePath(urldecode($uri[0]));
+        $params = [];
+        parse_str($uri[1] ?? '', $params);
+
+        // Process headers.
+        $headers = array_reduce($lines, function (array $carry, string $line): array {
+            $parts = explode(':', $line, 2);
+            $header = strtolower(trim($parts[0]));
+            $carry[$header] = trim($parts[1] ?? '');
+
+            return $carry;
+        }, []);
+
+        // Process the body.
+        $body = '';
+        $contentLength = (int) ($headers['content-length'] ?? 0);
+
+        if ($contentLength > 0) {
+            $remaining = $contentLength;
+
+            do {
+                $buffer = fread($stream, $remaining);
+
+                if ($buffer === false || $buffer === '') {
+                    break;
+                }
+
+                $body .= $buffer;
+                $bytesRead = strlen($body);
+                $remaining = $contentLength - $bytesRead;
+            } while ($bytesRead < $contentLength);
+        }
+
+        return new Request(
+            method: $method,
+            path: $path,
+            httpVersion: $httpVersion,
+            headers: $headers,
+            params: $params,
+            body: $body,
+        );
+    }
+
+    private function processResponse(Request $request): Response
+    {
+        try {
+            $pathHandlers = $this->handlers[$request->path] ?? null;
+
+            if ($pathHandlers !== null) {
+                $handler = $pathHandlers[$request->method] ?? null;
+
+                if ($handler === null) {
+                    $allowedMethods = implode(', ', array_keys($pathHandlers));
+
+                    return new Response(
+                        statusCode: 405,
+                        contentType: 'text/plain',
+                        body: '405 Method Not Allowed',
+                        headers: [
+                            'Allow' => $allowedMethods,
+                        ],
+                    );
+                }
+
+                return $handler($request, $this);
+            }
+
+            // Path not found in handlers -> Fall back to static files or 404.
+            $path = ltrim($request->path, '/');
+            if (is_file($path)) {
+                $statusCode = 200;
+                $contentType = $this->mimeType($path);
+                $body = file_get_contents($path);
+            } else {
+                $statusCode = 404;
+                $contentType = 'text/plain';
+                $body = "Could not locate [$path]";
+            }
+        } catch (Throwable $exception) {
+            $statusCode = 500;
+            $contentType = 'text/plain';
+            $body = $exception->getMessage();
+        }
+
+        return new Response(
+            statusCode: $statusCode,
+            contentType: $contentType,
+            body: $body,
+        );
+    }
+
+    private function normalisePath(string $path): string
+    {
+        $path = "/$path";
+
+        $parts = explode('/', $path);
+
+        $normalised = [];
+
+        foreach ($parts as $part) {
+            switch ($part) {
+                case '':
+                case '.':
+                    break;
+                case '..':
+                    array_pop($normalised);
+                    break;
+                default:
+                    $normalised[] = $part;
+                    break;
+            }
+        }
+
+        return '/' . implode('/', $normalised);
+    }
+
+    private function mimeType(string $path): string
+    {
+        return match (pathinfo($path, PATHINFO_EXTENSION)) {
+            'html' => 'text/html',
+            'jpeg' => 'image/jpeg',
+            'png' => 'image/png',
+            'txt' => 'text/plain',
+            'css' => 'text/css',
+            'js' => 'text/javascript',
+            'json' => 'application/json',
+            default => 'application/octet-stream',
+        };
+    }
+}
diff --git a/src/Request.php b/src/Request.php
new file mode 100644
index 0000000..9b4bd5d
--- /dev/null
+++ b/src/Request.php
@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types=1);
+
+namespace TCB;
+
+final class Request
+{
+    public function __construct(
+        public readonly string $method,
+        public readonly string $path,
+        public readonly string $httpVersion,
+        public readonly array $headers,
+        public readonly array $params,
+        public readonly string $body,
+    ) {}
+}
diff --git a/src/Response.php b/src/Response.php
new file mode 100644
index 0000000..d3c4f69
--- /dev/null
+++ b/src/Response.php
@@ -0,0 +1,50 @@
+<?php
+
+declare(strict_types=1);
+
+namespace TCB;
+
+final class Response
+{
+    /**
+     * @param array<string, string> $headers Key-value pairs of additional HTTP headers
+     */
+    public function __construct(
+        public readonly int $statusCode,
+        public readonly string $contentType,
+        public readonly string $body,
+        public readonly array $headers = [],
+    ) {}
+
+    public function __toString(): string
+    {
+        $reason = match ($this->statusCode) {
+            200 => 'OK',
+            400 => 'Bad Request',
+            401 => 'Unauthorized',
+            403 => 'Forbidden',
+            404 => 'Not Found',
+            405 => 'Method Not Allowed',
+            500 => 'Internal Server Error',
+            default => '',
+        };
+
+        $statusLine = trim("HTTP/1.1 {$this->statusCode} {$reason}");
+        $contentLength = strlen($this->body);
+
+        // Build base headers.
+        $formattedHeaders = [
+            $statusLine,
+            "Content-Type: $this->contentType",
+            "Content-Length: $contentLength",
+            "Connection: close",
+        ];
+
+        // Format and append custom headers.
+        foreach ($this->headers as $name => $value) {
+            $formattedHeaders[] = "$name: $value";
+        }
+
+        return implode("\r\n", $formattedHeaders) . "\r\n\r\n" . $this->body;
+    }
+}
diff --git a/src/SpotifyApiClient.php b/src/SpotifyApiClient.php
new file mode 100644
index 0000000..a78f05b
--- /dev/null
+++ b/src/SpotifyApiClient.php
@@ -0,0 +1,140 @@
+<?php
+
+declare(strict_types=1);
+
+namespace TCB;
+
+use TCB\TokenManager;
+use TCB\HistoryStorage;
+
+final class SpotifyApiClient
+{
+    public function __construct(
+        private readonly TokenManager $tokenManager,
+        private readonly HistoryStorage $historyStorage,
+    ) {}
+
+    public function pickRandomSongFromPlaylist(string $playlistName): array
+    {
+        echo "Picking a random song from the playlist $playlistName.\n";
+
+        if (
+            !array_key_exists($playlistName, $this->historyStorage->playlists)
+            || $this->historyStorage->playlists[$playlistName] === ''
+        ) {
+            $this->getPlaylistID($playlistName);
+        }
+
+        $items = $this->getPlaylistItems($this->historyStorage->playlists[$playlistName]);
+
+        if (!count($items)) {
+            echo "Playlist appears empty.\n";
+            exit(1);
+        }
+
+        $items = array_values(array_filter($items, function (array $item): bool {
+            return !array_key_exists($item['id'], $this->historyStorage->history);
+        }));
+
+        if (!count($items)) {
+            echo "No songs left to pick.\n";
+            exit(1);
+        }
+
+        $key = array_rand($items);
+
+        $song = $items[$key];
+
+        $this->historyStorage->saveSong($song);
+
+        return $song;
+    }
+
+    private function getPlaylistID(string $playlistName): void
+    {
+        echo "Looking up the Spotify playlist ID.\n";
+
+        $url = 'https://api.spotify.com/v1/me/playlists?limit=50';
+
+        $ch = curl_init();
+
+        while ($url !== null) {
+            curl_setopt_array($ch, [
+                CURLOPT_URL => $url,
+                CURLOPT_HTTPGET => true,
+                CURLOPT_HTTPHEADER => [
+                    "Authorization: Bearer {$this->tokenManager->getAccessToken()}",
+                ],
+                CURLOPT_RETURNTRANSFER => true,
+            ]);
+
+            $response = curl_exec($ch);
+            $statusCode = curl_getinfo($ch, CURLINFO_RESPONSE_CODE);
+
+            if ($statusCode !== 200) {
+                echo "Non-200 response from Spotify: $statusCode $response\n";
+                exit(1);
+            }
+
+            $data = json_decode($response, true) ?? [];
+
+            foreach ($data['items'] ?? [] as $item) {
+                if ($item['name'] === $playlistName) {
+                    $this->historyStorage->playlists[$playlistName] = $item['id'];
+                    $this->historyStorage->save();
+
+                    return;
+                }
+            }
+
+            $url = $data['next'] ?? null;
+        }
+
+        echo "Unable to find a playlist named $playlistName.\n";
+        exit(1);
+    }
+
+    private function getPlaylistItems(string $playlistID): array
+    {
+        $items = [];
+
+        $query = http_build_query([
+            'fields' => 'next,items(item(id,name,artists(name)))',
+        ]);
+
+        $url = "https://api.spotify.com/v1/playlists/$playlistID/items?limit=50&$query";
+
+        $ch = curl_init();
+
+        while ($url !== null) {
+            curl_setopt_array($ch, [
+                CURLOPT_URL => $url,
+                CURLOPT_HTTPGET => true,
+                CURLOPT_HTTPHEADER => [
+                    "Authorization: Bearer {$this->tokenManager->getAccessToken()}",
+                ],
+                CURLOPT_RETURNTRANSFER => true,
+            ]);
+
+            $response = curl_exec($ch);
+            $statusCode = curl_getinfo($ch, CURLINFO_RESPONSE_CODE);
+
+            if ($statusCode !== 200) {
+                echo "Non-200 response from Spotify: $statusCode $response\n";
+                exit(1);
+            }
+
+            $data = json_decode($response, true) ?? [];
+
+            foreach ($data['items'] ?? [] as $item) {
+                if (isset($item['item'])) {
+                    $items[] = $item['item'];
+                }
+            }
+
+            $url = $data['next'] ?? null;
+        }
+
+        return $items;
+    }
+}
diff --git a/src/TokenManager.php b/src/TokenManager.php
new file mode 100644
index 0000000..96b3969
--- /dev/null
+++ b/src/TokenManager.php
@@ -0,0 +1,179 @@
+<?php
+
+declare(strict_types=1);
+
+namespace TCB;
+
+use TCB\Credentials;
+use TCB\HttpServer;
+use TCB\Request;
+use TCB\Response;
+use TCB\TokenStorage;
+
+final class TokenManager
+{
+    private string $authorisationCode;
+
+    public function __construct(
+        private readonly Credentials $credentials,
+        private readonly HttpServer $httpServer,
+        private readonly TokenStorage $storage,
+    ) {}
+
+    public function getAccessToken(): string
+    {
+        if ($this->storage->accessToken === '' || $this->storage->refreshToken === '') {
+            $this->authorise();
+            $this->requestAccessToken();
+        }
+
+        if ($this->storage->expiresOn < time()) {
+            $this->refreshAccessToken();
+        }
+
+        return $this->storage->accessToken;
+    }
+
+    private function authorise(): void
+    {
+        $this->authorisationCode = '';
+
+        $this->httpServer->get(
+            '/callback',
+            function (Request $request, HttpServer $server): Response {
+                $server->closeAfterResponse();
+
+                if (
+                    !array_key_exists('state', $request->params)
+                    || $request->params['state'] !== $this->credentials->state
+                ) {
+                    $body = 'State mismatch.';
+                } elseif (array_key_exists('error', $request->params)) {
+                    $body = "Error from Spotify: {$request->params['error']}";
+                } elseif (!array_key_exists('code', $request->params)) {
+                    $body = "Missing authorisation code from Spotify.";
+                } else {
+                    $this->authorisationCode = $request->params['code'];
+                    $body = 'Authorisation code received from Spotify. You can close this page and go back to the terminal.';
+                }
+
+                return new Response(
+                    statusCode: 200,
+                    contentType: 'text/plain; charset=UTF-8',
+                    body: htmlspecialchars($body, ENT_QUOTES),
+                );
+            },
+        );
+
+        $query = http_build_query([
+            'response_type' => 'code',
+            'client_id' => $this->credentials->clientID,
+            'redirect_uri' => $this->credentials->redirectURI,
+            'state' => $this->credentials->state,
+            'scope' => 'playlist-read-private',
+            'show_dialog' => false,
+        ]);
+
+        echo "Visit the below URL in your browser to authorise access to Spotify.\n";
+        echo "https://accounts.spotify.com/authorize?$query\n";
+        echo "Waiting for authorisation from Spotify...\n";
+
+        $this->httpServer->run();
+
+        if ($this->authorisationCode === '') {
+            echo "Failed to get authorisation code from Spotify.\n";
+            exit(1);
+        }
+    }
+
+    private function requestAccessToken(): void
+    {
+        echo "Requesting an access token from Spotify.\n";
+
+        $ch = curl_init();
+
+        curl_setopt_array($ch, [
+            CURLOPT_URL => 'https://accounts.spotify.com/api/token',
+            CURLOPT_POST => true,
+            CURLOPT_HTTPHEADER => [
+                'Authorization: Basic ' . base64_encode($this->credentials->clientID . ':' . $this->credentials->clientSecret),
+                'Content-Type: application/x-www-form-urlencoded',
+            ],
+            CURLOPT_POSTFIELDS => http_build_query([
+                'grant_type'  => 'authorization_code',
+                'code' => $this->authorisationCode,
+                'redirect_uri' => $this->credentials->redirectURI,
+            ]),
+            CURLOPT_RETURNTRANSFER => true,
+        ]);
+
+        $response = curl_exec($ch);
+        $statusCode = curl_getinfo($ch, CURLINFO_RESPONSE_CODE);
+
+        if ($statusCode !== 200) {
+            echo "Non 200 response from Spotify: $statusCode $response\n";
+            exit(1);
+        }
+
+        $data = json_decode($response, true) ?? [];
+
+        $accessToken = $data['access_token'] ?? '';
+        $refreshToken = $data['refresh_token'] ?? '';
+        $expiresIn = $data['expires_in'] ?? 0;
+
+        if ($accessToken === '' || $refreshToken === '') {
+            echo "Failed to get access token from Spotify.\n";
+            exit(1);
+        }
+
+        $this->storage->accessToken = $accessToken;
+        $this->storage->refreshToken = $refreshToken;
+        $this->storage->expiresOn = time() + $expiresIn;
+        $this->storage->save();
+    }
+
+    private function refreshAccessToken(): void
+    {
+        echo "Refreshing the Spotify access token.\n";
+
+        $ch = curl_init();
+
+        curl_setopt_array($ch, [
+            CURLOPT_URL => 'https://accounts.spotify.com/api/token',
+            CURLOPT_POST => true,
+            CURLOPT_HTTPHEADER => [
+                'Authorization: Basic ' . base64_encode($this->credentials->clientID . ':' . $this->credentials->clientSecret),
+                'Content-Type: application/x-www-form-urlencoded',
+            ],
+            CURLOPT_POSTFIELDS => http_build_query([
+                'grant_type'  => 'refresh_token',
+                'refresh_token' => $this->storage->refreshToken,
+            ]),
+            CURLOPT_RETURNTRANSFER => true,
+        ]);
+
+        $response = curl_exec($ch);
+        $statusCode = curl_getinfo($ch, CURLINFO_RESPONSE_CODE);
+
+        if ($statusCode !== 200) {
+            echo "Non 200 response from Spotify: $statusCode $response\n";
+            exit(1);
+        }
+
+        $data = json_decode($response, true) ?? [];
+
+        $accessToken = $data['access_token'] ?? '';
+        $refreshToken = $data['refresh_token'] ?? $this->storage->refreshToken;
+        $expiresIn = $data['expires_in'] ?? 0;
+
+        if ($accessToken === '' || $refreshToken === '') {
+            echo "Failed to refresh the Spotify access token.\n";
+            exit(1);
+        }
+
+        $this->storage->accessToken = $accessToken;
+        $this->storage->refreshToken = $refreshToken;
+        $this->storage->expiresOn = time() + $expiresIn;
+        $this->storage->save();
+    }
+}
diff --git a/src/TokenStorage.php b/src/TokenStorage.php
new file mode 100644
index 0000000..d7b8db8
--- /dev/null
+++ b/src/TokenStorage.php
@@ -0,0 +1,34 @@
+<?php
+
+declare(strict_types=1);
+
+namespace TCB;
+
+final class TokenStorage
+{
+    public function __construct(
+        public string $accessToken,
+        public string $refreshToken,
+        public int $expiresOn,
+        private readonly string $filename,
+    ) {}
+
+    static public function load(string $filename): self
+    {
+        $storage = is_readable($filename)
+            ? json_decode(file_get_contents($filename), true)
+            : [];
+
+        return new self(
+            accessToken: $storage['accessToken'] ?? '',
+            refreshToken: $storage['refreshToken'] ?? '',
+            expiresOn: $storage['expiresOn'] ?? 0,
+            filename: $filename,
+        );
+    }
+
+    public function save(): void
+    {
+        file_put_contents($this->filename, json_encode($this, JSON_PRETTY_PRINT));
+    }
+}