CourseHub: AJAX video course player (PHP + MySQL + Bootstrap + Plyr)

Scans nested course folders for mp4s, tracks per-user resume position
and per-folder progress. SPA frontend with hash routing over a JSON API;
range-request streaming via stream.php.

schema.sql

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+-- CourseHub schema (MySQL / MariaDB)
+CREATE DATABASE IF NOT EXISTS coursehub CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
+USE coursehub;
+
+CREATE TABLE IF NOT EXISTS users (
+    id            INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
+    username      VARCHAR(50)  NOT NULL UNIQUE,
+    password_hash VARCHAR(255) NOT NULL,
+    created_at    TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP
+) ENGINE=InnoDB;
+
+-- One row per directory found under VIDEOS_ROOT.
+-- `path` is the relative path from VIDEOS_ROOT, e.g. "Course 1/Intro".
+CREATE TABLE IF NOT EXISTS folders (
+    id         INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
+    parent_id  INT UNSIGNED NULL,
+    name       VARCHAR(255) NOT NULL,
+    path       VARCHAR(700) NOT NULL UNIQUE,
+    depth      INT UNSIGNED NOT NULL DEFAULT 0,
+    sort_order INT UNSIGNED NOT NULL DEFAULT 0,
+    is_missing TINYINT(1) NOT NULL DEFAULT 0,
+    created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    CONSTRAINT fk_folders_parent FOREIGN KEY (parent_id)
+        REFERENCES folders(id) ON DELETE CASCADE,
+    INDEX idx_folders_parent (parent_id)
+) ENGINE=InnoDB;
+
+CREATE TABLE IF NOT EXISTS videos (
+    id               INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
+    folder_id        INT UNSIGNED NOT NULL,
+    name             VARCHAR(255) NOT NULL,   -- display name, filename without .mp4
+    filename         VARCHAR(255) NOT NULL,
+    path             VARCHAR(700) NOT NULL UNIQUE,  -- relative path incl. filename
+    size_bytes       BIGINT UNSIGNED NOT NULL DEFAULT 0,
+    duration_seconds FLOAT NULL,              -- filled in by the player on first load
+    sort_order       INT UNSIGNED NOT NULL DEFAULT 0,
+    is_missing       TINYINT(1) NOT NULL DEFAULT 0,
+    created_at       TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    CONSTRAINT fk_videos_folder FOREIGN KEY (folder_id)
+        REFERENCES folders(id) ON DELETE CASCADE,
+    INDEX idx_videos_folder (folder_id)
+) ENGINE=InnoDB;
+
+-- Per-user playback state: resume position + completion flag.
+CREATE TABLE IF NOT EXISTS video_progress (
+    user_id          INT UNSIGNED NOT NULL,
+    video_id         INT UNSIGNED NOT NULL,
+    position_seconds FLOAT NOT NULL DEFAULT 0,
+    duration_seconds FLOAT NULL,
+    completed        TINYINT(1) NOT NULL DEFAULT 0,
+    updated_at       TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP
+        ON UPDATE CURRENT_TIMESTAMP,
+    PRIMARY KEY (user_id, video_id),
+    CONSTRAINT fk_vp_user  FOREIGN KEY (user_id)  REFERENCES users(id)  ON DELETE CASCADE,
+    CONSTRAINT fk_vp_video FOREIGN KEY (video_id) REFERENCES videos(id) ON DELETE CASCADE,
+    INDEX idx_vp_user_updated (user_id, updated_at)
+) ENGINE=InnoDB;