%%{init: {'theme': 'base', 'themeVariables': { 'primaryColor': '#fff', 'edgeLabelBackground':'#fff', 'tertiaryColor': '#f4f4f4', 'fontSize':'28px'}, 'flowchart': {'curve': 'basis', 'nodeSpacing': 20, 'rankSpacing': 50}} }%%

flowchart TD
    %% Global Styling
    classDef presentation stroke:#1565c0,stroke-width:5px,color:#0d47a1,rx:10,ry:10;
    classDef business stroke:#7b1fa2,stroke-width:5px,color:#4a148c,rx:10,ry:10;
    classDef data stroke:#2e7d32,stroke-width:5px,color:#1b5e20,rx:10,ry:10;
    classDef storage stroke:#e65100,stroke-width:5px,color:#bf360c,rx:5,ry:5;
    classDef external stroke:#c2185b,stroke-width:5px,color:#880e4f,rx:10,ry:10;

    %% Nodes (no subgraph boxes)
    A[**Streamlit Web Interface**]
    B[**User Authentication**]
    C[**Role-Based Navigation**]

    D[**User Management**]
    E[**Book Management**]
    F[**Borrowing System**]
    G[**Analytics Engine**]
    H[**Security Manager**]
    I[**PDF Library Manager**]

    J[**Database Manager**]
    K[**File Handler**]
    L[**Cache Manager**]

    M[(**SQLite Database**)]
    N[(**File System Storage**)]
    O[(**Session State**)]

    P[**Email Service**]
    Q[**Backup System**]
    R[**Export Services**]

    %% Connections (all solid and bold)
    A ==> B
    A ==> C
    
    B ==> H
    
    C ==> D
    C ==> E
    C ==> F
    C ==> G
    C ==> I

    D ==> J
    E ==> J
    F ==> J
    G ==> J
    H ==> J
    I ==> J
    I ==> K
    
    J ==> M
    J ==> O
    K ==> N
    
    G ==> P
    F ==> P
    J ==> Q
    G ==> R

    %% Assign Classes
    class A,B,C presentation
    class D,E,F,G,H,I business
    class J,K,L data
    class M,N,O storage
    class P,Q,R external