//! Multi-backend encryption example.
//!
//! Demonstrates how to switch between different encryption backends
//! using the same unified API.
//!
//! # Key Point
//!
//! The same code path works with Age, SOPS, AWS KMS, GCP KMS, Azure KMS,
//! SecretumVault. Just change the backend specification - no code changes
//! needed!
//!
//! # Usage
//!
//! ```bash
//! # Test with Age backend
//! age-keygen -o ~/.age/key.txt
//! cargo run --example multi_backend --features age
//!
//! # Test with SOPS backend (requires .sops.yaml)
//! cargo run --example multi_backend --features sops
//!
//! # Test with both (shows feature-gating)
//! cargo run --example multi_backend --features age,sops
//! ```

use encrypt::{decrypt, encrypt, is_available, BackendSpec};

fn main() -> Result<(), Box<dyn std::error::Error>> {
    println!("=== Multi-Backend Encryption Example ===\n");

    let secret = "my-application-secret";

    // Define specs for different backends
    let backends = vec![
        ("Age (local)", BackendSpec::age_default()),
        ("SOPS (AWS KMS)", BackendSpec::sops()),
        (
            "SecretumVault (PQC)",
            BackendSpec::secretumvault("https://vault.internal:8200", "hvs.token", "app-key"),
        ),
        (
            "AWS KMS",
            BackendSpec::aws_kms("us-east-1", "arn:aws:kms:us-east-1:123456789:key/12345678"),
        ),
    ];

    println!("Testing encryption with available backends:\n");

    let mut success_count = 0;
    let mut skipped_count = 0;

    for (name, spec) in backends {
        print!("{:<30} ", format!("{}...", name));

        // Check if backend feature is enabled
        if !is_available(&spec) {
            println!("SKIPPED (feature not enabled)");
            skipped_count += 1;
            continue;
        }

        // Try encryption with this backend
        match encrypt(secret, &spec) {
            Ok(ciphertext) => {
                // Try decryption
                match decrypt(&ciphertext, &spec) {
                    Ok(plaintext) => {
                        if plaintext == secret {
                            println!("✓ SUCCESS");
                            success_count += 1;
                        } else {
                            println!("✗ FAILED (roundtrip mismatch)");
                        }
                    }
                    Err(e) => {
                        println!("✗ FAILED (decrypt: {})", e);
                    }
                }
            }
            Err(e) => {
                println!("✗ FAILED (encrypt: {})", e);
            }
        }
    }

    println!("\n=== Results ===");
    println!("Successful: {}", success_count);
    println!("Skipped (feature not enabled): {}", skipped_count);

    // Show how to handle backend fallback
    println!("\n=== Backend Fallback Pattern ===\n");
    println!("Common pattern: Try production backend, fall back to local\n");

    // Try SecretumVault (production)
    let secretumvault_spec =
        BackendSpec::secretumvault("https://vault.prod:8200", "token", "app-key");

    if is_available(&secretumvault_spec) {
        println!("Using SecretumVault (production, post-quantum ready)");
        match encrypt(secret, &secretumvault_spec) {
            Ok(_) => println!("✓ Encrypted with SecretumVault"),
            Err(_) => println!("! SecretumVault unavailable, trying fallback..."),
        }
    } else {
        // Fallback to Age
        let age_spec = BackendSpec::age_default();
        if is_available(&age_spec) {
            println!("SecretumVault not available");
            println!("Falling back to Age (local, X25519)");
            match encrypt(secret, &age_spec) {
                Ok(_) => println!("✓ Encrypted with Age"),
                Err(e) => println!("✗ Age also failed: {}", e),
            }
        }
    }

    // Show available backends
    println!("\n=== Configuration Examples ===\n");

    println!("Age (local X25519):");
    println!("  BackendSpec::age_default()");
    println!("  BackendSpec::age(\"/custom/path.txt\")\n");

    println!("SOPS (multi-KMS via .sops.yaml):");
    println!("  BackendSpec::sops()\n");

    println!("SecretumVault (post-quantum ready):");
    println!("  BackendSpec::secretumvault(\"https://vault:8200\", \"token\", \"key\")\n");

    println!("AWS KMS:");
    println!("  BackendSpec::aws_kms(\"us-east-1\", \"arn:aws:kms:...:key/...\")\n");

    println!("GCP KMS:");
    println!("  BackendSpec::gcp_kms(\"project\", \"global\", \"key\", \"global\")\n");

    println!("Azure KMS:");
    println!("  BackendSpec::azure_kms(\"vault-name\", \"tenant-id\")\n");

    println!("Key Architecture Benefits:");
    println!("  ✓ Same API for all backends");
    println!("  ✓ Feature-gated compilation");
    println!("  ✓ Easy to switch backends");
    println!("  ✓ Fallback support");
    println!("  ✓ No backend-specific code in application");

    Ok(())
}