use std::collections::{HashMap, HashSet};
use std::path::Path;

use anyhow::{bail, Context, Result};
use zeroize::Zeroizing;

use crate::crypto::{decrypt_chunk, FORMAT_VERSION_V1, FORMAT_VERSION_V2};
use crate::storage::Database;

/// Bericht über das Ergebnis einer Container-Integritätsprüfung.
#[derive(Debug, Clone)]
pub struct VerificationReport {
    pub container_path: String,
    pub format_version: u32,
    pub sqlite_ok: bool,
    pub sqlite_errors: Vec<String>,
    pub header_ok: bool,
    pub header_error: Option<String>,
    pub total_nodes: usize,
    pub total_dirs: usize,
    pub total_files: usize,
    pub total_chunks: usize,
    pub total_bytes_decrypted: u64,
    pub corrupted_chunks: usize,
    pub orphan_nodes: usize,
    pub errors: Vec<String>,
}

impl VerificationReport {
    pub fn is_healthy(&self) -> bool {
        self.sqlite_ok
            && self.header_ok
            && self.corrupted_chunks == 0
            && self.orphan_nodes == 0
            && self.errors.is_empty()
    }
}

/// Führt eine detaillierte Integritäts- und Bitrot-Prüfung auf einem Sanctum-Container durch.
pub fn verify_container(
    container_path: &Path,
    dek: Option<&Zeroizing<[u8; 32]>>,
    full_chunks: bool,
) -> Result<VerificationReport> {
    if !container_path.exists() {
        bail!("Containerdatei '{}' existiert nicht.", container_path.display());
    }

    let db = Database::open(container_path)
        .context("Konnte Container-Datenbank nicht öffnen")?;

    let mut report = VerificationReport {
        container_path: container_path.display().to_string(),
        format_version: 0,
        sqlite_ok: true,
        sqlite_errors: Vec::new(),
        header_ok: true,
        header_error: None,
        total_nodes: 0,
        total_dirs: 0,
        total_files: 0,
        total_chunks: 0,
        total_bytes_decrypted: 0,
        corrupted_chunks: 0,
        orphan_nodes: 0,
        errors: Vec::new(),
    };

    // 1. SQLite B-Tree & Foreign Key Prüfung
    let sqlite_issues = db.run_sqlite_integrity_check()
        .context("Fehler bei der Ausführung des SQLite integrity_check")?;
    if !sqlite_issues.is_empty() {
        report.sqlite_ok = false;
        report.sqlite_errors = sqlite_issues;
    }

    // 2. Header & Magic Bytes Prüfung
    let meta = match db.read_meta() {
        Ok(m) => {
            report.format_version = m.version;
            if m.version != FORMAT_VERSION_V1 && m.version != FORMAT_VERSION_V2 {
                report.header_ok = false;
                report.header_error = Some(format!("Unbekannte Formatversion: {}", m.version));
            }
            if m.kdf_salt.len() != 16 {
                report.header_ok = false;
                report.header_error = Some("Ungültige KDF-Salt-Länge".to_string());
            }
            Some(m)
        }
        Err(e) => {
            report.header_ok = false;
            report.header_error = Some(format!("{e}"));
            None
        }
    };

    // 3. Node-Hierarchie & Strukturprüfung
    let (dirs, files, chunks_count) = db.count_nodes_and_chunks()
        .context("Fehler beim Zählen der Knoten und Chunks")?;
    report.total_dirs = dirs;
    report.total_files = files;
    report.total_chunks = chunks_count;

    let all_nodes = db.list_all_nodes().context("Fehler beim Laden der Knotenliste")?;
    report.total_nodes = all_nodes.len();

    let mut node_map = HashMap::new();
    for node in &all_nodes {
        node_map.insert(node.id, node.clone());
    }

    // Root-Knoten prüfen (id = 1 und optional id = 2 für Hidden Vault)
    match node_map.get(&1) {
        Some(root) => {
            if !root.is_dir {
                report.errors.push("Root-Knoten (id=1) ist nicht als Verzeichnis markiert!".to_string());
            }
            if root.parent_id.is_some() {
                report.errors.push("Root-Knoten (id=1) darf keinen Parent haben!".to_string());
            }
        }
        None => {
            report.errors.push("Root-Knoten (id=1) fehlt in der nodes-Tabelle!".to_string());
        }
    }

    if let Some(root2) = node_map.get(&2) {
        if !root2.is_dir {
            report.errors.push("Root-Knoten (id=2) ist nicht als Verzeichnis markiert!".to_string());
        }
        if root2.parent_id.is_some() {
            report.errors.push("Root-Knoten (id=2) darf keinen Parent haben!".to_string());
        }
    }

    // Alle anderen Knoten prüfen: Existenz des Parents, keine Zyklen
    for node in &all_nodes {
        if node.id == 1 || node.id == 2 {
            continue;
        }

        match node.parent_id {
            Some(pid) => match node_map.get(&pid) {
                Some(parent) => {
                    if !parent.is_dir {
                        report.errors.push(format!(
                            "Knoten '{}' (id={}) hat einen Parent (id={}), der kein Verzeichnis ist!",
                            node.name, node.id, pid
                        ));
                    }
                }
                None => {
                    report.orphan_nodes += 1;
                    report.errors.push(format!(
                        "Verwaister Knoten: '{}' (id={}) verweist auf nicht-existenten Parent id={}",
                        node.name, node.id, pid
                    ));
                }
            },
            None => {
                report.orphan_nodes += 1;
                report.errors.push(format!(
                    "Verwaister Knoten ohne Parent: '{}' (id={})",
                    node.name, node.id
                ));
            }
        }

        // Zyklenprüfung
        let mut visited = HashSet::new();
        visited.insert(node.id);
        let mut curr_parent = node.parent_id;
        while let Some(pid) = curr_parent {
            if !visited.insert(pid) {
                report.errors.push(format!(
                    "Zyklische Verzeichnisreferenz bei Knoten '{}' (id={}) entdeckt!",
                    node.name, node.id
                ));
                break;
            }
            curr_parent = node_map.get(&pid).and_then(|n| n.parent_id);
        }
    }

    // Ermittle die Abstammung aller Knoten zu Root 1 (Vault 0) bzw. Root 2 (Vault 1)
    let mut vault0_nodes = HashSet::new();
    let mut vault1_nodes = HashSet::new();
    vault0_nodes.insert(1i64);
    if node_map.contains_key(&2) {
        vault1_nodes.insert(2i64);
    }

    let mut changed = true;
    while changed {
        changed = false;
        for node in &all_nodes {
            if let Some(pid) = node.parent_id {
                if vault0_nodes.contains(&pid) && !vault0_nodes.contains(&node.id) {
                    vault0_nodes.insert(node.id);
                    changed = true;
                } else if vault1_nodes.contains(&pid) && !vault1_nodes.contains(&node.id) {
                    vault1_nodes.insert(node.id);
                    changed = true;
                }
            }
        }
    }

    // Falls ein DEK übergeben wurde: Bestimme, zu welchem Vault er gehört
    let active_vault_nodes = if let Some(active_dek) = dek {
        let is_vault1 = {
            let mut found_v1 = false;
            for node in &all_nodes {
                if node.parent_id == Some(2) {
                    if crate::crypto::decrypt_node_name(active_dek, 2, &node.name).is_some() {
                        found_v1 = true;
                        break;
                    }
                }
            }
            found_v1
        };

        if is_vault1 {
            Some(&vault1_nodes)
        } else {
            Some(&vault0_nodes)
        }
    } else {
        None
    };

    // 4. Kryptografische Chunk- & AEAD-Authentifizierungsprüfung
    let chunk_headers = db.list_all_chunk_headers()
        .context("Fehler beim Abrufen der Chunk-Liste")?;

    let format_version = meta.as_ref().map(|m| m.version).unwrap_or(FORMAT_VERSION_V2);

    for (node_id, chunk_index) in chunk_headers {
        if !node_map.contains_key(&node_id) {
            report.errors.push(format!(
                "Verwaister Daten-Chunk: Node #{node_id} Chunk #{chunk_index} gehört zu keinem bekannten Inode!"
            ));
        }

        if let (Some(active_dek), Some(target_nodes)) = (dek, active_vault_nodes) {
            // Nur Chunks verifizieren, die zum verifizierten Tresor gehören (kein Falschalarm für Hidden Vault)
            if target_nodes.contains(&node_id) && full_chunks {
                match db.read_chunk(node_id, chunk_index) {
                    Ok(Some(record)) => {
                        match decrypt_chunk(
                            active_dek,
                            node_id,
                            chunk_index,
                            &record.ciphertext,
                            &record.nonce,
                            &record.tag,
                            format_version,
                        ) {
                            Ok(plaintext) => {
                                report.total_bytes_decrypted += plaintext.len() as u64;
                            }
                            Err(e) => {
                                report.corrupted_chunks += 1;
                                report.errors.push(format!(
                                    "AEAD/Integritätsfehler bei Node #{node_id} Chunk #{chunk_index}: {e}"
                                ));
                            }
                        }
                    }
                    Ok(None) => {
                        report.errors.push(format!(
                            "Chunk #{chunk_index} für Node #{node_id} in Index gefunden, aber Daten nicht lesbar!"
                        ));
                    }
                    Err(e) => {
                        report.corrupted_chunks += 1;
                        report.errors.push(format!(
                            "DB-Lesefehler bei Node #{node_id} Chunk #{chunk_index}: {e}"
                        ));
                    }
                }
            }
        }
    }

    Ok(report)
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::crypto::{
        derive_kek, encrypt_chunk, generate_dek, generate_salt, wrap_dek, KdfParams, FORMAT_VERSION,
    };
    use std::fs;
    use std::path::PathBuf;

    #[test]
    fn test_verify_healthy_container() {
        let temp_dir = std::env::temp_dir();
        let container_path: PathBuf =
            temp_dir.join(format!("test_verify_ok_{}.sanctum", std::process::id()));

        if container_path.exists() {
            let _ = fs::remove_file(&container_path);
        }

        let password = "HealthyTestPassword123!";
        let salt = generate_salt();
        let kdf_params = KdfParams {
            memory_cost: 1024,
            time_cost: 1,
            parallelism: 1,
        };
        let kek = derive_kek(password, &salt, &kdf_params).unwrap();
        let dek = generate_dek();
        let (wrapped_dek, nonce, tag) = wrap_dek(&kek, &dek).unwrap();

        let db = Database::open(&container_path).unwrap();
        db.init_schema(&salt, &kdf_params, &wrapped_dek, &nonce, &tag).unwrap();

        // Verzeichnis & Datei anlegen
        let folder = db.create_node(1, "photos", true).unwrap();
        let file = db.create_node(folder.id, "img.jpg", false).unwrap();

        // 2 Chunks schreiben
        let chunk0_data = b"Sample JPEG data header and pixels";
        let (ct0, n0, t0) = encrypt_chunk(&dek, file.id, 0, chunk0_data, FORMAT_VERSION).unwrap();
        db.write_chunk(file.id, 0, &n0, &t0, &ct0).unwrap();

        let chunk1_data = b"Additional payload data bytes";
        let (ct1, n1, t1) = encrypt_chunk(&dek, file.id, 1, chunk1_data, FORMAT_VERSION).unwrap();
        db.write_chunk(file.id, 1, &n1, &t1, &ct1).unwrap();

        db.update_node_size_and_time(file.id, (chunk0_data.len() + chunk1_data.len()) as u64, 1000).unwrap();
        db.checkpoint().unwrap();

        // Verifizieren
        let report = verify_container(&container_path, Some(&dek), true).expect("Verify container");
        assert!(report.is_healthy(), "Container must be healthy, report: {:?}", report);
        assert_eq!(report.total_files, 1);
        assert_eq!(report.total_dirs, 3); // Root 1 + Root 2 (Plausible Deniability) + photos
        assert_eq!(report.total_chunks, 2);
        assert_eq!(report.corrupted_chunks, 0);
        assert_eq!(report.orphan_nodes, 0);

        let _ = fs::remove_file(&container_path);
    }

    #[test]
    fn test_verify_detects_bitrot() {
        let temp_dir = std::env::temp_dir();
        let container_path: PathBuf =
            temp_dir.join(format!("test_verify_bitrot_{}.sanctum", std::process::id()));

        if container_path.exists() {
            let _ = fs::remove_file(&container_path);
        }

        let password = "BitrotTestPassword123!";
        let salt = generate_salt();
        let kdf_params = KdfParams {
            memory_cost: 1024,
            time_cost: 1,
            parallelism: 1,
        };
        let kek = derive_kek(password, &salt, &kdf_params).unwrap();
        let dek = generate_dek();
        let (wrapped_dek, nonce, tag) = wrap_dek(&kek, &dek).unwrap();

        let db = Database::open(&container_path).unwrap();
        db.init_schema(&salt, &kdf_params, &wrapped_dek, &nonce, &tag).unwrap();

        let file = db.create_node(1, "document.pdf", false).unwrap();
        let chunk_data = b"Vital documents that must not be corrupted";
        let (ct, n, t) = encrypt_chunk(&dek, file.id, 0, chunk_data, FORMAT_VERSION).unwrap();
        db.write_chunk(file.id, 0, &n, &t, &ct).unwrap();
        db.checkpoint().unwrap();
        drop(db);

        // Bitrot simulieren: Wir flippen 1 Byte im Ciphertext in SQLite direkt
        let conn = rusqlite::Connection::open(&container_path).unwrap();
        let mut corrupted_ct = ct.clone();
        corrupted_ct[4] ^= 0xFF; // Bit-Flip!
        conn.execute(
            "UPDATE chunks SET ciphertext = ?1 WHERE node_id = ?2 AND chunk_index = 0",
            rusqlite::params![corrupted_ct, file.id],
        ).unwrap();
        drop(conn);

        // Verifizieren: Muss Bitrot via AEAD Tag-Fehler sofort entlarven!
        let report = verify_container(&container_path, Some(&dek), true).expect("Verify container");
        assert!(!report.is_healthy(), "Container must report unhealthy due to bitrot");
        assert_eq!(report.corrupted_chunks, 1, "Must detect exactly 1 corrupted chunk");
        assert!(report.errors.iter().any(|e| e.contains("AEAD/Integritätsfehler")));

        let _ = fs::remove_file(&container_path);
    }
}