//! `migrate-nfc-filenames` — one-shot CLI to NFC-normalize
//! `storage.files.name` across an OxiCloud instance.
//!
//! Why: PostgreSQL compares bytes literally and the `UNIQUE`
//! index on `(folder_id, name, user_id) WHERE NOT is_trashed`
//! does not catch Unicode normalization differences. macOS APFS
//! stores filenames in NFD; browsers post NFC. A file uploaded
//! from the web ("café.txt", NFC) and the same name re-uploaded
//! from a NextCloud desktop client on macOS (round-tripped to
//! NFD: `e` + combining acute) lands as two distinct rows, both
//! visible in the listing, both pointing at the same blob.
//!
//! What this does:
//!
//! 1. Scans every non-trashed file row.
//! 2. For each row whose name ≠ NFC(name):
//!    - If no other row in the same `(folder_id, user_id)` already
//!      holds the NFC form → UPDATE the row's name to NFC.
//!    - If a collision exists with **same blob_hash**: trash the
//!      newer of the two (`is_trashed = true`, `trashed_at = NOW()`).
//!      User can restore from the trash UI if needed.
//!    - If a collision exists with **different blob_hash**: rename
//!      the newer row to `{nfc_name}.duplicate`, incrementing the
//!      suffix (`.duplicate-1`, `.duplicate-2`, …) until a free name
//!      is found. Preserves both files; user can inspect and resolve.
//!    - In both collision cases, the surviving (older) row's name
//!      is also normalized to NFC.
//!
//! Run:
//!   `cargo run --bin migrate-nfc-filenames -- --dry-run`
//!   `cargo run --bin migrate-nfc-filenames`
//!
//! Folder rows are NOT touched in this pass — trashing a folder
//! affects descendants; that pass is deferred to a follow-up.

use chrono::{DateTime, Utc};
use sqlx::{PgPool, Row};
use std::env;
use uuid::Uuid;

use oxicloud::domain::services::path_service::normalize_storage_name;

#[derive(Debug, Clone)]
struct FileRow {
    id: Uuid,
    folder_id: Option<Uuid>,
    user_id: Uuid,
    name: String,
    blob_hash: String,
    created_at: DateTime<Utc>,
}

#[derive(Default)]
struct Stats {
    scanned: u64,
    already_nfc: u64,
    normalized_in_place: u64,
    deduped_same_content: u64,
    renamed_duplicate: u64,
}

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let args: Vec<String> = env::args().collect();
    let dry_run = args.iter().any(|a| a == "--dry-run");

    let database_url =
        env::var("DATABASE_URL").expect("DATABASE_URL must be set in the environment");

    let pool = PgPool::connect(&database_url).await?;

    println!(
        "=== NFC filename migration ({}) ===",
        if dry_run {
            "DRY RUN — no writes"
        } else {
            "EXECUTING"
        }
    );
    println!();

    let rows = load_non_trashed_files(&pool).await?;
    println!("Loaded {} non-trashed file rows", rows.len());
    println!();

    let mut stats = Stats {
        scanned: rows.len() as u64,
        ..Default::default()
    };

    for row in &rows {
        let nfc_name = normalize_storage_name(&row.name);
        if nfc_name == row.name {
            stats.already_nfc += 1;
            continue;
        }

        // Row is in non-NFC form. Look for a collision in the same
        // (folder_id, user_id) scope, including rows that may also
        // be non-NFC but happen to normalize to the same NFC value.
        let collision = find_collision(&pool, row, &nfc_name).await?;

        match collision {
            None => {
                println!(
                    "NORMALIZE  {}  user={}  '{}' → '{}'",
                    row.id, row.user_id, row.name, nfc_name
                );
                if !dry_run {
                    sqlx::query("UPDATE storage.files SET name = $1 WHERE id = $2")
                        .bind(&nfc_name)
                        .bind(row.id)
                        .execute(&pool)
                        .await?;
                }
                stats.normalized_in_place += 1;
            }
            Some(other) => {
                // Pick winner/loser by `created_at` — older wins.
                let (older, newer) = if row.created_at <= other.created_at {
                    (row, &other)
                } else {
                    (&other, row)
                };

                if older.blob_hash == newer.blob_hash {
                    // Same content → trash the newer; promote older's
                    // name to NFC if it isn't already.
                    println!(
                        "DEDUP      newer={} (trash, same blob)  older={}  user={}  hash={}",
                        newer.id,
                        older.id,
                        older.user_id,
                        &older.blob_hash[..16.min(older.blob_hash.len())]
                    );
                    if !dry_run {
                        sqlx::query(
                            "UPDATE storage.files
                                SET is_trashed = TRUE,
                                    trashed_at = NOW()
                              WHERE id = $1",
                        )
                        .bind(newer.id)
                        .execute(&pool)
                        .await?;
                        normalize_survivor_name(&pool, older, &nfc_name).await?;
                    }
                    stats.deduped_same_content += 1;
                } else {
                    // Different content → rename newer to a free
                    // `{nfc_name}.duplicate[-N]`; promote older to NFC.
                    let disambiguated = find_free_duplicate_name(&pool, newer, &nfc_name).await?;
                    println!(
                        "RENAME     newer={} (different blob)  older={}  '{}' → '{}'",
                        newer.id, older.id, newer.name, disambiguated
                    );
                    if !dry_run {
                        sqlx::query("UPDATE storage.files SET name = $1 WHERE id = $2")
                            .bind(&disambiguated)
                            .bind(newer.id)
                            .execute(&pool)
                            .await?;
                        normalize_survivor_name(&pool, older, &nfc_name).await?;
                    }
                    stats.renamed_duplicate += 1;
                }
            }
        }
    }

    println!();
    println!("=== Summary ===");
    println!("  scanned                            : {}", stats.scanned);
    println!(
        "  already in NFC                     : {}",
        stats.already_nfc
    );
    println!(
        "  normalized in place (no collision) : {}",
        stats.normalized_in_place
    );
    println!(
        "  dedup-trashed (same content)       : {}",
        stats.deduped_same_content
    );
    println!(
        "  renamed to .duplicate              : {}",
        stats.renamed_duplicate
    );
    if dry_run {
        println!();
        println!("DRY RUN — no rows were written. Re-run without --dry-run to apply.");
    }

    Ok(())
}

async fn load_non_trashed_files(pool: &PgPool) -> Result<Vec<FileRow>, Box<dyn std::error::Error>> {
    let raw = sqlx::query(
        "SELECT id, folder_id, user_id, name, blob_hash, created_at
           FROM storage.files
          WHERE NOT is_trashed
          ORDER BY created_at",
    )
    .fetch_all(pool)
    .await?;

    let mut out = Vec::with_capacity(raw.len());
    for r in raw {
        out.push(FileRow {
            id: r.try_get("id")?,
            folder_id: r.try_get("folder_id")?,
            user_id: r.try_get("user_id")?,
            name: r.try_get("name")?,
            blob_hash: r.try_get("blob_hash")?,
            created_at: r.try_get("created_at")?,
        });
    }
    Ok(out)
}

/// Looks for a row in the same `(folder_id, user_id)` scope whose
/// CURRENT name equals `nfc_name`, excluding the row being processed.
/// The other row may itself be in non-NFC form whose normalized
/// representation happens to differ from `nfc_name`; the collision
/// check is intentionally based on stored bytes (matching the
/// UNIQUE-index semantics that this migration is repairing).
async fn find_collision(
    pool: &PgPool,
    row: &FileRow,
    nfc_name: &str,
) -> Result<Option<FileRow>, Box<dyn std::error::Error>> {
    let result = sqlx::query(
        "SELECT id, folder_id, user_id, name, blob_hash, created_at
           FROM storage.files
          WHERE name = $1
            AND user_id = $2
            AND ($3::uuid IS NULL AND folder_id IS NULL
                 OR folder_id = $3::uuid)
            AND id <> $4
            AND NOT is_trashed
          LIMIT 1",
    )
    .bind(nfc_name)
    .bind(row.user_id)
    .bind(row.folder_id)
    .bind(row.id)
    .fetch_optional(pool)
    .await?;

    Ok(result.map(|r| FileRow {
        id: r.get("id"),
        folder_id: r.get("folder_id"),
        user_id: r.get("user_id"),
        name: r.get("name"),
        blob_hash: r.get("blob_hash"),
        created_at: r.get("created_at"),
    }))
}

/// Finds a free name in the form `{nfc_name}.duplicate` or
/// `{nfc_name}.duplicate-N` for `N >= 1`, scoped to the row's
/// `(folder_id, user_id)`. Returns the first candidate that does
/// not currently exist as a non-trashed row.
async fn find_free_duplicate_name(
    pool: &PgPool,
    row: &FileRow,
    nfc_name: &str,
) -> Result<String, Box<dyn std::error::Error>> {
    let mut suffix: u32 = 0;
    loop {
        let candidate = if suffix == 0 {
            format!("{}.duplicate", nfc_name)
        } else {
            format!("{}.duplicate-{}", nfc_name, suffix)
        };

        let taken: bool = sqlx::query_scalar(
            "SELECT EXISTS(
                SELECT 1 FROM storage.files
                 WHERE name = $1
                   AND user_id = $2
                   AND ($3::uuid IS NULL AND folder_id IS NULL
                        OR folder_id = $3::uuid)
                   AND id <> $4
                   AND NOT is_trashed)",
        )
        .bind(&candidate)
        .bind(row.user_id)
        .bind(row.folder_id)
        .bind(row.id)
        .fetch_one(pool)
        .await?;

        if !taken {
            return Ok(candidate);
        }
        suffix = suffix.saturating_add(1);
        // Safety bound — should never trigger under realistic data.
        if suffix > 10_000 {
            return Err(format!(
                "Exhausted .duplicate-N suffixes for '{}' in scope (user={}, folder_id={:?})",
                nfc_name, row.user_id, row.folder_id
            )
            .into());
        }
    }
}

/// If the surviving (older) row's stored name is not yet in NFC,
/// UPDATE it now that the collision has been resolved.
async fn normalize_survivor_name(
    pool: &PgPool,
    survivor: &FileRow,
    nfc_name: &str,
) -> Result<(), Box<dyn std::error::Error>> {
    if survivor.name == nfc_name {
        return Ok(());
    }
    sqlx::query("UPDATE storage.files SET name = $1 WHERE id = $2")
        .bind(nfc_name)
        .bind(survivor.id)
        .execute(pool)
        .await?;
    Ok(())
}