//! SQLite-backed handle registry.

use std::path::Path;
use std::sync::Arc;

use chrono::{DateTime, Utc};
use kez_core::Identity;
use rusqlite::{Connection, OptionalExtension, params};
use tokio::sync::Mutex;

use crate::error::ApiError;

#[derive(Debug, Clone)]
pub struct HandleRecord {
    pub handle: String,
    pub primary: Identity,
    pub registered_at: DateTime<Utc>,
    /// JSON array of claim subjects the user has published to their profile
    /// (e.g. ["github:alice","dns:alice.com"]). Discovery only — peers
    /// independently verify each against the channel. None until set.
    pub proofs: Option<String>,
}

#[derive(Clone)]
pub struct Store {
    inner: Arc<Mutex<Connection>>,
}

impl Store {
    pub fn open(path: &Path) -> Result<Self, rusqlite::Error> {
        let conn = Connection::open(path)?;
        init_schema(&conn)?;
        Ok(Self {
            inner: Arc::new(Mutex::new(conn)),
        })
    }

    pub fn open_in_memory() -> Result<Self, rusqlite::Error> {
        let conn = Connection::open_in_memory()?;
        init_schema(&conn)?;
        Ok(Self {
            inner: Arc::new(Mutex::new(conn)),
        })
    }

    /// Reserve a handle for a primary key. Fails with Conflict if the
    /// handle is already taken, or if this primary key has already
    /// registered a (different) handle.
    pub async fn register(&self, record: &HandleRecord) -> Result<(), ApiError> {
        let conn = self.inner.lock().await;
        conn.execute(
            "INSERT INTO handles (handle, primary_id, registered_at)
             VALUES (?1, ?2, ?3)",
            params![
                record.handle,
                record.primary.to_string(),
                record.registered_at.to_rfc3339(),
            ],
        )
        .map_err(|e| match e {
            rusqlite::Error::SqliteFailure(err, _)
                if err.code == rusqlite::ErrorCode::ConstraintViolation =>
            {
                ApiError::Conflict("handle is already taken".into())
            }
            other => ApiError::Internal(format!("db: {other}")),
        })?;
        Ok(())
    }

    /// Look up the record for `handle`. Returns None if not registered.
    pub async fn lookup(&self, handle: &str) -> Result<Option<HandleRecord>, ApiError> {
        let conn = self.inner.lock().await;
        let row = conn
            .query_row(
                "SELECT handle, primary_id, registered_at, proofs
                 FROM handles WHERE handle = ?1",
                params![handle],
                row_to_record_parts,
            )
            .optional()?;
        row.map(build_record).transpose()
    }

    /// Replace the published proof-subject list for `handle`.
    pub async fn set_proofs(&self, handle: &str, proofs_json: &str) -> Result<(), ApiError> {
        let conn = self.inner.lock().await;
        let n = conn.execute(
            "UPDATE handles SET proofs = ?1 WHERE handle = ?2",
            params![proofs_json, handle],
        )?;
        if n == 0 {
            return Err(ApiError::NotFound);
        }
        Ok(())
    }

    /// Look up the record for a primary key — used by the NATS auth
    /// callout: NATS sends us a connecting client's nkey, we figure out
    /// which handle (if any) owns it.
    pub async fn lookup_by_primary(
        &self,
        primary: &Identity,
    ) -> Result<Option<HandleRecord>, ApiError> {
        let conn = self.inner.lock().await;
        let row = conn
            .query_row(
                "SELECT handle, primary_id, registered_at, proofs
                 FROM handles WHERE primary_id = ?1",
                params![primary.to_string()],
                row_to_record_parts,
            )
            .optional()?;
        row.map(build_record).transpose()
    }
}

type RecordParts = (String, String, String, Option<String>);

fn row_to_record_parts(row: &rusqlite::Row) -> rusqlite::Result<RecordParts> {
    Ok((row.get(0)?, row.get(1)?, row.get(2)?, row.get(3)?))
}

fn build_record(parts: RecordParts) -> Result<HandleRecord, ApiError> {
    let (handle, primary_id, registered_at, proofs) = parts;
    let primary = Identity::parse(primary_id)
        .map_err(|e| ApiError::Internal(format!("stored primary not parseable: {e}")))?;
    let registered_at = DateTime::parse_from_rfc3339(&registered_at)
        .map_err(|e| ApiError::Internal(format!("stored timestamp not parseable: {e}")))?
        .with_timezone(&Utc);
    Ok(HandleRecord {
        handle,
        primary,
        registered_at,
        proofs,
    })
}

fn init_schema(conn: &Connection) -> Result<(), rusqlite::Error> {
    // New column for existing databases — ignore "duplicate column" so
    // re-running on an already-migrated DB is a no-op.
    let _ = conn.execute("ALTER TABLE handles ADD COLUMN proofs TEXT", []);

    conn.execute_batch(
        "CREATE TABLE IF NOT EXISTS handles (
            handle        TEXT NOT NULL PRIMARY KEY,
            primary_id    TEXT NOT NULL UNIQUE,
            registered_at TEXT NOT NULL,
            proofs        TEXT
         );
         CREATE INDEX IF NOT EXISTS idx_handles_primary
            ON handles (primary_id);

         -- Opaque encrypted-envelope mailbox. The server can't read these;
         -- it's a dumb relay that stores blobs addressed to a handle and
         -- hands them back when the handle's owner authenticates a poll.
         CREATE TABLE IF NOT EXISTS messages (
            seq               INTEGER PRIMARY KEY AUTOINCREMENT,
            recipient_handle  TEXT NOT NULL,
            envelope          TEXT NOT NULL,
            created_at        TEXT NOT NULL
         );
         CREATE INDEX IF NOT EXISTS idx_messages_recipient
            ON messages (recipient_handle, seq);",
    )
}

// ─────────────────────────────────────────────────────────────────────────────
// Messages (opaque encrypted envelopes, server-side dumb relay)
// ─────────────────────────────────────────────────────────────────────────────

/// One stored envelope. The server doesn't introspect the envelope JSON —
/// recipients decrypt it client-side. We surface only what's needed for
/// addressing + ordering: `seq`, when we received it, and the raw blob.
#[derive(Debug, Clone)]
pub struct StoredMessage {
    pub seq: i64,
    pub envelope: String,
    pub created_at: DateTime<Utc>,
}

impl Store {
    /// Append an envelope to `recipient`'s mailbox. Returns the assigned seq.
    pub async fn store_message(
        &self,
        recipient: &str,
        envelope: &str,
    ) -> Result<i64, ApiError> {
        let now = Utc::now().to_rfc3339();
        let conn = self.inner.lock().await;
        conn.execute(
            "INSERT INTO messages (recipient_handle, envelope, created_at)
             VALUES (?1, ?2, ?3)",
            params![recipient, envelope, now],
        )?;
        Ok(conn.last_insert_rowid())
    }

    /// Pull envelopes for `recipient` with `seq > since`, oldest first.
    /// `limit` caps the response so a long-offline user can't blow up a
    /// single poll — the client paginates by re-calling with the new max seq.
    pub async fn inbox(
        &self,
        recipient: &str,
        since: i64,
        limit: i64,
    ) -> Result<Vec<StoredMessage>, ApiError> {
        let conn = self.inner.lock().await;
        let mut stmt = conn.prepare(
            "SELECT seq, envelope, created_at
             FROM messages
             WHERE recipient_handle = ?1 AND seq > ?2
             ORDER BY seq ASC
             LIMIT ?3",
        )?;
        let rows = stmt
            .query_map(params![recipient, since, limit], |row| {
                let seq: i64 = row.get(0)?;
                let envelope: String = row.get(1)?;
                let created_at: String = row.get(2)?;
                Ok((seq, envelope, created_at))
            })?
            .collect::<Result<Vec<_>, _>>()?;

        let mut out = Vec::with_capacity(rows.len());
        for (seq, envelope, created_at) in rows {
            let created_at = DateTime::parse_from_rfc3339(&created_at)
                .map_err(|e| {
                    ApiError::Internal(format!("stored message ts not parseable: {e}"))
                })?
                .with_timezone(&Utc);
            out.push(StoredMessage {
                seq,
                envelope,
                created_at,
            });
        }
        Ok(out)
    }
}