//! Local SQLite schema + migrations. The schema mirrors the note/label model so an
//! offline note can later sync 1:1 with the server. Each syncable row carries local
//! `sync_revision` + `dirty` bookkeeping (consumed by the sync engine in M10.7);
//! `#tags` are NOT stored as such (derived at query time into labels), matching
//! docs/sync.md.
//!
//! Migrations are gated on `PRAGMA user_version`; bump it and add a block per change.

use rusqlite::Connection;

const SCHEMA_V1: &str = r#"
CREATE TABLE notes (
    id           TEXT PRIMARY KEY,
    title        TEXT,
    body         TEXT NOT NULL DEFAULT '',
    color        TEXT NOT NULL DEFAULT 'default',
    kind         TEXT NOT NULL DEFAULT 'text',   -- 'text' | 'list'
    position     INTEGER NOT NULL DEFAULT 0,
    pinned       INTEGER NOT NULL DEFAULT 0,
    archived     INTEGER NOT NULL DEFAULT 0,
    trashed      INTEGER NOT NULL DEFAULT 0,
    remind_at    TEXT,
    recurrence   TEXT,
    created_at   TEXT NOT NULL,
    updated_at   TEXT NOT NULL,
    sync_revision INTEGER NOT NULL DEFAULT 0,
    dirty        INTEGER NOT NULL DEFAULT 1
);

CREATE TABLE labels (
    id           TEXT PRIMARY KEY,
    name         TEXT NOT NULL,
    color        TEXT NOT NULL DEFAULT 'default',
    created_at   TEXT NOT NULL,
    updated_at   TEXT NOT NULL,
    sync_revision INTEGER NOT NULL DEFAULT 0,
    dirty        INTEGER NOT NULL DEFAULT 1
);
CREATE UNIQUE INDEX idx_labels_name ON labels (lower(name));

CREATE TABLE note_labels (
    note_id  TEXT NOT NULL REFERENCES notes(id) ON DELETE CASCADE,
    label_id TEXT NOT NULL REFERENCES labels(id) ON DELETE CASCADE,
    via_tag  INTEGER NOT NULL DEFAULT 0,
    PRIMARY KEY (note_id, label_id)
);
CREATE INDEX idx_note_labels_label ON note_labels (label_id);

CREATE TABLE checklist_items (
    id        TEXT PRIMARY KEY,
    note_id   TEXT NOT NULL REFERENCES notes(id) ON DELETE CASCADE,
    text      TEXT NOT NULL DEFAULT '',
    checked   INTEGER NOT NULL DEFAULT 0,
    position  INTEGER NOT NULL DEFAULT 0
);
CREATE INDEX idx_items_note ON checklist_items (note_id);

CREATE TABLE attachments (
    id        TEXT PRIMARY KEY,
    note_id   TEXT NOT NULL REFERENCES notes(id) ON DELETE CASCADE,
    url       TEXT NOT NULL,
    filename  TEXT,
    mime      TEXT NOT NULL DEFAULT 'application/octet-stream',
    size      INTEGER,
    sha256    TEXT,
    position  INTEGER NOT NULL DEFAULT 0
);
CREATE INDEX idx_attachments_note ON attachments (note_id);

CREATE TABLE link_previews (
    id           TEXT PRIMARY KEY,
    note_id      TEXT NOT NULL REFERENCES notes(id) ON DELETE CASCADE,
    url          TEXT NOT NULL,
    title        TEXT,
    description  TEXT,
    image_url    TEXT,
    site_name    TEXT,
    position     INTEGER NOT NULL DEFAULT 0
);
CREATE INDEX idx_previews_note ON link_previews (note_id);

CREATE TABLE note_revisions (
    id         TEXT PRIMARY KEY,
    note_id    TEXT NOT NULL REFERENCES notes(id) ON DELETE CASCADE,
    title      TEXT,
    body       TEXT NOT NULL,
    created_at TEXT NOT NULL
);
CREATE INDEX idx_revisions_note ON note_revisions (note_id, created_at);

CREATE TABLE saved_filters (
    id         TEXT PRIMARY KEY,
    name       TEXT NOT NULL,
    params     TEXT NOT NULL DEFAULT '{}',   -- NoteFacets JSON
    position   INTEGER NOT NULL DEFAULT 0,
    created_at TEXT NOT NULL
);

-- Single-row sync bookkeeping (server URL / device token / last-consumed cursor).
CREATE TABLE sync_state (
    id            INTEGER PRIMARY KEY CHECK (id = 1),
    server_url    TEXT,
    device_token  TEXT,
    last_cursor   TEXT
);
INSERT INTO sync_state (id) VALUES (1);
"#;

// v2 (M10.7c): local tombstones.
//
// A permanent delete previously just dropped the row, which left NO record that it
// ever existed. Offline, that means the delete can never be pushed — and the next
// pull would faithfully resurrect the note from the server. A deletion that undoes
// itself is about the worst outcome sync can produce, so deletes are now recorded
// here until they've been acknowledged by the server and cleared.
const SCHEMA_V2: &str = r#"
CREATE TABLE pending_deletes (
    entity     TEXT NOT NULL,          -- 'note' | 'label'
    id         TEXT NOT NULL,
    deleted_at TEXT NOT NULL,
    PRIMARY KEY (entity, id)
);
"#;

// v3 (M10.7e): when the last successful sync finished.
//
// The cursor alone can't answer "is this up to date?" — it's a revision watermark,
// not a time, and it doesn't move at all when a sync legitimately finds nothing new.
// The UI needs a timestamp to say anything honest.
const SCHEMA_V3: &str = r#"
ALTER TABLE sync_state ADD COLUMN last_sync_at TEXT;
"#;

// v4 (M11.3): WHEN a note was trashed.
//
// The table only ever recorded THAT a note was trashed, which is enough to draw a
// Trash view and nothing else. Retention needs an age: without a timestamp there is
// no way to tell a note trashed this morning from one trashed last spring, so an
// offline device could never expire its own trash — and the UI couldn't warn anyone
// before it did.
// It also records the LINKED server's retention window, captured from /api/config.
// Once linked, the server's policy is the one that actually applies, so showing this
// device's offline default would put a countdown on screen that doesn't match what
// happens — a wrong deadline is worse than none.
const SCHEMA_V4: &str = r#"
ALTER TABLE notes ADD COLUMN trashed_at TEXT;
UPDATE notes SET trashed_at = updated_at WHERE trashed = 1;
ALTER TABLE sync_state ADD COLUMN server_retention_days INTEGER;
"#;

// v5 (M10.9): small key/value app preferences.
//
// The first entry is the update channel, which is neither note data nor part of the
// server link — so it belongs in neither `notes` nor `sync_state`. Generic on
// purpose: the next device-local preference shouldn't need another migration.
const SCHEMA_V5: &str = r#"
CREATE TABLE prefs (
    key   TEXT PRIMARY KEY,
    value TEXT NOT NULL
);
"#;

/// Bring the database up to the latest schema. Idempotent.
pub fn migrate(conn: &Connection) -> rusqlite::Result<()> {
    conn.execute_batch("PRAGMA foreign_keys = ON;")?;
    let version: i64 = conn.query_row("PRAGMA user_version", [], |r| r.get(0))?;
    if version < 1 {
        conn.execute_batch(SCHEMA_V1)?;
        conn.execute_batch("PRAGMA user_version = 1;")?;
    }
    if version < 2 {
        conn.execute_batch(SCHEMA_V2)?;
        conn.execute_batch("PRAGMA user_version = 2;")?;
    }
    if version < 3 {
        conn.execute_batch(SCHEMA_V3)?;
        conn.execute_batch("PRAGMA user_version = 3;")?;
    }
    if version < 4 {
        conn.execute_batch(SCHEMA_V4)?;
        conn.execute_batch("PRAGMA user_version = 4;")?;
    }
    if version < 5 {
        conn.execute_batch(SCHEMA_V5)?;
        conn.execute_batch("PRAGMA user_version = 5;")?;
    }
    Ok(())
}