-- Multiple conversations per persona.
--
-- v1 keyed a transcript on (user_id, persona_id), so a persona had exactly
-- one rolling conversation and there was no way to start a fresh topic
-- without discarding the old one. The key is now an opaque `conversation_id`,
-- with (user_id, persona_id) demoted to an index.
--
-- `title` is a short generated summary of the opening exchange, used as the
-- conversation's name in the list. Empty until the first turn completes; the
-- client falls back to the persona name while it is blank.
--
-- SQLite cannot redefine a primary key in place, so this is the standard
-- create-copy-drop-rename dance. Existing transcripts carry over with a
-- generated id and an empty title.

CREATE TABLE persona_chat_conversations_new (
    conversation_id TEXT NOT NULL PRIMARY KEY,
    user_id INTEGER NOT NULL,
    persona_id TEXT NOT NULL,
    title TEXT NOT NULL DEFAULT '',
    messages_json TEXT NOT NULL DEFAULT '[]',
    turn_count INTEGER NOT NULL DEFAULT 0,
    created_at BIGINT NOT NULL,
    updated_at BIGINT NOT NULL
);

INSERT INTO persona_chat_conversations_new (
    conversation_id, user_id, persona_id, title,
    messages_json, turn_count, created_at, updated_at
)
SELECT
    lower(hex(randomblob(16))),
    user_id,
    persona_id,
    '',
    messages_json,
    turn_count,
    updated_at,
    updated_at
FROM persona_chat_conversations;

DROP INDEX IF EXISTS idx_persona_chat_updated;
DROP TABLE persona_chat_conversations;
ALTER TABLE persona_chat_conversations_new RENAME TO persona_chat_conversations;

CREATE INDEX idx_persona_chat_updated
    ON persona_chat_conversations (user_id, updated_at DESC);

CREATE INDEX idx_persona_chat_persona
    ON persona_chat_conversations (user_id, persona_id);