-- +goose Up
-- Document revision ledger: immutable snapshots, Version/Revision, agent candidates, change reports.
-- Pointer columns use ledger_*/head_* to avoid colliding with freeform_documents.current_version_id.

CREATE TABLE IF NOT EXISTS document_content_blobs (
    content_sha256   CHAR(64) PRIMARY KEY,
    content_markdown TEXT NOT NULL,
    byte_size        BIGINT NOT NULL CHECK (byte_size >= 0),
    created_at       TIMESTAMPTZ NOT NULL DEFAULT now()
);

CREATE TABLE IF NOT EXISTS document_snapshots (
    id                 BIGSERIAL PRIMARY KEY,
    doc_id             TEXT NOT NULL,
    content_sha256     CHAR(64) NOT NULL REFERENCES document_content_blobs(content_sha256),
    parent_snapshot_id BIGINT REFERENCES document_snapshots(id),
    block_map          JSONB NOT NULL DEFAULT '[]'::jsonb,
    source_kind        TEXT NOT NULL,
    actor_user_id      BIGINT,
    actor_ref          TEXT NOT NULL DEFAULT '',
    actor_snapshot     JSONB NOT NULL DEFAULT '{}'::jsonb,
    source_run_id      TEXT NOT NULL DEFAULT '',
    created_at         TIMESTAMPTZ NOT NULL DEFAULT now(),
    CONSTRAINT chk_snapshot_source_kind CHECK (source_kind IN ('template','human','agent','agent_squad','migration','system'))
);

CREATE INDEX IF NOT EXISTS idx_document_snapshots_doc ON document_snapshots(doc_id, created_at);

CREATE TABLE IF NOT EXISTS document_versions (
    id                     BIGSERIAL PRIMARY KEY,
    doc_id                 TEXT NOT NULL,
    version_no             INT NOT NULL,
    status                 TEXT NOT NULL,
    origin_kind            TEXT NOT NULL,
    baseline_snapshot_id   BIGINT NOT NULL REFERENCES document_snapshots(id),
    head_snapshot_id       BIGINT NOT NULL REFERENCES document_snapshots(id),
    human_revision_count   INT NOT NULL DEFAULT 0,
    source_run_id          TEXT NOT NULL DEFAULT '',
    change_report_id       BIGINT,
    opened_at              TIMESTAMPTZ NOT NULL DEFAULT now(),
    sealed_at              TIMESTAMPTZ,
    CONSTRAINT uq_document_versions_doc_no UNIQUE (doc_id, version_no),
    CONSTRAINT chk_document_versions_status CHECK (status IN ('open','sealed')),
    CONSTRAINT chk_document_versions_origin CHECK (origin_kind IN ('template','agent','agent_squad','migration'))
);

CREATE UNIQUE INDEX IF NOT EXISTS uq_document_versions_one_open
    ON document_versions(doc_id) WHERE status = 'open';

CREATE TABLE IF NOT EXISTS document_change_events (
    id                 BIGSERIAL PRIMARY KEY,
    doc_id             TEXT NOT NULL,
    version_id         BIGINT NOT NULL REFERENCES document_versions(id),
    event_no           INT NOT NULL,
    from_snapshot_id   BIGINT REFERENCES document_snapshots(id),
    to_snapshot_id     BIGINT NOT NULL REFERENCES document_snapshots(id),
    change_kind        TEXT NOT NULL,
    actor_kind         TEXT NOT NULL,
    actor_user_id      BIGINT,
    actor_ref          TEXT NOT NULL DEFAULT '',
    actor_snapshot     JSONB NOT NULL DEFAULT '{}'::jsonb,
    change_set         JSONB NOT NULL DEFAULT '[]'::jsonb,
    edit_session_id    TEXT NOT NULL DEFAULT '',
    request_id         TEXT NOT NULL DEFAULT '',
    idempotency_key    TEXT NOT NULL,
    created_at         TIMESTAMPTZ NOT NULL DEFAULT now(),
    CONSTRAINT uq_document_change_events_doc_event UNIQUE (doc_id, event_no),
    CONSTRAINT uq_document_change_events_idemp UNIQUE (doc_id, idempotency_key),
    CONSTRAINT chk_change_kind CHECK (change_kind IN ('human_revision','agent_commit','agent_noop','import','restore_as_new')),
    CONSTRAINT chk_actor_kind CHECK (actor_kind IN ('human','agent','agent_squad','template','migration','system'))
);

CREATE TABLE IF NOT EXISTS document_change_reports (
    id                   BIGSERIAL PRIMARY KEY,
    doc_id               TEXT NOT NULL,
    from_snapshot_id     BIGINT NOT NULL REFERENCES document_snapshots(id),
    to_snapshot_id       BIGINT NOT NULL REFERENCES document_snapshots(id),
    schema_version       INT NOT NULL DEFAULT 1,
    summary              JSONB NOT NULL DEFAULT '[]'::jsonb,
    risk_level           TEXT NOT NULL,
    risk_items           JSONB NOT NULL DEFAULT '[]'::jsonb,
    project_impacts      JSONB NOT NULL DEFAULT '{}'::jsonb,
    document_impacts     JSONB NOT NULL DEFAULT '[]'::jsonb,
    open_questions       JSONB NOT NULL DEFAULT '[]'::jsonb,
    analysis_status      TEXT NOT NULL,
    model_snapshot       TEXT NOT NULL DEFAULT '',
    prompt_version       TEXT NOT NULL DEFAULT '',
    deterministic_facts  JSONB NOT NULL DEFAULT '{}'::jsonb,
    corrects_report_id   BIGINT REFERENCES document_change_reports(id),
    raw_json             TEXT NOT NULL DEFAULT '',
    created_at           TIMESTAMPTZ NOT NULL DEFAULT now(),
    CONSTRAINT chk_report_risk CHECK (risk_level IN ('low','medium','high','critical')),
    CONSTRAINT chk_report_analysis CHECK (analysis_status IN ('complete','fallback','unassessed','corrected'))
);

ALTER TABLE document_versions
    ADD CONSTRAINT fk_document_versions_change_report
    FOREIGN KEY (change_report_id) REFERENCES document_change_reports(id);

CREATE TABLE IF NOT EXISTS document_agent_candidates (
    id                   BIGSERIAL PRIMARY KEY,
    doc_id               TEXT NOT NULL,
    input_snapshot_id    BIGINT NOT NULL REFERENCES document_snapshots(id),
    output_snapshot_id   BIGINT REFERENCES document_snapshots(id),
    run_id               TEXT NOT NULL,
    proposal_id          TEXT NOT NULL DEFAULT '',
    status               TEXT NOT NULL,
    authorized_scope     TEXT NOT NULL DEFAULT '',
    quality_result       TEXT NOT NULL DEFAULT '',
    change_report_id     BIGINT REFERENCES document_change_reports(id),
    actor_kind           TEXT NOT NULL,
    actor_snapshot       JSONB NOT NULL DEFAULT '{}'::jsonb,
    created_at           TIMESTAMPTZ NOT NULL DEFAULT now(),
    decided_at           TIMESTAMPTZ,
    CONSTRAINT uq_document_agent_candidates_run UNIQUE (doc_id, run_id),
    CONSTRAINT chk_candidate_status CHECK (status IN ('ready','needs_confirmation','committed','rejected','stale','quality_failed')),
    CONSTRAINT chk_candidate_actor CHECK (actor_kind IN ('agent','agent_squad'))
);

ALTER TABLE document_records
    ADD COLUMN IF NOT EXISTS ledger_version_id BIGINT REFERENCES document_versions(id),
    ADD COLUMN IF NOT EXISTS head_snapshot_id BIGINT REFERENCES document_snapshots(id),
    ADD COLUMN IF NOT EXISTS head_revision_no INT NOT NULL DEFAULT 0,
    ADD COLUMN IF NOT EXISTS review_snapshot_id BIGINT REFERENCES document_snapshots(id),
    ADD COLUMN IF NOT EXISTS revision_schema_version INT NOT NULL DEFAULT 0,
    ADD COLUMN IF NOT EXISTS row_revision BIGINT NOT NULL DEFAULT 0;

-- Rename freeform legacy pointer to avoid semantic collision with ledger version id.
ALTER TABLE freeform_documents
    RENAME COLUMN current_version_id TO legacy_version_id;

ALTER TABLE freeform_documents
    ADD COLUMN IF NOT EXISTS ledger_version_id BIGINT REFERENCES document_versions(id),
    ADD COLUMN IF NOT EXISTS head_snapshot_id BIGINT REFERENCES document_snapshots(id),
    ADD COLUMN IF NOT EXISTS head_revision_no INT NOT NULL DEFAULT 0,
    ADD COLUMN IF NOT EXISTS revision_schema_version INT NOT NULL DEFAULT 0,
    ADD COLUMN IF NOT EXISTS row_revision BIGINT NOT NULL DEFAULT 0;

-- Prevent UPDATE/DELETE on immutable snapshot bodies via trigger.
-- +goose StatementBegin
CREATE OR REPLACE FUNCTION document_snapshots_immutable() RETURNS trigger AS $$
BEGIN
    RAISE EXCEPTION 'document_snapshots is immutable';
END;
$$ LANGUAGE plpgsql;
-- +goose StatementEnd

DROP TRIGGER IF EXISTS trg_document_snapshots_immutable ON document_snapshots;
CREATE TRIGGER trg_document_snapshots_immutable
    BEFORE UPDATE OR DELETE ON document_snapshots
    FOR EACH ROW EXECUTE FUNCTION document_snapshots_immutable();

-- +goose StatementBegin
CREATE OR REPLACE FUNCTION document_content_blobs_immutable() RETURNS trigger AS $$
BEGIN
    RAISE EXCEPTION 'document_content_blobs is immutable';
END;
$$ LANGUAGE plpgsql;
-- +goose StatementEnd

DROP TRIGGER IF EXISTS trg_document_content_blobs_immutable ON document_content_blobs;
CREATE TRIGGER trg_document_content_blobs_immutable
    BEFORE UPDATE OR DELETE ON document_content_blobs
    FOR EACH ROW EXECUTE FUNCTION document_content_blobs_immutable();

-- +goose Down
DROP TRIGGER IF EXISTS trg_document_content_blobs_immutable ON document_content_blobs;
DROP FUNCTION IF EXISTS document_content_blobs_immutable();
DROP TRIGGER IF EXISTS trg_document_snapshots_immutable ON document_snapshots;
DROP FUNCTION IF EXISTS document_snapshots_immutable();

ALTER TABLE freeform_documents
    DROP COLUMN IF EXISTS row_revision,
    DROP COLUMN IF EXISTS revision_schema_version,
    DROP COLUMN IF EXISTS head_revision_no,
    DROP COLUMN IF EXISTS head_snapshot_id,
    DROP COLUMN IF EXISTS ledger_version_id;

ALTER TABLE freeform_documents
    RENAME COLUMN legacy_version_id TO current_version_id;

ALTER TABLE document_records
    DROP COLUMN IF EXISTS row_revision,
    DROP COLUMN IF EXISTS revision_schema_version,
    DROP COLUMN IF EXISTS review_snapshot_id,
    DROP COLUMN IF EXISTS head_revision_no,
    DROP COLUMN IF EXISTS head_snapshot_id,
    DROP COLUMN IF EXISTS ledger_version_id;

ALTER TABLE document_versions DROP CONSTRAINT IF EXISTS fk_document_versions_change_report;

DROP TABLE IF EXISTS document_agent_candidates;
DROP TABLE IF EXISTS document_change_reports;
DROP TABLE IF EXISTS document_change_events;
DROP TABLE IF EXISTS document_versions;
DROP TABLE IF EXISTS document_snapshots;
DROP TABLE IF EXISTS document_content_blobs;