package db

import (
	"context"
	"database/sql"
	"log/slog"
	"strings"

	_ "github.com/mattn/go-sqlite3"
	"tangled.org/core/log"
	"tangled.org/core/orm"
)

type DB struct {
	*sql.DB
	logger *slog.Logger
}

type Execer interface {
	Query(query string, args ...any) (*sql.Rows, error)
	QueryContext(ctx context.Context, query string, args ...any) (*sql.Rows, error)
	QueryRow(query string, args ...any) *sql.Row
	QueryRowContext(ctx context.Context, query string, args ...any) *sql.Row
	Exec(query string, args ...any) (sql.Result, error)
	ExecContext(ctx context.Context, query string, args ...any) (sql.Result, error)
	Prepare(query string) (*sql.Stmt, error)
	PrepareContext(ctx context.Context, query string) (*sql.Stmt, error)
}

func Make(ctx context.Context, dbPath string) (*DB, error) {
	// https://github.com/mattn/go-sqlite3#connection-string
	opts := []string{
		"_foreign_keys=1",
		"_journal_mode=WAL",
		"_synchronous=NORMAL",
		"_auto_vacuum=incremental",
		"_busy_timeout=5000",
	}

	logger := log.FromContext(ctx)
	logger = log.SubLogger(logger, "db")

	db, err := sql.Open("sqlite3", dbPath+"?"+strings.Join(opts, "&"))
	if err != nil {
		return nil, err
	}

	conn, err := db.Conn(ctx)
	if err != nil {
		return nil, err
	}
	defer conn.Close()

	_, err = conn.ExecContext(ctx, `
		create table if not exists registrations (
			id integer primary key autoincrement,
			domain text not null unique,
			did text not null,
			secret text not null,
			created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),
			registered text
		);
		create table if not exists public_keys (
			id integer primary key autoincrement,
			did text not null,
			name text not null,
			key text not null,
			created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),
			unique(did, name, key)
		);
		create table if not exists repos (
			id integer primary key autoincrement,
			did text not null,
			name text not null,
			knot text not null,
			rkey text not null,
			at_uri text not null unique,
			created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),
			unique(did, name, knot, rkey)
		);
		create table if not exists collaborators (
			id integer primary key autoincrement,
			did text not null,
			repo integer not null,
			foreign key (repo) references repos(id) on delete cascade
		);
		create table if not exists follows (
			user_did text not null,
			subject_did text not null,
			rkey text not null,
			followed_at text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),
			primary key (user_did, subject_did),
			check (user_did <> subject_did)
		);
		create table if not exists issues (
			id integer primary key autoincrement,
			owner_did text not null,
			repo_at text not null,
			issue_id integer not null,
			title text not null,
			body text not null,
			open integer not null default 1,
			created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),
			issue_at text,
			unique(repo_at, issue_id),
			foreign key (repo_at) references repos(at_uri) on delete cascade
		);
		create table if not exists comments (
			id integer primary key autoincrement,
			owner_did text not null,
			issue_id integer not null,
			repo_at text not null,
			comment_id integer not null,
			comment_at text not null,
			body text not null,
			created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),
			unique(issue_id, comment_id),
			foreign key (repo_at, issue_id) references issues(repo_at, issue_id) on delete cascade
		);
		create table if not exists pulls (
			-- identifiers
			id integer primary key autoincrement,
			pull_id integer not null,

			-- at identifiers
			repo_at text not null,
			owner_did text not null,
			rkey text not null,
			pull_at text,

			-- content
			title text not null,
			body text not null,
			target_branch text not null,
			state integer not null default 0 check (state in (0, 1, 2)), -- open, merged, closed

			-- meta
			created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),

			-- constraints
			unique(repo_at, pull_id),
			foreign key (repo_at) references repos(at_uri) on delete cascade
		);

		-- every pull must have atleast 1 submission: the initial submission
		create table if not exists pull_submissions (
			-- identifiers
			id integer primary key autoincrement,
			pull_id integer not null,

			-- at identifiers
			repo_at text not null,

			-- content, these are immutable, and require a resubmission to update
			round_number integer not null default 0,
			patch text,

			-- meta
			created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),

			-- constraints
			unique(repo_at, pull_id, round_number),
			foreign key (repo_at, pull_id) references pulls(repo_at, pull_id) on delete cascade
		);

		create table if not exists pull_comments (
			-- identifiers
			id integer primary key autoincrement,
			pull_id integer not null,
			submission_id integer not null,

			-- at identifiers
			repo_at text not null,
			owner_did text not null,
			comment_at text not null,

			-- content
			body text not null,

			-- meta
			created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),

			-- constraints
			foreign key (repo_at, pull_id) references pulls(repo_at, pull_id) on delete cascade,
			foreign key (submission_id) references pull_submissions(id) on delete cascade
		);

		create table if not exists _jetstream (
			id integer primary key autoincrement,
			last_time_us integer not null
		);

		create table if not exists repo_issue_seqs (
			repo_at text primary key,
			next_issue_id integer not null default 1
		);

		create table if not exists repo_pull_seqs (
			repo_at text primary key,
			next_pull_id integer not null default 1
		);

		create table if not exists stars (
			id integer primary key autoincrement,
			starred_by_did text not null,
			repo_at text not null,
			rkey text not null,
			created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),
			foreign key (repo_at) references repos(at_uri) on delete cascade,
			unique(starred_by_did, repo_at)
		);

		create table if not exists reactions (
			id integer primary key autoincrement,
			reacted_by_did text not null,
			thread_at text not null,
			kind text not null,
			rkey text not null,
			created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),
			unique(reacted_by_did, thread_at, kind)
		);

		create table if not exists emails (
			id integer primary key autoincrement,
			did text not null,
			email text not null,
			verified integer not null default 0,
			verification_code text not null,
			last_sent text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),
			is_primary integer not null default 0,
			created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),
			unique(did, email)
		);

		create table if not exists artifacts (
			-- id
			id integer primary key autoincrement,
			did text not null,
			rkey text not null,

			-- meta
			repo_at text not null,
			tag binary(20) not null,
			created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),

			-- data
			blob_cid text not null,
			name text not null,
			size integer not null default 0,
			mimetype string not null default "*/*",

			-- constraints
			unique(did, rkey),          -- record must be unique
			unique(repo_at, tag, name), -- for a given tag object, each file must be unique
			foreign key (repo_at) references repos(at_uri) on delete cascade
		);

		create table if not exists profile (
			-- id
			id integer primary key autoincrement,
			did text not null,

			-- data
			avatar text,
			description text not null,
			include_bluesky integer not null default 0,
			location text,

			-- constraints
			unique(did)
		);
		create table if not exists profile_links (
			-- id
			id integer primary key autoincrement,
			did text not null,

			-- data
			link text not null,

			-- constraints
			foreign key (did) references profile(did) on delete cascade
		);
		create table if not exists profile_stats (
			-- id
			id integer primary key autoincrement,
			did text not null,

			-- data
			kind text not null check (kind in (
				"merged-pull-request-count",
				"closed-pull-request-count",
				"open-pull-request-count",
				"open-issue-count",
				"closed-issue-count",
				"repository-count"
			)),

			-- constraints
			foreign key (did) references profile(did) on delete cascade
		);
		create table if not exists profile_pinned_repositories (
			-- id
			id integer primary key autoincrement,
			did text not null,

			-- data
			at_uri text not null,

			-- constraints
			unique(did, at_uri),
			foreign key (did) references profile(did) on delete cascade,
			foreign key (at_uri) references repos(at_uri) on delete cascade
		);

		create table if not exists oauth_requests (
			id integer primary key autoincrement,
			auth_server_iss text not null,
			state text not null,
			did text not null,
			handle text not null,
			pds_url text not null,
			pkce_verifier text not null,
			dpop_auth_server_nonce text not null,
			dpop_private_jwk text not null
		);

		create table if not exists oauth_sessions (
			id integer primary key autoincrement,
			did text not null,
			handle text not null,
			pds_url text not null,
			auth_server_iss text not null,
			access_jwt text not null,
			refresh_jwt text not null,
			dpop_pds_nonce text,
			dpop_auth_server_nonce text not null,
			dpop_private_jwk text not null,
			expiry text not null
		);

		create table if not exists punchcard (
			did text not null,
			date text not null, -- yyyy-mm-dd
			count integer,
			primary key (did, date)
		);

		create table if not exists spindles (
			id integer primary key autoincrement,
			owner text not null,
			instance text not null,
			verified text, -- time of verification
			created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),

			unique(owner, instance)
		);

		create table if not exists spindle_members (
			-- identifiers for the record
			id integer primary key autoincrement,
			did text not null,
			rkey text not null,

			-- data
			instance text not null,
			subject text not null,
			created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),

			-- constraints
			unique (did, instance, subject)
		);

		create table if not exists pipelines (
			-- identifiers
			id integer primary key autoincrement,
			knot text not null,
			rkey text not null,

			repo_owner text not null,
			repo_name text not null,

			-- every pipeline must be associated with exactly one commit
			sha text not null check (length(sha) = 40),
			created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),

			-- trigger data
			trigger_id integer not null,

			unique(knot, rkey),
			foreign key (trigger_id) references triggers(id) on delete cascade
		);

		create table if not exists triggers (
			-- primary key
			id integer primary key autoincrement,

			-- top-level fields
			kind text not null,

			-- pushTriggerData fields
			push_ref text,
			push_new_sha text check (length(push_new_sha) = 40),
			push_old_sha text check (length(push_old_sha) = 40),

			-- pullRequestTriggerData fields
			pr_source_branch text,
			pr_target_branch text,
			pr_source_sha text check (length(pr_source_sha) = 40),
			pr_action text
		);

		create table if not exists pipeline_statuses (
			-- identifiers
			id integer primary key autoincrement,
			spindle text not null,
			rkey text not null,

			-- referenced pipeline. these form the (did, rkey) pair
			pipeline_knot text not null,
			pipeline_rkey text not null,

			-- content
			created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),
			workflow text not null,
			status text not null,
			error text,
			exit_code integer not null default 0,

			unique (spindle, rkey),
			foreign key (pipeline_knot, pipeline_rkey)
				references pipelines (knot, rkey)
				on delete cascade
		);

		create table if not exists repo_languages (
			-- identifiers
			id integer primary key autoincrement,

			-- repo identifiers
			repo_at text not null,
			ref text not null,
			is_default_ref integer not null default 0,

			-- language breakdown
			language text not null,
			bytes integer not null check (bytes >= 0),

			unique(repo_at, ref, language)
		);

		create table if not exists signups_inflight (
			id integer primary key autoincrement,
			email text not null unique,
			invite_code text not null,
			created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now'))
		);

		create table if not exists strings (
			-- identifiers
			did text not null,
			rkey text not null,

			-- content
			filename text not null,
			description text,
			content text not null,
			created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),
			edited text,

			primary key (did, rkey)
		);

		create table if not exists label_definitions (
			-- identifiers
			id integer primary key autoincrement,
			did text not null,
			rkey text not null,
			at_uri text generated always as ('at://' || did || '/' || 'sh.tangled.label.definition' || '/' || rkey) stored,

			-- content
			name text not null,
			value_type text not null check (value_type in (
				"null",
				"boolean",
				"integer",
				"string"
			)),
			value_format text not null default "any",
			value_enum text, -- comma separated list
			scope text not null, -- comma separated list of nsid
			color text,
			multiple integer not null default 0,
			created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),

			-- constraints
			unique (did, rkey)
			unique (at_uri)
		);

		-- ops are flattened, a record may contain several additions and deletions, but the table will include one row per add/del
		create table if not exists label_ops (
			-- identifiers
			id integer primary key autoincrement,
			did text not null,
			rkey text not null,
			at_uri text generated always as ('at://' || did || '/' || 'sh.tangled.label.op' || '/' || rkey) stored,

			-- content
			subject text not null,
			operation text not null check (operation in ("add", "del")),
			operand_key text not null,
			operand_value text not null,
			-- we need two time values: performed is declared by the user, indexed is calculated by the av
			performed text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),
			indexed text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),

			-- constraints
			-- traditionally (did, rkey) pair should be unique, but not in this case
			-- operand_key should reference a label definition
			foreign key (operand_key) references label_definitions (at_uri) on delete cascade,
			unique (did, rkey, subject, operand_key, operand_value)
		);

		create table if not exists repo_labels (
			-- identifiers
			id integer primary key autoincrement,

			-- repo identifiers
			repo_at text not null,

			-- label to subscribe to
			label_at text not null,

			unique (repo_at, label_at)
		);

		create table if not exists notifications (
			id integer primary key autoincrement,
			recipient_did text not null,
			actor_did text not null,
			type text not null,
			entity_type text not null,
			entity_id text not null,
			read integer not null default 0,
			created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),
			repo_id integer references repos(id),
			issue_id integer references issues(id),
			pull_id integer references pulls(id)
		);

		create table if not exists notification_preferences (
			id integer primary key autoincrement,
			user_did text not null unique,
			repo_starred integer not null default 1,
			issue_created integer not null default 1,
			issue_commented integer not null default 1,
			pull_created integer not null default 1,
			pull_commented integer not null default 1,
			followed integer not null default 1,
			pull_merged integer not null default 1,
			issue_closed integer not null default 1,
			email_notifications integer not null default 0
		);

		create table if not exists reference_links (
			id integer primary key autoincrement,
			from_at text not null,
			to_at text not null,
			unique (from_at, to_at)
		);

		create table if not exists webhooks (
			id integer primary key autoincrement,
			repo_at text not null,
			url text not null,
			secret text,
			active integer not null default 1,
			events text not null, -- comma-separated list of events
			created_at text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),
			updated_at text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),

			foreign key (repo_at) references repos(at_uri) on delete cascade
		);

		create table if not exists webhook_deliveries (
			id integer primary key autoincrement,
			webhook_id integer not null,
			event text not null,
			delivery_id text not null,
			url text not null,
			request_body text not null,
			response_code integer,
			response_body text,
			success integer not null default 0,
			created_at text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),

			foreign key (webhook_id) references webhooks(id) on delete cascade
		);

		create table if not exists bluesky_posts (
			rkey text primary key,
			text text not null,
			created_at text not null,
			langs text,
			facets text,
			embed text,
			like_count integer not null default 0,
			reply_count integer not null default 0,
			repost_count integer not null default 0,
			quote_count integer not null default 0
		);

		create table if not exists domain_claims (
			id integer primary key autoincrement,
			did text not null unique,
			domain text not null unique,
			deleted text -- timestamp when the domain was released/unclaimed; null means actively claimed
		);

		create table if not exists repo_sites (
			id integer primary key autoincrement,
			repo_at text not null unique,
			branch text not null,
			dir text not null default '/',
			is_index integer not null default 0,
			created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),
			updated text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),
			foreign key (repo_at) references repos(at_uri) on delete cascade
		);

		create table if not exists site_deploys (
			id integer primary key autoincrement,
			repo_at text not null,
			branch text not null,
			dir text not null default '/',
			commit_sha text not null default '',
			status text not null check (status in ('success', 'failure')),
			trigger text not null check (trigger in ('config_change', 'push')),
			error text not null default '',
			created_at text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),
			foreign key (repo_at) references repos(at_uri) on delete cascade
		);

		create table if not exists migrations (
			id integer primary key autoincrement,
			name text unique
		);

		create table if not exists punchcard_preferences (
			id integer primary key autoincrement,
			user_did text not null unique,
			hide_mine integer default 0,
			hide_others integer default 0
		);

		-- indexes for better performance
		create index if not exists idx_notifications_recipient_created on notifications(recipient_did, created desc);
		create index if not exists idx_notifications_recipient_read on notifications(recipient_did, read);
		create index if not exists idx_references_from_at on reference_links(from_at);
		create index if not exists idx_references_to_at on reference_links(to_at);
		create index if not exists idx_webhooks_repo_at on webhooks(repo_at);
		create index if not exists idx_webhook_deliveries_webhook_id on webhook_deliveries(webhook_id);
		create index if not exists idx_site_deploys_repo_at on site_deploys(repo_at);
	`)
	if err != nil {
		return nil, err
	}

	// run migrations
	orm.RunMigration(conn, logger, "add-description-to-repos", func(tx *sql.Tx) error {
		tx.Exec(`
			alter table repos add column description text check (length(description) <= 200);
		`)
		return nil
	})

	orm.RunMigration(conn, logger, "add-rkey-to-pubkeys", func(tx *sql.Tx) error {
		// add unconstrained column
		_, err := tx.Exec(`
			alter table public_keys
			add column rkey text;
		`)
		if err != nil {
			return err
		}

		// backfill
		_, err = tx.Exec(`
			update public_keys
			set rkey = ''
			where rkey is null;
		`)
		if err != nil {
			return err
		}

		return nil
	})

	orm.RunMigration(conn, logger, "add-rkey-to-comments", func(tx *sql.Tx) error {
		_, err := tx.Exec(`
			alter table comments drop column comment_at;
			alter table comments add column rkey text;
		`)
		return err
	})

	orm.RunMigration(conn, logger, "add-deleted-and-edited-to-issue-comments", func(tx *sql.Tx) error {
		_, err := tx.Exec(`
			alter table comments add column deleted text; -- timestamp
			alter table comments add column edited text; -- timestamp
		`)
		return err
	})

	orm.RunMigration(conn, logger, "add-source-info-to-pulls-and-submissions", func(tx *sql.Tx) error {
		_, err := tx.Exec(`
			alter table pulls add column source_branch text;
			alter table pulls add column source_repo_at text;
			alter table pull_submissions add column source_rev text;
		`)
		return err
	})

	orm.RunMigration(conn, logger, "add-source-to-repos", func(tx *sql.Tx) error {
		_, err := tx.Exec(`
			alter table repos add column source text;
		`)
		return err
	})

	// disable foreign-keys for the next migration
	// NOTE: this cannot be done in a transaction, so it is run outside [0]
	//
	// [0]: https://sqlite.org/pragma.html#pragma_foreign_keys
	conn.ExecContext(ctx, "pragma foreign_keys = off;")
	orm.RunMigration(conn, logger, "recreate-pulls-column-for-stacking-support", func(tx *sql.Tx) error {
		_, err := tx.Exec(`
			create table pulls_new (
				-- identifiers
				id integer primary key autoincrement,
				pull_id integer not null,

				-- at identifiers
				repo_at text not null,
				owner_did text not null,
				rkey text not null,

				-- content
				title text not null,
				body text not null,
				target_branch text not null,
				state integer not null default 0 check (state in (0, 1, 2, 3)), -- closed, open, merged, deleted

				-- source info
				source_branch text,
				source_repo_at text,

				-- stacking
				stack_id text,
				change_id text,
				parent_change_id text,

				-- meta
				created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),

				-- constraints
				unique(repo_at, pull_id),
				foreign key (repo_at) references repos(at_uri) on delete cascade
			);

			insert into pulls_new (
				id, pull_id,
				repo_at, owner_did, rkey,
				title, body, target_branch, state,
				source_branch, source_repo_at,
				created
			)
			select
				id, pull_id,
				repo_at, owner_did, rkey,
				title, body, target_branch, state,
				source_branch, source_repo_at,
				created
			FROM pulls;

			drop table pulls;
			alter table pulls_new rename to pulls;
		`)
		return err
	})
	conn.ExecContext(ctx, "pragma foreign_keys = on;")

	orm.RunMigration(conn, logger, "add-spindle-to-repos", func(tx *sql.Tx) error {
		tx.Exec(`
			alter table repos add column spindle text;
		`)
		return nil
	})

	// drop all knot secrets, add unique constraint to knots
	//
	// knots will henceforth use service auth for signed requests
	orm.RunMigration(conn, logger, "no-more-secrets", func(tx *sql.Tx) error {
		_, err := tx.Exec(`
			create table registrations_new (
				id integer primary key autoincrement,
				domain text not null,
				did text not null,
				created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),
				registered text,
				read_only integer not null default 0,
				unique(domain, did)
			);

			insert into registrations_new (id, domain, did, created, registered, read_only)
			select id, domain, did, created, registered, 1 from registrations
			where registered is not null;

			drop table registrations;
			alter table registrations_new rename to registrations;
		`)
		return err
	})

	// recreate and add rkey + created columns with default constraint
	orm.RunMigration(conn, logger, "rework-collaborators-table", func(tx *sql.Tx) error {
		// create new table
		// - repo_at instead of repo integer
		// - rkey field
		// - created field
		_, err := tx.Exec(`
			create table collaborators_new (
				-- identifiers for the record
				id integer primary key autoincrement,
				did text not null,
				rkey text,

				-- content
				subject_did text not null,
				repo_at text not null,

				-- meta
				created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),

				-- constraints
				foreign key (repo_at) references repos(at_uri) on delete cascade
			)
		`)
		if err != nil {
			return err
		}

		// copy data
		_, err = tx.Exec(`
			insert into collaborators_new (id, did, rkey, subject_did, repo_at)
			select
				c.id,
				r.did,
				'',
				c.did,
				r.at_uri
			from collaborators c
			join repos r on c.repo = r.id
		`)
		if err != nil {
			return err
		}

		// drop old table
		_, err = tx.Exec(`drop table collaborators`)
		if err != nil {
			return err
		}

		// rename new table
		_, err = tx.Exec(`alter table collaborators_new rename to collaborators`)
		return err
	})

	orm.RunMigration(conn, logger, "add-rkey-to-issues", func(tx *sql.Tx) error {
		_, err := tx.Exec(`
			alter table issues add column rkey text not null default '';

			-- get last url section from issue_at and save to rkey column
			update issues
			set rkey = replace(issue_at, rtrim(issue_at, replace(issue_at, '/', '')), '');
		`)
		return err
	})

	// repurpose the read-only column to "needs-upgrade"
	orm.RunMigration(conn, logger, "rename-registrations-read-only-to-needs-upgrade", func(tx *sql.Tx) error {
		_, err := tx.Exec(`
			alter table registrations rename column read_only to needs_upgrade;
		`)
		return err
	})

	// require all knots to upgrade after the release of total xrpc
	orm.RunMigration(conn, logger, "migrate-knots-to-total-xrpc", func(tx *sql.Tx) error {
		_, err := tx.Exec(`
			update registrations set needs_upgrade = 1;
		`)
		return err
	})

	// require all knots to upgrade after the release of total xrpc
	orm.RunMigration(conn, logger, "migrate-spindles-to-xrpc-owner", func(tx *sql.Tx) error {
		_, err := tx.Exec(`
			alter table spindles add column needs_upgrade integer not null default 0;
		`)
		return err
	})

	// remove issue_at from issues and replace with generated column
	//
	// this requires a full table recreation because stored columns
	// cannot be added via alter
	//
	// couple other changes:
	// - columns renamed to be more consistent
	// - adds edited and deleted fields
	//
	// disable foreign-keys for the next migration
	conn.ExecContext(ctx, "pragma foreign_keys = off;")
	orm.RunMigration(conn, logger, "remove-issue-at-from-issues", func(tx *sql.Tx) error {
		_, err := tx.Exec(`
			create table if not exists issues_new (
				-- identifiers
				id integer primary key autoincrement,
				did text not null,
				rkey text not null,
				at_uri text generated always as ('at://' || did || '/' || 'sh.tangled.repo.issue' || '/' || rkey) stored,

				-- at identifiers
				repo_at text not null,

				-- content
				issue_id integer not null,
				title text not null,
				body text not null,
				open integer not null default 1,
				created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),
				edited text,  -- timestamp
				deleted text,  -- timestamp

				unique(did, rkey),
				unique(repo_at, issue_id),
				unique(at_uri),
				foreign key (repo_at) references repos(at_uri) on delete cascade
			);
		`)
		if err != nil {
			return err
		}

		// transfer data
		_, err = tx.Exec(`
			insert into issues_new (id, did, rkey, repo_at, issue_id, title, body, open, created)
			select
				i.id,
				i.owner_did,
				i.rkey,
				i.repo_at,
				i.issue_id,
				i.title,
				i.body,
				i.open,
				i.created
			from issues i;
		`)
		if err != nil {
			return err
		}

		// drop old table
		_, err = tx.Exec(`drop table issues`)
		if err != nil {
			return err
		}

		// rename new table
		_, err = tx.Exec(`alter table issues_new rename to issues`)
		return err
	})
	conn.ExecContext(ctx, "pragma foreign_keys = on;")

	// - renames the comments table to 'issue_comments'
	// - rework issue comments to update constraints:
	//   * unique(did, rkey)
	//   * remove comment-id and just use the global ID
	//   * foreign key (repo_at, issue_id)
	// - new columns
	//   * column "reply_to" which can be any other comment
	//   * column "at-uri" which is a generated column
	orm.RunMigration(conn, logger, "rework-issue-comments", func(tx *sql.Tx) error {
		_, err := tx.Exec(`
			create table if not exists issue_comments (
				-- identifiers
				id integer primary key autoincrement,
				did text not null,
				rkey text,
				at_uri text generated always as ('at://' || did || '/' || 'sh.tangled.repo.issue.comment' || '/' || rkey) stored,

				-- at identifiers
				issue_at text not null,
				reply_to text, -- at_uri of parent comment

				-- content
				body text not null,
				created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),
				edited text,
				deleted text,

				-- constraints
				unique(did, rkey),
				unique(at_uri),
				foreign key (issue_at) references issues(at_uri) on delete cascade
			);
		`)
		if err != nil {
			return err
		}

		// transfer data
		_, err = tx.Exec(`
			insert into issue_comments (id, did, rkey, issue_at, body, created, edited, deleted)
			select
				c.id,
				c.owner_did,
				c.rkey,
				i.at_uri,  -- get at_uri from issues table
				c.body,
				c.created,
				c.edited,
				c.deleted
			from comments c
			join issues i on c.repo_at = i.repo_at and c.issue_id = i.issue_id;
		`)
		if err != nil {
			return err
		}

		// drop old table
		_, err = tx.Exec(`drop table comments`)
		return err
	})

	// add generated at_uri column to pulls table
	//
	// this requires a full table recreation because stored columns
	// cannot be added via alter
	//
	// disable foreign-keys for the next migration
	conn.ExecContext(ctx, "pragma foreign_keys = off;")
	orm.RunMigration(conn, logger, "add-at-uri-to-pulls", func(tx *sql.Tx) error {
		_, err := tx.Exec(`
		create table if not exists pulls_new (
			-- identifiers
			id integer primary key autoincrement,
			pull_id integer not null,
			at_uri text generated always as ('at://' || owner_did || '/' || 'sh.tangled.repo.pull' || '/' || rkey) stored,

			-- at identifiers
			repo_at text not null,
			owner_did text not null,
			rkey text not null,

			-- content
			title text not null,
			body text not null,
			target_branch text not null,
			state integer not null default 0 check (state in (0, 1, 2, 3)), -- closed, open, merged, deleted

			-- source info
			source_branch text,
			source_repo_at text,

			-- stacking
			stack_id text,
			change_id text,
			parent_change_id text,

			-- meta
			created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),

			-- constraints
			unique(repo_at, pull_id),
			unique(at_uri),
			foreign key (repo_at) references repos(at_uri) on delete cascade
		);
		`)
		if err != nil {
			return err
		}

		// transfer data
		_, err = tx.Exec(`
		insert into pulls_new (
			id, pull_id, repo_at, owner_did, rkey,
			title, body, target_branch, state,
			source_branch, source_repo_at,
			stack_id, change_id, parent_change_id,
			created
		)
		select
			id, pull_id, repo_at, owner_did, rkey,
			title, body, target_branch, state,
			source_branch, source_repo_at,
			stack_id, change_id, parent_change_id,
			created
			from pulls;
		`)
		if err != nil {
			return err
		}

		// drop old table
		_, err = tx.Exec(`drop table pulls`)
		if err != nil {
			return err
		}

		// rename new table
		_, err = tx.Exec(`alter table pulls_new rename to pulls`)
		return err
	})
	conn.ExecContext(ctx, "pragma foreign_keys = on;")

	// remove repo_at and pull_id from pull_submissions and replace with pull_at
	//
	// this requires a full table recreation because stored columns
	// cannot be added via alter
	//
	// disable foreign-keys for the next migration
	conn.ExecContext(ctx, "pragma foreign_keys = off;")
	orm.RunMigration(conn, logger, "remove-repo-at-pull-id-from-pull-submissions", func(tx *sql.Tx) error {
		_, err := tx.Exec(`
		create table if not exists pull_submissions_new (
			-- identifiers
			id integer primary key autoincrement,
			pull_at text not null,

			-- content, these are immutable, and require a resubmission to update
			round_number integer not null default 0,
			patch text,
			source_rev text,

			-- meta
			created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),

			-- constraints
			unique(pull_at, round_number),
			foreign key (pull_at) references pulls(at_uri) on delete cascade
		);
		`)
		if err != nil {
			return err
		}

		// transfer data, constructing pull_at from pulls table
		_, err = tx.Exec(`
		insert into pull_submissions_new (id, pull_at, round_number, patch, created)
		select
			ps.id,
			'at://' || p.owner_did || '/sh.tangled.repo.pull/' || p.rkey,
			ps.round_number,
			ps.patch,
			ps.created
		from pull_submissions ps
		join pulls p on ps.repo_at = p.repo_at and ps.pull_id = p.pull_id;
		`)
		if err != nil {
			return err
		}

		// drop old table
		_, err = tx.Exec(`drop table pull_submissions`)
		if err != nil {
			return err
		}

		// rename new table
		_, err = tx.Exec(`alter table pull_submissions_new rename to pull_submissions`)
		return err
	})
	conn.ExecContext(ctx, "pragma foreign_keys = on;")

	// knots may report the combined patch for a comparison, we can store that on the appview side
	// (but not on the pds record), because calculating the combined patch requires a git index
	orm.RunMigration(conn, logger, "add-combined-column-submissions", func(tx *sql.Tx) error {
		_, err := tx.Exec(`
			alter table pull_submissions add column combined text;
		`)
		return err
	})

	orm.RunMigration(conn, logger, "add-pronouns-profile", func(tx *sql.Tx) error {
		_, err := tx.Exec(`
			alter table profile add column pronouns text;
		`)
		return err
	})

	orm.RunMigration(conn, logger, "add-meta-column-repos", func(tx *sql.Tx) error {
		_, err := tx.Exec(`
			alter table repos add column website text;
			alter table repos add column topics text;
		`)
		return err
	})

	orm.RunMigration(conn, logger, "add-usermentioned-preference", func(tx *sql.Tx) error {
		_, err := tx.Exec(`
			alter table notification_preferences add column user_mentioned integer not null default 1;
		`)
		return err
	})

	// remove the foreign key constraints from stars.
	orm.RunMigration(conn, logger, "generalize-stars-subject", func(tx *sql.Tx) error {
		_, err := tx.Exec(`
			create table stars_new (
				id integer primary key autoincrement,
				did text not null,
				rkey text not null,

				subject_at text not null,

				created text not null default (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),
				unique(did, rkey),
				unique(did, subject_at)
			);

			insert into stars_new (
				id,
				did,
				rkey,
				subject_at,
				created
			)
			select
				id,
				starred_by_did,
				rkey,
				repo_at,
				created
			from stars;

			drop table stars;
			alter table stars_new rename to stars;

			create index if not exists idx_stars_created on stars(created);
			create index if not exists idx_stars_subject_at_created on stars(subject_at, created);
		`)
		return err
	})

	orm.RunMigration(conn, logger, "add-avatar-to-profile", func(tx *sql.Tx) error {
		_, err := tx.Exec(`
			alter table profile add column avatar text;
		`)
		return err
	})

	orm.RunMigration(conn, logger, "remove-profile-stats-column-constraint", func(tx *sql.Tx) error {
		_, err := tx.Exec(`
		-- create new table without the check constraint
		create table profile_stats_new (
			id integer primary key autoincrement,
			did text not null,
			kind text not null, -- no constraint this time
			foreign key (did) references profile(did) on delete cascade
		);

		-- copy data from old table
		insert into profile_stats_new (id, did, kind)
		select id, did, kind
		from profile_stats;

		-- drop old table
		drop table profile_stats;

		-- rename new table
		alter table profile_stats_new rename to profile_stats;
		`)
		return err
	})

	orm.RunMigration(conn, logger, "add-preferred-handle-profile", func(tx *sql.Tx) error {
		_, err := tx.Exec(`
			alter table profile add column preferred_handle text;
		`)
		return err
	})

	return &DB{
		db,
		logger,
	}, nil
}

func (d *DB) Close() error {
	return d.DB.Close()
}
