package spool

import (
	"context"
	"crypto/sha256"
	"database/sql"
	"encoding/hex"
	"fmt"
)

type migration struct {
	version uint32
	sql     string
}

var migrations = []migration{{version: 1, sql: schemaV1}}

func applyMigrations(ctx context.Context, db *sql.DB) error {
	if _, err := db.ExecContext(ctx, `CREATE TABLE IF NOT EXISTS schema_migrations (
version INTEGER PRIMARY KEY CHECK(version > 0), checksum TEXT NOT NULL, applied_at INTEGER NOT NULL
) STRICT`); err != nil {
		return fmt.Errorf("create client spool migration table: %w", err)
	}
	for _, current := range migrations {
		checksumBytes := sha256.Sum256([]byte(current.sql))
		checksum := hex.EncodeToString(checksumBytes[:])
		var stored string
		err := db.QueryRowContext(ctx, `SELECT checksum FROM schema_migrations WHERE version = ?`, current.version).Scan(&stored)
		if err == nil {
			if stored != checksum {
				return fmt.Errorf("client spool migration %d checksum mismatch", current.version)
			}
			continue
		}
		if err != sql.ErrNoRows {
			return err
		}
		tx, err := db.BeginTx(ctx, nil)
		if err != nil {
			return err
		}
		if _, err = tx.ExecContext(ctx, current.sql); err == nil {
			_, err = tx.ExecContext(ctx, `INSERT INTO schema_migrations(version, checksum, applied_at) VALUES (?, ?, unixepoch())`, current.version, checksum)
		}
		if err != nil {
			_ = tx.Rollback()
			return fmt.Errorf("apply client spool migration %d: %w", current.version, err)
		}
		if err := tx.Commit(); err != nil {
			return fmt.Errorf("commit client spool migration %d: %w", current.version, err)
		}
	}
	return nil
}

const schemaV1 = `
CREATE TABLE commands (
  issue_uuid BLOB PRIMARY KEY CHECK(length(issue_uuid) = 16),
  immutable_sha256 BLOB NOT NULL CHECK(length(immutable_sha256) = 32),
  command_revision INTEGER NOT NULL CHECK(command_revision > 0),
  phase INTEGER NOT NULL CHECK(phase BETWEEN 1 AND 11),
  terminal INTEGER NOT NULL DEFAULT 0 CHECK(terminal IN (0, 1)),
  next_local_ordinal INTEGER NOT NULL DEFAULT 1 CHECK(next_local_ordinal > 0),
  next_event_seq INTEGER NOT NULL DEFAULT 1 CHECK(next_event_seq > 0),
  last_server_ack INTEGER NOT NULL DEFAULT 0 CHECK(last_server_ack >= 0),
  accepted_at INTEGER NOT NULL
) STRICT;
CREATE TABLE events (
  issue_uuid BLOB NOT NULL REFERENCES commands(issue_uuid) ON DELETE CASCADE,
  local_ordinal INTEGER NOT NULL CHECK(local_ordinal > 0),
  event_seq INTEGER CHECK(event_seq IS NULL OR event_seq > 0),
  event_kind INTEGER NOT NULL CHECK(event_kind > 0),
  compression INTEGER NOT NULL CHECK(compression IN (1, 2)),
  raw_bytes INTEGER NOT NULL CHECK(raw_bytes >= 0),
  payload BLOB NOT NULL,
  payload_sha256 BLOB NOT NULL CHECK(length(payload_sha256) = 32),
  created_at INTEGER NOT NULL,
  PRIMARY KEY(issue_uuid, local_ordinal),
  UNIQUE(issue_uuid, event_seq)
) STRICT, WITHOUT ROWID;
CREATE INDEX events_send_window ON events(issue_uuid, event_seq, local_ordinal);
CREATE TABLE command_tombstones (
  issue_uuid BLOB PRIMARY KEY CHECK(length(issue_uuid) = 16),
  immutable_sha256 BLOB NOT NULL CHECK(length(immutable_sha256) = 32),
  acknowledged_at INTEGER NOT NULL
) STRICT;
CREATE INDEX tombstones_fifo ON command_tombstones(acknowledged_at, issue_uuid);
`