package postgresadmin

import (
	"context"
	"errors"

	"github.com/jackc/pgx/v5"

	"proxy-pool/internal/domain/adminstate"
)

func (adapter *Adapter) Snapshot(ctx context.Context) (adminstate.Snapshot, error) {
	if err := contextError(ctx); err != nil {
		return adminstate.Snapshot{}, err
	}
	if !adapter.valid() {
		return adminstate.Snapshot{}, adminstate.ErrInvalidCommand
	}
	tx, err := adapter.begin(ctx, pgx.TxOptions{
		IsoLevel:   pgx.RepeatableRead,
		AccessMode: pgx.ReadOnly,
	}, "begin snapshot")
	if err != nil {
		return adminstate.Snapshot{}, err
	}
	defer rollback(tx)

	snapshot := adminstate.Snapshot{}
	var revision int64
	if err := tx.QueryRow(ctx, currentRevisionSQL).Scan(&revision); err != nil {
		return adminstate.Snapshot{}, databaseError(ctx, "read snapshot revision", err)
	}
	convertedRevision, ok := domainID(revision)
	if !ok {
		return adminstate.Snapshot{}, unavailable("decode snapshot revision")
	}
	snapshot.Revision = convertedRevision

	var configRevision int64
	config := adminstate.ConfigRevision{}
	err = tx.QueryRow(ctx, `
		SELECT revision, config_version, checksum::text, source, created_at
		FROM config_revisions
		ORDER BY revision DESC
		LIMIT 1`).Scan(
		&configRevision,
		&config.ConfigVersion,
		&config.Checksum,
		&config.Source,
		&config.CreatedAt,
	)
	switch {
	case err == nil:
		converted, ok := domainID(configRevision)
		if !ok {
			return adminstate.Snapshot{}, unavailable("decode config revision")
		}
		config.Revision = converted
		config.CreatedAt = utc(config.CreatedAt)
		snapshot.Config = &config
	case !errors.Is(err, pgx.ErrNoRows):
		return adminstate.Snapshot{}, databaseError(ctx, "read config snapshot", err)
	}

	upstreams, err := readUpstreamSnapshot(ctx, tx)
	if err != nil {
		return adminstate.Snapshot{}, err
	}
	snapshot.Upstreams = upstreams
	routings, err := readRoutingSnapshot(ctx, tx)
	if err != nil {
		return adminstate.Snapshot{}, err
	}
	snapshot.Routings = routings
	if err := commit(ctx, tx, "commit snapshot"); err != nil {
		return adminstate.Snapshot{}, err
	}
	return snapshot, nil
}

func (adapter *Adapter) ReadAudit(
	ctx context.Context,
	query adminstate.AuditQuery,
) ([]adminstate.AuditRecord, error) {
	if err := contextError(ctx); err != nil {
		return nil, err
	}
	if query.Validate() != nil || !adapter.valid() {
		return nil, adminstate.ErrInvalidCommand
	}
	afterID, ok := databaseID(query.AfterID)
	if !ok {
		return []adminstate.AuditRecord{}, nil
	}
	tx, err := adapter.begin(ctx, pgx.TxOptions{AccessMode: pgx.ReadOnly}, "begin audit read")
	if err != nil {
		return nil, err
	}
	defer rollback(tx)

	rows, err := tx.Query(ctx, `
		SELECT id, request_id, actor_id, COALESCE(host(source_ip), ''), action,
			resource_type, resource_name, changed, revision, reason, occurred_at
		FROM admin_audit_log
		WHERE id > $1
		ORDER BY id
		LIMIT $2`, afterID, query.Limit)
	if err != nil {
		return nil, databaseError(ctx, "read audit page", err)
	}
	defer rows.Close()

	records := make([]adminstate.AuditRecord, 0, query.Limit)
	for rows.Next() {
		record := adminstate.AuditRecord{}
		var id int64
		var revision int64
		var action string
		if err := rows.Scan(
			&id,
			&record.RequestID,
			&record.Actor.ID,
			&record.Actor.SourceIP,
			&action,
			&record.ResourceType,
			&record.ResourceName,
			&record.Changed,
			&revision,
			&record.Reason,
			&record.OccurredAt,
		); err != nil {
			return nil, databaseError(ctx, "decode audit page", err)
		}
		convertedID, idOK := domainID(id)
		convertedRevision, revisionOK := domainID(revision)
		if !idOK || !revisionOK {
			return nil, unavailable("decode audit page")
		}
		record.ID = convertedID
		record.Revision = convertedRevision
		record.Action = adminstate.Action(action)
		record.OccurredAt = utc(record.OccurredAt)
		records = append(records, record)
	}
	if err := rows.Err(); err != nil {
		return nil, databaseError(ctx, "read audit page", err)
	}
	if err := commit(ctx, tx, "commit audit read"); err != nil {
		return nil, err
	}
	return records, nil
}

func readUpstreamSnapshot(ctx context.Context, tx pgx.Tx) ([]adminstate.UpstreamState, error) {
	rows, err := tx.Query(ctx, `
		SELECT name, enabled, revision, updated_at
		FROM upstream_admin_state
		ORDER BY name`)
	if err != nil {
		return nil, databaseError(ctx, "read upstream snapshot", err)
	}
	defer rows.Close()

	states := make([]adminstate.UpstreamState, 0)
	for rows.Next() {
		state := adminstate.UpstreamState{}
		var revision int64
		if err := rows.Scan(&state.Name, &state.Enabled, &revision, &state.UpdatedAt); err != nil {
			return nil, databaseError(ctx, "decode upstream snapshot", err)
		}
		converted, ok := domainID(revision)
		if !ok {
			return nil, unavailable("decode upstream snapshot")
		}
		state.Revision = converted
		state.UpdatedAt = utc(state.UpdatedAt)
		states = append(states, state)
	}
	if err := rows.Err(); err != nil {
		return nil, databaseError(ctx, "read upstream snapshot", err)
	}
	return states, nil
}

func readRoutingSnapshot(ctx context.Context, tx pgx.Tx) ([]adminstate.RoutingState, error) {
	rows, err := tx.Query(ctx, `
		SELECT name, enabled, upstreams, current_upstream, revision, updated_at
		FROM routing_admin_state
		ORDER BY name`)
	if err != nil {
		return nil, databaseError(ctx, "read routing snapshot", err)
	}
	defer rows.Close()

	states := make([]adminstate.RoutingState, 0)
	for rows.Next() {
		state := adminstate.RoutingState{}
		var revision int64
		if err := rows.Scan(
			&state.Name,
			&state.Enabled,
			&state.Upstreams,
			&state.CurrentUpstream,
			&revision,
			&state.UpdatedAt,
		); err != nil {
			return nil, databaseError(ctx, "decode routing snapshot", err)
		}
		converted, ok := domainID(revision)
		if !ok {
			return nil, unavailable("decode routing snapshot")
		}
		state.Revision = converted
		state.UpdatedAt = utc(state.UpdatedAt)
		state.Upstreams = append([]string(nil), state.Upstreams...)
		states = append(states, state)
	}
	if err := rows.Err(); err != nil {
		return nil, databaseError(ctx, "read routing snapshot", err)
	}
	return states, nil
}