package store

import (
	"context"
	"database/sql"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"strconv"
	"time"

	"github.com/cosmic-clash/cosmic-clash/server/domain"
)

// DurableAssignment is the persistence form of a verified assignment-ready
// projection. It deliberately keeps player ownership in the primary key and
// query predicate so another participant cannot recover its join material.
type DurableAssignment struct {
	MatchID           string
	PlayerID          string
	AllocationID      string
	ServerID          string
	Slot              int
	Region            string
	ClientBuild       string
	ProtocolVersion   int
	Transport         string
	Endpoint          string
	JoinAuthorisation string
	ManifestDigest    []byte
	ExpiresAt         time.Time
	Revision          uint64
}

type PostgresRosterStore struct{ DB *sql.DB }

func (s PostgresRosterStore) PublishRoster(ctx context.Context, assignment domain.Assignment, roster []domain.SignedJoinAuthorisation, verify func([]byte, []byte) bool) error {
	return SaveVerifiedAssignmentRoster(ctx, s.DB, assignment, roster, verify)
}

const AssignmentUpsertSQL = `INSERT INTO assignments
    (match_id, player_id, allocation_id, server_id, slot, region, client_build,
     protocol_version, transport, endpoint, join_authorisation, manifest_digest,
     expires_at, revision)
VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14)
ON CONFLICT (match_id, player_id) DO UPDATE SET
    allocation_id = EXCLUDED.allocation_id, server_id = EXCLUDED.server_id,
    slot = EXCLUDED.slot, region = EXCLUDED.region, client_build = EXCLUDED.client_build,
    protocol_version = EXCLUDED.protocol_version, transport = EXCLUDED.transport,
    endpoint = EXCLUDED.endpoint, join_authorisation = EXCLUDED.join_authorisation,
    manifest_digest = EXCLUDED.manifest_digest, expires_at = EXCLUDED.expires_at,
    revision = EXCLUDED.revision
WHERE assignments.allocation_id = EXCLUDED.allocation_id
  AND assignments.server_id = EXCLUDED.server_id
  AND assignments.slot = EXCLUDED.slot
  AND assignments.region = EXCLUDED.region
  AND assignments.client_build = EXCLUDED.client_build
  AND assignments.protocol_version = EXCLUDED.protocol_version
  AND assignments.transport = EXCLUDED.transport
  AND assignments.endpoint = EXCLUDED.endpoint
  AND assignments.join_authorisation = EXCLUDED.join_authorisation
  AND assignments.manifest_digest = EXCLUDED.manifest_digest
  AND assignments.expires_at = EXCLUDED.expires_at
  AND assignments.revision = EXCLUDED.revision`

const AssignmentSelectSQL = `SELECT match_id, player_id, allocation_id, server_id,
    slot, region, client_build, protocol_version, transport, endpoint,
    join_authorisation, manifest_digest, expires_at, revision
FROM assignments
WHERE match_id = $1 AND player_id = $2 AND expires_at > $3`

func validateDurableAssignment(assignment DurableAssignment) error {
	if assignment.MatchID == "" || assignment.PlayerID == "" || assignment.AllocationID == "" || assignment.ServerID == "" || assignment.Slot < 0 || assignment.Slot > 5 || (assignment.Region != "EU" && assignment.Region != "NA") || assignment.ClientBuild == "" || assignment.ProtocolVersion < 1 || (assignment.Transport != "enet" && assignment.Transport != "steam_sdr") || assignment.Endpoint == "" || assignment.JoinAuthorisation == "" || len(assignment.ManifestDigest) == 0 || assignment.ExpiresAt.IsZero() || assignment.Revision < 0 {
		return fmt.Errorf("invalid durable assignment")
	}
	return nil
}

func SaveAssignment(ctx context.Context, db *sql.DB, assignment DurableAssignment) error {
	if db == nil {
		return fmt.Errorf("invalid assignment database")
	}
	if err := validateDurableAssignment(assignment); err != nil {
		return err
	}
	result, err := db.ExecContext(ctx, AssignmentUpsertSQL, assignment.MatchID, assignment.PlayerID, assignment.AllocationID, assignment.ServerID, assignment.Slot, assignment.Region, assignment.ClientBuild, assignment.ProtocolVersion, assignment.Transport, assignment.Endpoint, assignment.JoinAuthorisation, assignment.ManifestDigest, assignment.ExpiresAt, assignment.Revision)
	if err != nil {
		return err
	}
	changed, err := result.RowsAffected()
	if err != nil {
		return err
	}
	if changed != 1 {
		return fmt.Errorf("assignment persistence conflict")
	}
	return nil
}

// SaveAssignments publishes a complete signed roster atomically. Assignment
// readiness is a match boundary: exposing only some players would let the
// control plane tell different participants incompatible stories after a
// transient database failure.
func SaveAssignments(ctx context.Context, db *sql.DB, assignments []DurableAssignment) error {
	if db == nil || len(assignments) == 0 {
		return fmt.Errorf("invalid assignment batch")
	}
	tx, err := db.BeginTx(ctx, nil)
	if err != nil {
		return err
	}
	defer tx.Rollback()
	seen := make(map[string]struct{}, len(assignments))
	for _, assignment := range assignments {
		if err := validateDurableAssignment(assignment); err != nil {
			return err
		}
		key := assignment.MatchID + "\x00" + assignment.PlayerID
		if _, ok := seen[key]; ok {
			return fmt.Errorf("duplicate assignment in batch")
		}
		seen[key] = struct{}{}
		result, err := tx.ExecContext(ctx, AssignmentUpsertSQL, assignment.MatchID, assignment.PlayerID, assignment.AllocationID, assignment.ServerID, assignment.Slot, assignment.Region, assignment.ClientBuild, assignment.ProtocolVersion, assignment.Transport, assignment.Endpoint, assignment.JoinAuthorisation, assignment.ManifestDigest, assignment.ExpiresAt, assignment.Revision)
		if err != nil {
			return err
		}
		changed, err := result.RowsAffected()
		if err != nil {
			return err
		}
		if changed != 1 {
			return fmt.Errorf("assignment persistence conflict")
		}
	}
	return tx.Commit()
}

// SaveVerifiedAssignmentRoster converts the backend-verified signed roster to
// player-scoped rows. It rechecks the claims at this persistence boundary so a
// caller cannot accidentally publish a token for another match or slot.
func SaveVerifiedAssignmentRoster(ctx context.Context, db *sql.DB, assignment domain.Assignment, roster []domain.SignedJoinAuthorisation, verify func([]byte, []byte) bool) error {
	if assignment.Allocation.State != domain.ServerAllocated || len(roster) == 0 || verify == nil {
		return fmt.Errorf("invalid verified assignment roster")
	}
	digest := domain.ManifestDigest(assignment.Manifest)
	rows := make([]DurableAssignment, 0, len(roster))
	for _, signed := range roster {
		auth := signed.Authorisation
		if err := validateSignedRosterEntry(assignment, signed, verify); err != nil {
			return err
		}
		envelope, err := json.Marshal(signed)
		if err != nil {
			return fmt.Errorf("encode signed assignment roster: %w", err)
		}
		rows = append(rows, DurableAssignment{
			MatchID: assignment.Allocation.MatchID, PlayerID: auth.PlayerID,
			AllocationID: assignment.Allocation.AllocationID, ServerID: assignment.Allocation.ServerID,
			Slot: auth.Slot, Region: assignment.Allocation.Region, ClientBuild: assignment.Allocation.Build,
			ProtocolVersion: assignment.Allocation.Protocol, Transport: assignment.Allocation.Transport,
			Endpoint: assignment.Endpoint, JoinAuthorisation: base64.RawURLEncoding.EncodeToString(envelope),
			ManifestDigest: digest[:], ExpiresAt: auth.ExpiresAt, Revision: 1,
		})
	}
	return SaveAssignments(ctx, db, rows)
}

func validateSignedRosterEntry(assignment domain.Assignment, signed domain.SignedJoinAuthorisation, verify func([]byte, []byte) bool) error {
	auth := signed.Authorisation
	if len(signed.Signature) == 0 || verify == nil || !verify(domain.JoinAuthorisationBytes(auth), signed.Signature) || auth.MatchID != assignment.Allocation.MatchID || auth.ServerID != assignment.Allocation.ServerID || auth.Protocol != strconv.Itoa(assignment.Allocation.Protocol) || auth.PlayerID == "" || auth.Slot < 0 || auth.Slot > 5 || auth.ExpiresAt.IsZero() {
		return fmt.Errorf("invalid signed assignment roster")
	}
	return nil
}

func GetAssignment(ctx context.Context, db *sql.DB, playerID, matchID string, now time.Time) (DurableAssignment, error) {
	if db == nil || playerID == "" || matchID == "" || now.IsZero() {
		return DurableAssignment{}, fmt.Errorf("invalid assignment recovery arguments")
	}
	var assignment DurableAssignment
	err := db.QueryRowContext(ctx, AssignmentSelectSQL, matchID, playerID, now).Scan(&assignment.MatchID, &assignment.PlayerID, &assignment.AllocationID, &assignment.ServerID, &assignment.Slot, &assignment.Region, &assignment.ClientBuild, &assignment.ProtocolVersion, &assignment.Transport, &assignment.Endpoint, &assignment.JoinAuthorisation, &assignment.ManifestDigest, &assignment.ExpiresAt, &assignment.Revision)
	if err != nil {
		return DurableAssignment{}, err
	}
	if err := validateDurableAssignment(assignment); err != nil {
		return DurableAssignment{}, err
	}
	return assignment, nil
}