// Package storage defines the interface for issue storage backends.
package storage

import (
	"context"
	"database/sql"

	"github.com/steveyegge/beads/internal/types"
)

// Transaction provides atomic multi-operation support within a single database transaction.
//
// The Transaction interface exposes a subset of Storage methods that execute within
// a single database transaction. This enables atomic workflows where multiple operations
// must either all succeed or all fail (e.g., creating issues with dependencies and labels).
//
// # Transaction Semantics
//
//   - All operations within the transaction share the same database connection
//   - Changes are not visible to other connections until commit
//   - If any operation returns an error, the transaction is rolled back
//   - If the callback function panics, the transaction is rolled back
//   - On successful return from the callback, the transaction is committed
//
// # SQLite Specifics
//
//   - Uses BEGIN IMMEDIATE mode to acquire write lock early
//   - This prevents deadlocks when multiple operations compete for the same lock
//   - IMMEDIATE mode serializes concurrent transactions properly
//
// # Example Usage
//
//	err := store.RunInTransaction(ctx, func(tx storage.Transaction) error {
//	    // Create parent issue
//	    if err := tx.CreateIssue(ctx, parentIssue, actor); err != nil {
//	        return err // Triggers rollback
//	    }
//	    // Create child issue
//	    if err := tx.CreateIssue(ctx, childIssue, actor); err != nil {
//	        return err // Triggers rollback
//	    }
//	    // Add dependency between them
//	    if err := tx.AddDependency(ctx, dep, actor); err != nil {
//	        return err // Triggers rollback
//	    }
//	    return nil // Triggers commit
//	})
type Transaction interface {
	// Issue operations
	CreateIssue(ctx context.Context, issue *types.Issue, actor string) error
	CreateIssues(ctx context.Context, issues []*types.Issue, actor string) error
	UpdateIssue(ctx context.Context, id string, updates map[string]interface{}, actor string) error
	CloseIssue(ctx context.Context, id string, reason string, actor string, session string) error
	DeleteIssue(ctx context.Context, id string) error
	GetIssue(ctx context.Context, id string) (*types.Issue, error)                                  // For read-your-writes within transaction
	SearchIssues(ctx context.Context, query string, filter types.IssueFilter) ([]*types.Issue, error) // For read-your-writes within transaction

	// Dependency operations
	AddDependency(ctx context.Context, dep *types.Dependency, actor string) error
	RemoveDependency(ctx context.Context, issueID, dependsOnID string, actor string) error

	// Label operations
	AddLabel(ctx context.Context, issueID, label, actor string) error
	RemoveLabel(ctx context.Context, issueID, label, actor string) error

	// Config operations (for atomic config + issue workflows)
	SetConfig(ctx context.Context, key, value string) error
	GetConfig(ctx context.Context, key string) (string, error)

	// Metadata operations (for internal state like import hashes)
	SetMetadata(ctx context.Context, key, value string) error
	GetMetadata(ctx context.Context, key string) (string, error)

	// Comment operations
	AddComment(ctx context.Context, issueID, actor, comment string) error
}

// Storage defines the interface for issue storage backends
type Storage interface {
	// Issues
	CreateIssue(ctx context.Context, issue *types.Issue, actor string) error
	CreateIssues(ctx context.Context, issues []*types.Issue, actor string) error
	GetIssue(ctx context.Context, id string) (*types.Issue, error)
	GetIssueByExternalRef(ctx context.Context, externalRef string) (*types.Issue, error)
	UpdateIssue(ctx context.Context, id string, updates map[string]interface{}, actor string) error
	CloseIssue(ctx context.Context, id string, reason string, actor string, session string) error
	DeleteIssue(ctx context.Context, id string) error
	SearchIssues(ctx context.Context, query string, filter types.IssueFilter) ([]*types.Issue, error)

	// Dependencies
	AddDependency(ctx context.Context, dep *types.Dependency, actor string) error
	RemoveDependency(ctx context.Context, issueID, dependsOnID string, actor string) error
	GetDependencies(ctx context.Context, issueID string) ([]*types.Issue, error)
	GetDependents(ctx context.Context, issueID string) ([]*types.Issue, error)
	GetDependenciesWithMetadata(ctx context.Context, issueID string) ([]*types.IssueWithDependencyMetadata, error)
	GetDependentsWithMetadata(ctx context.Context, issueID string) ([]*types.IssueWithDependencyMetadata, error)
	GetDependencyRecords(ctx context.Context, issueID string) ([]*types.Dependency, error)
	GetAllDependencyRecords(ctx context.Context) (map[string][]*types.Dependency, error)
	GetDependencyCounts(ctx context.Context, issueIDs []string) (map[string]*types.DependencyCounts, error)
	GetDependencyTree(ctx context.Context, issueID string, maxDepth int, showAllPaths bool, reverse bool) ([]*types.TreeNode, error)
	DetectCycles(ctx context.Context) ([][]*types.Issue, error)

	// Labels
	AddLabel(ctx context.Context, issueID, label, actor string) error
	RemoveLabel(ctx context.Context, issueID, label, actor string) error
	GetLabels(ctx context.Context, issueID string) ([]string, error)
	GetLabelsForIssues(ctx context.Context, issueIDs []string) (map[string][]string, error)
	GetIssuesByLabel(ctx context.Context, label string) ([]*types.Issue, error)

	// Ready Work & Blocking
	GetReadyWork(ctx context.Context, filter types.WorkFilter) ([]*types.Issue, error)
	GetBlockedIssues(ctx context.Context, filter types.WorkFilter) ([]*types.BlockedIssue, error)
	IsBlocked(ctx context.Context, issueID string) (bool, []string, error) // GH#962: Check if issue has open blockers
	GetEpicsEligibleForClosure(ctx context.Context) ([]*types.EpicStatus, error)
	GetStaleIssues(ctx context.Context, filter types.StaleFilter) ([]*types.Issue, error)
	GetNewlyUnblockedByClose(ctx context.Context, closedIssueID string) ([]*types.Issue, error) // GH#679

	// Events
	AddComment(ctx context.Context, issueID, actor, comment string) error
	GetEvents(ctx context.Context, issueID string, limit int) ([]*types.Event, error)

	// Comments
	AddIssueComment(ctx context.Context, issueID, author, text string) (*types.Comment, error)
	GetIssueComments(ctx context.Context, issueID string) ([]*types.Comment, error)
	GetCommentsForIssues(ctx context.Context, issueIDs []string) (map[string][]*types.Comment, error)

	// Statistics
	GetStatistics(ctx context.Context) (*types.Statistics, error)

	// Molecule progress (efficient for large molecules)
	GetMoleculeProgress(ctx context.Context, moleculeID string) (*types.MoleculeProgressStats, error)

	// Dirty tracking (for incremental JSONL export)
	GetDirtyIssues(ctx context.Context) ([]string, error)
	GetDirtyIssueHash(ctx context.Context, issueID string) (string, error) // For timestamp-only dedup (bd-164)
	ClearDirtyIssuesByID(ctx context.Context, issueIDs []string) error

	// Export hash tracking (for timestamp-only dedup, bd-164)
	GetExportHash(ctx context.Context, issueID string) (string, error)
	SetExportHash(ctx context.Context, issueID, contentHash string) error
	ClearAllExportHashes(ctx context.Context) error
	
	// JSONL file integrity (bd-160)
	GetJSONLFileHash(ctx context.Context) (string, error)
	SetJSONLFileHash(ctx context.Context, fileHash string) error

	// ID Generation
	GetNextChildID(ctx context.Context, parentID string) (string, error)

	// Config
	SetConfig(ctx context.Context, key, value string) error
	GetConfig(ctx context.Context, key string) (string, error)
	GetAllConfig(ctx context.Context) (map[string]string, error)
	DeleteConfig(ctx context.Context, key string) error
	GetCustomStatuses(ctx context.Context) ([]string, error) // Custom status states from status.custom config
	GetCustomTypes(ctx context.Context) ([]string, error)    // Custom issue types from types.custom config

	// Metadata (for internal state like import hashes)
	SetMetadata(ctx context.Context, key, value string) error
	GetMetadata(ctx context.Context, key string) (string, error)

	// Prefix rename operations
	UpdateIssueID(ctx context.Context, oldID, newID string, issue *types.Issue, actor string) error
	RenameDependencyPrefix(ctx context.Context, oldPrefix, newPrefix string) error
	RenameCounterPrefix(ctx context.Context, oldPrefix, newPrefix string) error

	// Transactions
	//
	// RunInTransaction executes a function within a database transaction.
	// The Transaction interface provides atomic multi-operation support.
	//
	// Transaction behavior:
	//   - If fn returns nil, the transaction is committed
	//   - If fn returns an error, the transaction is rolled back
	//   - If fn panics, the transaction is rolled back and the panic is re-raised
	//   - Uses BEGIN IMMEDIATE for SQLite to acquire write lock early
	//
	// Example:
	//   err := store.RunInTransaction(ctx, func(tx storage.Transaction) error {
	//       if err := tx.CreateIssue(ctx, issue, actor); err != nil {
	//           return err // Triggers rollback
	//       }
	//       return nil // Triggers commit
	//   })
	RunInTransaction(ctx context.Context, fn func(tx Transaction) error) error

	// Lifecycle
	Close() error

	// Database path (for daemon validation)
	Path() string

	// UnderlyingDB returns the underlying *sql.DB connection
	// This is provided for extensions (like VC) that need to create their own tables
	// in the same database. Extensions should use foreign keys to reference core tables.
	// WARNING: Direct database access bypasses the storage layer. Use with caution.
	UnderlyingDB() *sql.DB

	// UnderlyingConn returns a single connection from the pool for scoped use.
	// Useful for migrations and DDL operations that benefit from explicit connection lifetime.
	// The caller MUST close the connection when done to return it to the pool.
	// For general queries, prefer UnderlyingDB() which manages the pool automatically.
	UnderlyingConn(ctx context.Context) (*sql.Conn, error)
}

// Config holds database configuration
type Config struct {
	Backend string // "sqlite" or "postgres"

	// SQLite config
	Path string // database file path

	// PostgreSQL config
	Host     string
	Port     int
	Database string
	User     string
	Password string
	SSLMode  string
}