package main

import (
	"context"
	"fmt"
	"os"
	"regexp"
	"strconv"
	"strings"
	"time"

	"github.com/spf13/cobra"
	"github.com/steveyegge/beads/internal/debug"
	"github.com/steveyegge/beads/internal/linear"
	"github.com/steveyegge/beads/internal/storage/sqlite"
	"github.com/steveyegge/beads/internal/types"
)

// linearCmd is the root command for Linear integration.
var linearCmd = &cobra.Command{
	Use:     "linear",
	GroupID: "advanced",
	Short:   "Linear integration commands",
	Long: `Synchronize issues between beads and Linear.

Configuration:
  bd config set linear.api_key "YOUR_API_KEY"
  bd config set linear.team_id "TEAM_ID"
  bd config set linear.project_id "PROJECT_ID"  # Optional: sync only this project

Environment variables (alternative to config):
  LINEAR_API_KEY - Linear API key
  LINEAR_TEAM_ID - Linear team ID (UUID)

Data Mapping (optional, sensible defaults provided):
  Priority mapping (Linear 0-4 to Beads 0-4):
    bd config set linear.priority_map.0 4    # No priority -> Backlog
    bd config set linear.priority_map.1 0    # Urgent -> Critical
    bd config set linear.priority_map.2 1    # High -> High
    bd config set linear.priority_map.3 2    # Medium -> Medium
    bd config set linear.priority_map.4 3    # Low -> Low

  State mapping (Linear state type to Beads status):
    bd config set linear.state_map.backlog open
    bd config set linear.state_map.unstarted open
    bd config set linear.state_map.started in_progress
    bd config set linear.state_map.completed closed
    bd config set linear.state_map.canceled closed
    bd config set linear.state_map.my_custom_state in_progress  # Custom state names

  Label to issue type mapping:
    bd config set linear.label_type_map.bug bug
    bd config set linear.label_type_map.feature feature
    bd config set linear.label_type_map.epic epic

  Relation type mapping (Linear relations to Beads dependencies):
    bd config set linear.relation_map.blocks blocks
    bd config set linear.relation_map.blockedBy blocks
    bd config set linear.relation_map.duplicate duplicates
    bd config set linear.relation_map.related related

  ID generation (optional, hash IDs to match bd/Jira hash mode):
    bd config set linear.id_mode "hash"      # hash (default)
    bd config set linear.hash_length "6"     # hash length 3-8 (default: 6)

Examples:
  bd linear sync --pull         # Import issues from Linear
  bd linear sync --push         # Export issues to Linear
  bd linear sync                # Bidirectional sync (pull then push)
  bd linear sync --dry-run      # Preview sync without changes
  bd linear status              # Show sync status`,
}

// linearSyncCmd handles synchronization with Linear.
var linearSyncCmd = &cobra.Command{
	Use:   "sync",
	Short: "Synchronize issues with Linear",
	Long: `Synchronize issues between beads and Linear.

Modes:
  --pull         Import issues from Linear into beads
  --push         Export issues from beads to Linear
  (no flags)     Bidirectional sync: pull then push, with conflict resolution

Conflict Resolution:
  By default, newer timestamp wins. Override with:
  --prefer-local    Always prefer local beads version
  --prefer-linear   Always prefer Linear version

Examples:
  bd linear sync --pull                # Import from Linear
  bd linear sync --push --create-only  # Push new issues only
  bd linear sync --dry-run             # Preview without changes
  bd linear sync --prefer-local        # Bidirectional, local wins`,
	Run: runLinearSync,
}

// linearStatusCmd shows the current sync status.
var linearStatusCmd = &cobra.Command{
	Use:   "status",
	Short: "Show Linear sync status",
	Long: `Show the current Linear sync status, including:
  - Last sync timestamp
  - Configuration status
  - Number of issues with Linear links
  - Issues pending push (no external_ref)`,
	Run: runLinearStatus,
}

// linearTeamsCmd lists available teams.
var linearTeamsCmd = &cobra.Command{
	Use:   "teams",
	Short: "List available Linear teams",
	Long: `List all teams accessible with your Linear API key.

Use this to find the team ID (UUID) needed for configuration.

Example:
  bd linear teams
  bd config set linear.team_id "12345678-1234-1234-1234-123456789abc"`,
	Run: runLinearTeams,
}

func init() {
	linearSyncCmd.Flags().Bool("pull", false, "Pull issues from Linear")
	linearSyncCmd.Flags().Bool("push", false, "Push issues to Linear")
	linearSyncCmd.Flags().Bool("dry-run", false, "Preview sync without making changes")
	linearSyncCmd.Flags().Bool("prefer-local", false, "Prefer local version on conflicts")
	linearSyncCmd.Flags().Bool("prefer-linear", false, "Prefer Linear version on conflicts")
	linearSyncCmd.Flags().Bool("create-only", false, "Only create new issues, don't update existing")
	linearSyncCmd.Flags().Bool("update-refs", true, "Update external_ref after creating Linear issues")
	linearSyncCmd.Flags().String("state", "all", "Issue state to sync: open, closed, all")

	linearCmd.AddCommand(linearSyncCmd)
	linearCmd.AddCommand(linearStatusCmd)
	linearCmd.AddCommand(linearTeamsCmd)
	rootCmd.AddCommand(linearCmd)
}

func runLinearSync(cmd *cobra.Command, args []string) {
	pull, _ := cmd.Flags().GetBool("pull")
	push, _ := cmd.Flags().GetBool("push")
	dryRun, _ := cmd.Flags().GetBool("dry-run")
	preferLocal, _ := cmd.Flags().GetBool("prefer-local")
	preferLinear, _ := cmd.Flags().GetBool("prefer-linear")
	createOnly, _ := cmd.Flags().GetBool("create-only")
	updateRefs, _ := cmd.Flags().GetBool("update-refs")
	state, _ := cmd.Flags().GetString("state")

	if !dryRun {
		CheckReadonly("linear sync")
	}

	if preferLocal && preferLinear {
		fmt.Fprintf(os.Stderr, "Error: cannot use both --prefer-local and --prefer-linear\n")
		os.Exit(1)
	}

	if err := ensureStoreActive(); err != nil {
		fmt.Fprintf(os.Stderr, "Error: database not available: %v\n", err)
		os.Exit(1)
	}

	if err := validateLinearConfig(); err != nil {
		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
		os.Exit(1)
	}

	if !pull && !push {
		pull = true
		push = true
	}

	ctx := rootCtx
	result := &linear.SyncResult{Success: true}
	var forceUpdateIDs map[string]bool
	var skipUpdateIDs map[string]bool
	var prePullConflicts []linear.Conflict
	var prePullSkipLinearIDs map[string]bool

	if pull {
		if preferLocal || preferLinear {
			conflicts, err := detectLinearConflicts(ctx)
			if err != nil {
				result.Warnings = append(result.Warnings, fmt.Sprintf("conflict detection failed: %v", err))
			} else if len(conflicts) > 0 {
				prePullConflicts = conflicts
				if preferLocal {
					prePullSkipLinearIDs = make(map[string]bool, len(conflicts))
					forceUpdateIDs = make(map[string]bool, len(conflicts))
					for _, conflict := range conflicts {
						prePullSkipLinearIDs[conflict.LinearIdentifier] = true
						forceUpdateIDs[conflict.IssueID] = true
					}
				} else if preferLinear {
					skipUpdateIDs = make(map[string]bool, len(conflicts))
					for _, conflict := range conflicts {
						skipUpdateIDs[conflict.IssueID] = true
					}
				}
			}
		}

		if dryRun {
			fmt.Println("→ [DRY RUN] Would pull issues from Linear")
		} else {
			fmt.Println("→ Pulling issues from Linear...")
		}

		pullStats, err := doPullFromLinear(ctx, dryRun, state, prePullSkipLinearIDs)
		if err != nil {
			result.Success = false
			result.Error = err.Error()
			if jsonOutput {
				outputJSON(result)
			} else {
				fmt.Fprintf(os.Stderr, "Error pulling from Linear: %v\n", err)
			}
			os.Exit(1)
		}

		result.Stats.Pulled = pullStats.Created + pullStats.Updated
		result.Stats.Created += pullStats.Created
		result.Stats.Updated += pullStats.Updated
		result.Stats.Skipped += pullStats.Skipped

		if !dryRun {
			fmt.Printf("✓ Pulled %d issues (%d created, %d updated)\n",
				result.Stats.Pulled, pullStats.Created, pullStats.Updated)
		}
	}

	if pull && push {
		conflicts := prePullConflicts
		var err error
		if conflicts == nil {
			conflicts, err = detectLinearConflicts(ctx)
		}
		if err != nil {
			result.Warnings = append(result.Warnings, fmt.Sprintf("conflict detection failed: %v", err))
		} else if len(conflicts) > 0 {
			result.Stats.Conflicts = len(conflicts)
			if dryRun {
				if preferLocal {
					fmt.Printf("→ [DRY RUN] Would resolve %d conflicts (preferring local)\n", len(conflicts))
					forceUpdateIDs = make(map[string]bool, len(conflicts))
					for _, conflict := range conflicts {
						forceUpdateIDs[conflict.IssueID] = true
					}
				} else if preferLinear {
					fmt.Printf("→ [DRY RUN] Would resolve %d conflicts (preferring Linear)\n", len(conflicts))
					skipUpdateIDs = make(map[string]bool, len(conflicts))
					for _, conflict := range conflicts {
						skipUpdateIDs[conflict.IssueID] = true
					}
				} else {
					fmt.Printf("→ [DRY RUN] Would resolve %d conflicts (newer wins)\n", len(conflicts))
					var linearWins []linear.Conflict
					var localWins []linear.Conflict
					for _, conflict := range conflicts {
						if conflict.LinearUpdated.After(conflict.LocalUpdated) {
							linearWins = append(linearWins, conflict)
						} else {
							localWins = append(localWins, conflict)
						}
					}
					if len(localWins) > 0 {
						forceUpdateIDs = make(map[string]bool, len(localWins))
						for _, conflict := range localWins {
							forceUpdateIDs[conflict.IssueID] = true
						}
					}
					if len(linearWins) > 0 {
						skipUpdateIDs = make(map[string]bool, len(linearWins))
						for _, conflict := range linearWins {
							skipUpdateIDs[conflict.IssueID] = true
						}
					}
				}
			} else if preferLocal {
				fmt.Printf("→ Resolving %d conflicts (preferring local)\n", len(conflicts))
				if forceUpdateIDs == nil {
					forceUpdateIDs = make(map[string]bool, len(conflicts))
					for _, conflict := range conflicts {
						forceUpdateIDs[conflict.IssueID] = true
					}
				}
			} else if preferLinear {
				fmt.Printf("→ Resolving %d conflicts (preferring Linear)\n", len(conflicts))
				if skipUpdateIDs == nil {
					skipUpdateIDs = make(map[string]bool, len(conflicts))
					for _, conflict := range conflicts {
						skipUpdateIDs[conflict.IssueID] = true
					}
				}
				if prePullConflicts == nil {
					if err := reimportLinearConflicts(ctx, conflicts); err != nil {
						result.Warnings = append(result.Warnings, fmt.Sprintf("conflict resolution failed: %v", err))
					}
				}
			} else {
				fmt.Printf("→ Resolving %d conflicts (newer wins)\n", len(conflicts))
				if err := resolveLinearConflictsByTimestamp(ctx, conflicts); err != nil {
					result.Warnings = append(result.Warnings, fmt.Sprintf("conflict resolution failed: %v", err))
				}
			}
		}
	}

	if push {
		if dryRun {
			fmt.Println("→ [DRY RUN] Would push issues to Linear")
		} else {
			fmt.Println("→ Pushing issues to Linear...")
		}

		pushStats, err := doPushToLinear(ctx, dryRun, createOnly, updateRefs, forceUpdateIDs, skipUpdateIDs)
		if err != nil {
			result.Success = false
			result.Error = err.Error()
			if jsonOutput {
				outputJSON(result)
			} else {
				fmt.Fprintf(os.Stderr, "Error pushing to Linear: %v\n", err)
			}
			os.Exit(1)
		}

		result.Stats.Pushed = pushStats.Created + pushStats.Updated
		result.Stats.Created += pushStats.Created
		result.Stats.Updated += pushStats.Updated
		result.Stats.Skipped += pushStats.Skipped
		result.Stats.Errors += pushStats.Errors

		if !dryRun {
			fmt.Printf("✓ Pushed %d issues (%d created, %d updated)\n",
				result.Stats.Pushed, pushStats.Created, pushStats.Updated)
		}
	}

	if !dryRun && result.Success {
		result.LastSync = time.Now().Format(time.RFC3339)
		if err := store.SetConfig(ctx, "linear.last_sync", result.LastSync); err != nil {
			result.Warnings = append(result.Warnings, fmt.Sprintf("failed to update last_sync: %v", err))
		}
	}

	if jsonOutput {
		outputJSON(result)
	} else if dryRun {
		fmt.Println("\n✓ Dry run complete (no changes made)")
	} else {
		fmt.Println("\n✓ Linear sync complete")
		if len(result.Warnings) > 0 {
			fmt.Println("\nWarnings:")
			for _, w := range result.Warnings {
				fmt.Printf("  - %s\n", w)
			}
		}
	}
}

func runLinearStatus(cmd *cobra.Command, args []string) {
	ctx := rootCtx

	if err := ensureStoreActive(); err != nil {
		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
		os.Exit(1)
	}

	apiKey, _ := getLinearConfig(ctx, "linear.api_key")
	teamID, _ := getLinearConfig(ctx, "linear.team_id")
	lastSync, _ := store.GetConfig(ctx, "linear.last_sync")

	configured := apiKey != "" && teamID != ""

	allIssues, err := store.SearchIssues(ctx, "", types.IssueFilter{})
	if err != nil {
		fmt.Fprintf(os.Stderr, "Error: %v\n", err)
		os.Exit(1)
	}

	withLinearRef := 0
	pendingPush := 0
	for _, issue := range allIssues {
		if issue.ExternalRef != nil && linear.IsLinearExternalRef(*issue.ExternalRef) {
			withLinearRef++
		} else if issue.ExternalRef == nil {
			pendingPush++
		}
	}

	if jsonOutput {
		hasAPIKey := apiKey != ""
		outputJSON(map[string]interface{}{
			"configured":      configured,
			"has_api_key":     hasAPIKey,
			"team_id":         teamID,
			"last_sync":       lastSync,
			"total_issues":    len(allIssues),
			"with_linear_ref": withLinearRef,
			"pending_push":    pendingPush,
		})
		return
	}

	fmt.Println("Linear Sync Status")
	fmt.Println("==================")
	fmt.Println()

	if !configured {
		fmt.Println("Status: Not configured")
		fmt.Println()
		fmt.Println("To configure Linear integration:")
		fmt.Println("  bd config set linear.api_key \"YOUR_API_KEY\"")
		fmt.Println("  bd config set linear.team_id \"TEAM_ID\"")
		fmt.Println()
		fmt.Println("Or use environment variables:")
		fmt.Println("  export LINEAR_API_KEY=\"YOUR_API_KEY\"")
		fmt.Println("  export LINEAR_TEAM_ID=\"TEAM_ID\"")
		return
	}

	fmt.Printf("Team ID:      %s\n", teamID)
	fmt.Printf("API Key:      %s\n", maskAPIKey(apiKey))
	if lastSync != "" {
		fmt.Printf("Last Sync:    %s\n", lastSync)
	} else {
		fmt.Println("Last Sync:    Never")
	}
	fmt.Println()
	fmt.Printf("Total Issues: %d\n", len(allIssues))
	fmt.Printf("With Linear:  %d\n", withLinearRef)
	fmt.Printf("Local Only:   %d\n", pendingPush)

	if pendingPush > 0 {
		fmt.Println()
		fmt.Printf("Run 'bd linear sync --push' to push %d local issue(s) to Linear\n", pendingPush)
	}
}

func runLinearTeams(cmd *cobra.Command, args []string) {
	ctx := rootCtx

	apiKey, apiKeySource := getLinearConfig(ctx, "linear.api_key")
	if apiKey == "" {
		fmt.Fprintf(os.Stderr, "Error: Linear API key not configured\n")
		fmt.Fprintf(os.Stderr, "Run: bd config set linear.api_key \"YOUR_API_KEY\"\n")
		fmt.Fprintf(os.Stderr, "Or:  export LINEAR_API_KEY=YOUR_API_KEY\n")
		os.Exit(1)
	}

	debug.Logf("Using API key from %s", apiKeySource)

	client := linear.NewClient(apiKey, "")

	teams, err := client.FetchTeams(ctx)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Error fetching teams: %v\n", err)
		os.Exit(1)
	}

	if len(teams) == 0 {
		fmt.Println("No teams found (check your API key permissions)")
		return
	}

	if jsonOutput {
		outputJSON(teams)
		return
	}

	fmt.Println("Available Linear Teams")
	fmt.Println("======================")
	fmt.Println()
	fmt.Printf("%-40s  %-6s  %s\n", "ID (use this for linear.team_id)", "Key", "Name")
	fmt.Printf("%-40s  %-6s  %s\n", "----------------------------------------", "------", "----")
	for _, team := range teams {
		fmt.Printf("%-40s  %-6s  %s\n", team.ID, team.Key, team.Name)
	}
	fmt.Println()
	fmt.Println("To configure:")
	fmt.Println("  bd config set linear.team_id \"<ID>\"")
}

// uuidRegex matches valid UUID format (with or without hyphens).
var uuidRegex = regexp.MustCompile(`^[0-9a-fA-F]{8}-?[0-9a-fA-F]{4}-?[0-9a-fA-F]{4}-?[0-9a-fA-F]{4}-?[0-9a-fA-F]{12}$`)

func isValidUUID(s string) bool {
	return uuidRegex.MatchString(s)
}

// validateLinearConfig checks that required Linear configuration is present.
func validateLinearConfig() error {
	if err := ensureStoreActive(); err != nil {
		return fmt.Errorf("database not available: %w", err)
	}

	ctx := rootCtx

	apiKey, _ := getLinearConfig(ctx, "linear.api_key")
	if apiKey == "" {
		return fmt.Errorf("Linear API key not configured\nRun: bd config set linear.api_key \"YOUR_API_KEY\"\nOr: export LINEAR_API_KEY=YOUR_API_KEY")
	}

	teamID, _ := getLinearConfig(ctx, "linear.team_id")
	if teamID == "" {
		return fmt.Errorf("linear.team_id not configured\nRun: bd config set linear.team_id \"TEAM_ID\"\nOr: export LINEAR_TEAM_ID=TEAM_ID")
	}

	if !isValidUUID(teamID) {
		return fmt.Errorf("linear.team_id appears invalid (expected UUID format like '12345678-1234-1234-1234-123456789abc')\nCurrent value: %s", teamID)
	}

	return nil
}

// maskAPIKey returns a masked version of an API key for display.
// Shows first 4 and last 4 characters, with dots in between.
func maskAPIKey(key string) string {
	if len(key) <= 8 {
		return "****"
	}
	return key[:4] + "..." + key[len(key)-4:]
}

// getLinearConfig reads a Linear configuration value, handling both daemon mode
// (where store is nil) and direct mode. Returns the value and its source.
// Priority: project config > environment variable.
func getLinearConfig(ctx context.Context, key string) (value string, source string) {
	// Try to read from store (works in direct mode)
	if store != nil {
		value, _ = store.GetConfig(ctx, key)
		if value != "" {
			return value, "project config (bd config)"
		}
	} else if dbPath != "" {
		tempStore, err := sqlite.NewWithTimeout(ctx, dbPath, 5*time.Second)
		if err == nil {
			defer func() { _ = tempStore.Close() }()
			value, _ = tempStore.GetConfig(ctx, key)
			if value != "" {
				return value, "project config (bd config)"
			}
		}
	}

	// Fall back to environment variable
	envKey := linearConfigToEnvVar(key)
	if envKey != "" {
		value = os.Getenv(envKey)
		if value != "" {
			return value, fmt.Sprintf("environment variable (%s)", envKey)
		}
	}

	return "", ""
}

// linearConfigToEnvVar maps Linear config keys to their environment variable names.
func linearConfigToEnvVar(key string) string {
	switch key {
	case "linear.api_key":
		return "LINEAR_API_KEY"
	case "linear.team_id":
		return "LINEAR_TEAM_ID"
	default:
		return ""
	}
}

// getLinearClient creates a configured Linear client from beads config.
func getLinearClient(ctx context.Context) (*linear.Client, error) {
	apiKey, _ := getLinearConfig(ctx, "linear.api_key")
	if apiKey == "" {
		return nil, fmt.Errorf("Linear API key not configured")
	}

	teamID, _ := getLinearConfig(ctx, "linear.team_id")
	if teamID == "" {
		return nil, fmt.Errorf("Linear team ID not configured")
	}

	client := linear.NewClient(apiKey, teamID)

	if store != nil {
		if endpoint, _ := store.GetConfig(ctx, "linear.api_endpoint"); endpoint != "" {
			client = client.WithEndpoint(endpoint)
		}
		// Filter to specific project if configured
		if projectID, _ := store.GetConfig(ctx, "linear.project_id"); projectID != "" {
			client = client.WithProjectID(projectID)
		}
	}

	return client, nil
}

// storeConfigLoader adapts the store to the linear.ConfigLoader interface.
type storeConfigLoader struct {
	ctx context.Context
}

func (l *storeConfigLoader) GetAllConfig() (map[string]string, error) {
	return store.GetAllConfig(l.ctx)
}

// loadLinearMappingConfig loads mapping configuration from beads config.
func loadLinearMappingConfig(ctx context.Context) *linear.MappingConfig {
	if store == nil {
		return linear.DefaultMappingConfig()
	}
	return linear.LoadMappingConfig(&storeConfigLoader{ctx: ctx})
}

// getLinearIDMode returns the configured ID mode for Linear imports.
// Supported values: "hash" (default) or "db".
func getLinearIDMode(ctx context.Context) string {
	mode, _ := getLinearConfig(ctx, "linear.id_mode")
	mode = strings.ToLower(strings.TrimSpace(mode))
	if mode == "" {
		return "hash"
	}
	return mode
}

// getLinearHashLength returns the configured hash length for Linear imports.
// Values are clamped to the supported range 3-8.
func getLinearHashLength(ctx context.Context) int {
	raw, _ := getLinearConfig(ctx, "linear.hash_length")
	if raw == "" {
		return 6
	}
	value, err := strconv.Atoi(strings.TrimSpace(raw))
	if err != nil {
		return 6
	}
	if value < 3 {
		return 3
	}
	if value > 8 {
		return 8
	}
	return value
}