package cmd

import (
	"fmt"
	"os"
	"os/exec"
	"sort"
	"strings"
	"time"

	"git.jnss.me/joakim/opal/internal/engine"
	"github.com/spf13/cobra"
)

var editCmd = &cobra.Command{
	Use:   "edit [filter...]",
	Short: "Edit a task in $EDITOR",
	Long: `Opens a task in your $EDITOR for interactive modification.

Examples:
  opal edit 2              # Edit task with display ID 2
  opal 2 edit              # Flexible syntax (same as above)
  opal edit +urgent        # Edit task if only one matches`,
	Run: func(cmd *cobra.Command, args []string) {
		parsed := getParsedArgs(cmd)
		if err := editTask(parsed.Filters); err != nil {
			fmt.Fprintf(os.Stderr, "Error: %v\n", err)
			os.Exit(1)
		}
	},
}

func editTask(args []string) error {
	// Validate we have a filter
	if len(args) == 0 {
		return fmt.Errorf("no task specified for edit command")
	}

	// Parse filter
	filter, err := engine.ParseFilter(args)
	if err != nil {
		return fmt.Errorf("failed to parse filter: %w", err)
	}

	// Load working set to resolve IDs
	ws, err := engine.LoadWorkingSet()
	if err != nil {
		return fmt.Errorf("failed to load working set: %w", err)
	}

	// Resolve task
	var task *engine.Task

	if len(filter.IDs) > 0 {
		// Resolve display ID (should be exactly one)
		if len(filter.IDs) != 1 {
			return fmt.Errorf("edit requires exactly one task (specified %d IDs)", len(filter.IDs))
		}
		task, err = ws.GetTaskByDisplayID(filter.IDs[0])
		if err != nil {
			return err
		}
	} else {
		// Use filter to get tasks
		tasks, err := engine.GetTasks(filter)
		if err != nil {
			return fmt.Errorf("failed to get tasks: %w", err)
		}

		if len(tasks) == 0 {
			return fmt.Errorf("no task found matching filter")
		}
		if len(tasks) > 1 {
			return fmt.Errorf("edit requires exactly one task (filter matched %d tasks)", len(tasks))
		}

		task = tasks[0]
	}

	// Create temporary file
	tmpFile, err := os.CreateTemp("", "opal-task-*.txt")
	if err != nil {
		return fmt.Errorf("failed to create temp file: %w", err)
	}
	tmpPath := tmpFile.Name()
	defer os.Remove(tmpPath) // Clean up

	// Write task data to temp file
	content := generateEditableContent(task)
	if _, err := tmpFile.WriteString(content); err != nil {
		tmpFile.Close()
		return fmt.Errorf("failed to write temp file: %w", err)
	}
	tmpFile.Close()

	// Launch editor
	if err := launchEditor(tmpPath); err != nil {
		return err
	}

	// Parse edited content
	fields, err := parseEditedFile(tmpPath)
	if err != nil {
		return err
	}

	// Apply changes to task
	if err := applyEditedFields(task, fields); err != nil {
		return err
	}

	fmt.Printf("Task %s updated.\n", task.UUID)
	return nil
}

// generateEditableContent creates the editable text format
func generateEditableContent(task *engine.Task) string {
	var sb strings.Builder

	// Header with read-only info
	sb.WriteString(fmt.Sprintf("# Task UUID: %s (read-only)\n", task.UUID))
	sb.WriteString(fmt.Sprintf("# Created: %s (read-only)\n", formatTimeForEdit(task.Created)))
	sb.WriteString(fmt.Sprintf("# Modified: %s (read-only)\n", formatTimeForEdit(task.Modified)))

	if task.ParentUUID != nil {
		sb.WriteString(fmt.Sprintf("# Parent UUID: %s (this is a recurring task instance)\n", *task.ParentUUID))
		sb.WriteString("# Note: Changing 'recurrence' will update the template for future instances\n")
	}

	if task.End != nil {
		sb.WriteString(fmt.Sprintf("# End: %s (read-only, set on completion)\n", formatTimeForEdit(*task.End)))
	}

	sb.WriteString("#\n")
	sb.WriteString("# Edit the fields below. Lines starting with # are ignored.\n")
	sb.WriteString("# Leave a value empty to clear it.\n")
	sb.WriteString("# Status: pending, completed, deleted (recurring/template is system-managed)\n")
	sb.WriteString("# Priority: H (high), M (medium), L (low), D (default)\n")
	sb.WriteString("\n")

	// Editable fields
	sb.WriteString(fmt.Sprintf("description: %s\n", task.Description))
	sb.WriteString(fmt.Sprintf("status: %s\n", formatStatusForEdit(task.Status)))
	sb.WriteString(fmt.Sprintf("priority: %s\n", formatPriorityForEdit(task.Priority)))

	if task.Project != nil {
		sb.WriteString(fmt.Sprintf("project: %s\n", *task.Project))
	} else {
		sb.WriteString("project: \n")
	}

	if task.Due != nil {
		sb.WriteString(fmt.Sprintf("due: %s\n", formatTimeForEdit(*task.Due)))
	} else {
		sb.WriteString("due: \n")
	}

	if task.Scheduled != nil {
		sb.WriteString(fmt.Sprintf("scheduled: %s\n", formatTimeForEdit(*task.Scheduled)))
	} else {
		sb.WriteString("scheduled: \n")
	}

	if task.Wait != nil {
		sb.WriteString(fmt.Sprintf("wait: %s\n", formatTimeForEdit(*task.Wait)))
	} else {
		sb.WriteString("wait: \n")
	}

	if task.Until != nil {
		sb.WriteString(fmt.Sprintf("until: %s\n", formatTimeForEdit(*task.Until)))
	} else {
		sb.WriteString("until: \n")
	}

	if task.Start != nil {
		sb.WriteString(fmt.Sprintf("start: %s\n", formatTimeForEdit(*task.Start)))
	} else {
		sb.WriteString("start: \n")
	}

	// Recurrence - show template's recurrence or instance's parent recurrence
	var recurrenceValue string
	if task.RecurrenceDuration != nil {
		recurrenceValue = engine.FormatRecurrenceDuration(*task.RecurrenceDuration)
	} else if task.ParentUUID != nil {
		// Load parent to show its recurrence
		if parent, err := engine.GetTask(*task.ParentUUID); err == nil && parent.RecurrenceDuration != nil {
			recurrenceValue = engine.FormatRecurrenceDuration(*parent.RecurrenceDuration)
		}
	}
	sb.WriteString(fmt.Sprintf("recurrence: %s\n", recurrenceValue))

	// Tags
	if len(task.Tags) > 0 {
		sb.WriteString(fmt.Sprintf("tags: %s\n", strings.Join(task.Tags, ",")))
	} else {
		sb.WriteString("tags: \n")
	}

	return sb.String()
}

// parseEditedFile reads and parses the modified file
func parseEditedFile(filepath string) (map[string]string, error) {
	content, err := os.ReadFile(filepath)
	if err != nil {
		return nil, fmt.Errorf("failed to open edited file: %w", err)
	}
	return engine.ParseKeyValueFormat(string(content), true) // skip comments
}

// applyEditedFields applies parsed changes to task
func applyEditedFields(task *engine.Task, fields map[string]string) error {
	// Validate required fields
	description, hasDesc := fields["description"]
	if !hasDesc || strings.TrimSpace(description) == "" {
		return fmt.Errorf("description cannot be empty")
	}

	// Parse status
	var newStatus engine.Status
	if statusStr, ok := fields["status"]; ok && statusStr != "" {
		parsed, err := parseStatus(statusStr)
		if err != nil {
			return err
		}
		newStatus = parsed
	} else {
		newStatus = task.Status
	}

	// Handle status changes specially
	oldStatus := task.Status

	// If changing to completed, use Complete() method
	if newStatus == engine.StatusCompleted && oldStatus != engine.StatusCompleted {
		// Apply other fields first
		if err := applyNonStatusFields(task, fields); err != nil {
			return err
		}
		// Then complete (which saves automatically)
		_, err := task.Complete()
		return err
	}

	// If changing to deleted, use Delete() method
	if newStatus == engine.StatusDeleted && oldStatus != engine.StatusDeleted {
		// Apply other fields first
		if err := applyNonStatusFields(task, fields); err != nil {
			return err
		}
		// Then delete (which saves automatically)
		return task.Delete(false)
	}

	// If changing from completed/deleted to pending, clear end time
	if newStatus == engine.StatusPending && (oldStatus == engine.StatusCompleted || oldStatus == engine.StatusDeleted) {
		task.Status = engine.StatusPending
		task.End = nil
	} else {
		task.Status = newStatus
	}

	// Apply all other fields
	if err := applyNonStatusFields(task, fields); err != nil {
		return err
	}

	// Save the task
	return task.Save()
}

// applyNonStatusFields applies all fields except status
func applyNonStatusFields(task *engine.Task, fields map[string]string) error {
	// Description
	if desc, ok := fields["description"]; ok {
		task.Description = desc
	}

	// Priority
	if priStr, ok := fields["priority"]; ok && priStr != "" {
		pri, err := parsePriority(priStr)
		if err != nil {
			return err
		}
		task.Priority = pri
	}

	// Project
	if proj, ok := fields["project"]; ok {
		if proj == "" {
			task.Project = nil
		} else {
			task.Project = &proj
		}
	}

	// Date fields
	dateFields := map[string]**time.Time{
		"due":       &task.Due,
		"scheduled": &task.Scheduled,
		"wait":      &task.Wait,
		"until":     &task.Until,
		"start":     &task.Start,
	}

	for fieldName, taskField := range dateFields {
		if dateStr, ok := fields[fieldName]; ok {
			if dateStr == "" {
				*taskField = nil
			} else {
				parsed, err := engine.ParseDate(dateStr)
				if err != nil {
					return fmt.Errorf("invalid date for '%s': %w", fieldName, err)
				}
				*taskField = &parsed
			}
		}
	}

	// Recurrence
	if recurStr, ok := fields["recurrence"]; ok {
		if recurStr == "" {
			// Clear recurrence
			if task.ParentUUID != nil {
				// This is an instance - clear parent's recurrence
				parent, err := engine.GetTask(*task.ParentUUID)
				if err != nil {
					return fmt.Errorf("failed to load parent task: %w", err)
				}
				parent.RecurrenceDuration = nil
				if err := parent.Save(); err != nil {
					return fmt.Errorf("failed to update parent recurrence: %w", err)
				}
				fmt.Println("Cleared recurrence pattern (no more instances will be spawned)")
			} else {
				task.RecurrenceDuration = nil
			}
		} else {
			// Parse recurrence
			duration, err := engine.ParseRecurrencePattern(recurStr)
			if err != nil {
				return fmt.Errorf("invalid recurrence pattern: %w", err)
			}

			if task.ParentUUID != nil {
				// This is an instance - update parent's recurrence
				parent, err := engine.GetTask(*task.ParentUUID)
				if err != nil {
					return fmt.Errorf("failed to load parent task: %w", err)
				}
				parent.RecurrenceDuration = &duration
				if err := parent.Save(); err != nil {
					return fmt.Errorf("failed to update parent recurrence: %w", err)
				}
				fmt.Println("Updated recurrence pattern for future instances")
			} else {
				// This is a regular task or template
				task.RecurrenceDuration = &duration
			}
		}
	}

	// Tags - replace all tags
	if tagsStr, ok := fields["tags"]; ok {
		// Remove all existing tags
		for _, tag := range task.Tags {
			if err := task.RemoveTag(tag); err != nil {
				return fmt.Errorf("failed to remove tag '%s': %w", tag, err)
			}
		}

		// Add new tags
		if tagsStr != "" {
			newTags := parseTags(tagsStr)
			for _, tag := range newTags {
				if err := task.AddTag(tag); err != nil {
					return fmt.Errorf("failed to add tag '%s': %w", tag, err)
				}
			}
		}
	}

	return nil
}

// getEditor returns the editor command ($EDITOR or 'vi')
func getEditor() string {
	if editor := os.Getenv("EDITOR"); editor != "" {
		return editor
	}
	return "vi"
}

// launchEditor opens file in editor and waits
func launchEditor(filepath string) error {
	editor := getEditor()

	cmd := exec.Command(editor, filepath)
	cmd.Stdin = os.Stdin
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr

	if err := cmd.Run(); err != nil {
		if exitErr, ok := err.(*exec.ExitError); ok {
			return fmt.Errorf("editor exited with error (code %d)", exitErr.ExitCode())
		}
		return fmt.Errorf("failed to run editor: %w", err)
	}

	return nil
}

// parsePriority converts H/M/L/D to Priority constant
func parsePriority(s string) (engine.Priority, error) {
	switch strings.ToUpper(strings.TrimSpace(s)) {
	case "H":
		return engine.PriorityHigh, nil
	case "M":
		return engine.PriorityMedium, nil
	case "L":
		return engine.PriorityLow, nil
	case "D", "":
		return engine.PriorityDefault, nil
	default:
		return engine.PriorityDefault, fmt.Errorf("invalid priority '%s' (must be H, M, L, or D)", s)
	}
}

// parseStatus converts string to Status constant
func parseStatus(s string) (engine.Status, error) {
	switch strings.ToLower(strings.TrimSpace(s)) {
	case "pending":
		return engine.StatusPending, nil
	case "completed":
		return engine.StatusCompleted, nil
	case "deleted":
		return engine.StatusDeleted, nil
	case "recurring", "template":
		// Accept these but keep them unchanged (system-managed status)
		return engine.StatusRecurring, nil
	default:
		return engine.StatusPending, fmt.Errorf("invalid status '%s' (must be: pending, completed, deleted, or recurring)", s)
	}
}

// parseTags splits comma-separated tags
func parseTags(s string) []string {
	if s == "" {
		return []string{}
	}

	parts := strings.Split(s, ",")
	tags := make([]string, 0, len(parts))
	for _, part := range parts {
		tag := strings.TrimSpace(part)
		if tag != "" {
			tags = append(tags, tag)
		}
	}
	sort.Strings(tags) // Sort alphabetically for consistency
	return tags
}

// formatTimeForEdit formats a time for the edit file
func formatTimeForEdit(t time.Time) string {
	// Check if time component is at midnight (00:00)
	if t.Hour() == 0 && t.Minute() == 0 {
		// Date only, no time component
		return t.Format("2006-01-02")
	}
	// Date with time - use colon format that parser understands
	return t.Format("2006-01-02:15:04")
}

// formatStatusForEdit formats status for the edit file
func formatStatusForEdit(s engine.Status) string {
	switch s {
	case engine.StatusPending:
		return "pending"
	case engine.StatusCompleted:
		return "completed"
	case engine.StatusDeleted:
		return "deleted"
	case engine.StatusRecurring:
		return "recurring"
	default:
		return "pending"
	}
}

// formatPriorityForEdit formats priority for the edit file
func formatPriorityForEdit(p engine.Priority) string {
	switch p {
	case engine.PriorityHigh:
		return "H"
	case engine.PriorityMedium:
		return "M"
	case engine.PriorityLow:
		return "L"
	case engine.PriorityDefault:
		return "D"
	default:
		return "D"
	}
}