package parser

import (
	"bufio"
	"os"
	"regexp"
	"strings"

	"github.com/rwejlgaard/org/internal/model"
)

// Parser patterns
var (
	headingPattern   = regexp.MustCompile(`^(\*+)\s+(?:(TODO|PROG|BLOCK|DONE)\s+)?(.+)$`)
	scheduledPattern = regexp.MustCompile(`SCHEDULED:\s*<([^>]+)>`)
	deadlinePattern  = regexp.MustCompile(`DEADLINE:\s*<([^>]+)>`)
	clockPattern     = regexp.MustCompile(`CLOCK:\s*\[([^\]]+)\](?:--\[([^\]]+)\])?`)
	drawerStart      = regexp.MustCompile(`^\s*:LOGBOOK:\s*$`)
	drawerEnd        = regexp.MustCompile(`^\s*:END:\s*$`)
	codeBlockStart   = regexp.MustCompile(`^\s*#\+BEGIN_SRC`)
	codeBlockEnd     = regexp.MustCompile(`^\s*#\+END_SRC`)
)

// ParseOrgFile reads and parses an org-mode file
func ParseOrgFile(path string) (*model.OrgFile, error) {
	file, err := os.Open(path)
	if err != nil {
		// If file doesn't exist, return empty org file
		if os.IsNotExist(err) {
			return &model.OrgFile{Path: path, Items: []*model.Item{}}, nil
		}
		return nil, err
	}
	defer file.Close()

	orgFile := &model.OrgFile{Path: path, Items: []*model.Item{}}
	scanner := bufio.NewScanner(file)

	var currentItem *model.Item
	var itemStack []*model.Item // Stack to track parent items
	var inCodeBlock bool
	var inLogbookDrawer bool

	for scanner.Scan() {
		line := scanner.Text()

		// Check for drawer boundaries
		if drawerStart.MatchString(line) {
			inLogbookDrawer = true
			if currentItem != nil {
				currentItem.Notes = append(currentItem.Notes, line)
			}
			continue
		}
		if drawerEnd.MatchString(line) && inLogbookDrawer {
			inLogbookDrawer = false
			if currentItem != nil {
				currentItem.Notes = append(currentItem.Notes, line)
			}
			continue
		}

		// Check for code block boundaries
		if codeBlockStart.MatchString(line) {
			inCodeBlock = true
			if currentItem != nil {
				currentItem.Notes = append(currentItem.Notes, line)
			}
			continue
		}
		if codeBlockEnd.MatchString(line) {
			inCodeBlock = false
			if currentItem != nil {
				currentItem.Notes = append(currentItem.Notes, line)
			}
			continue
		}

		// If in code block, add line to notes
		if inCodeBlock {
			if currentItem != nil {
				currentItem.Notes = append(currentItem.Notes, line)
			}
			continue
		}

		// Try to match heading
		if matches := headingPattern.FindStringSubmatch(line); matches != nil {
			level := len(matches[1])
			state := model.TodoState(matches[2])
			title := matches[3]

			item := &model.Item{
				Level:    level,
				State:    state,
				Title:    title,
				Notes:    []string{},
				Children: []*model.Item{},
			}

			// Find parent based on level
			for len(itemStack) > 0 && itemStack[len(itemStack)-1].Level >= level {
				itemStack = itemStack[:len(itemStack)-1]
			}

			if len(itemStack) == 0 {
				// Top-level item
				orgFile.Items = append(orgFile.Items, item)
			} else {
				// Child item
				parent := itemStack[len(itemStack)-1]
				parent.Children = append(parent.Children, item)
			}

			itemStack = append(itemStack, item)
			currentItem = item
		} else if currentItem != nil {
			// This is content under the current item
			trimmed := strings.TrimSpace(line)

			// Check for SCHEDULED
			if matches := scheduledPattern.FindStringSubmatch(line); matches != nil {
				if t, err := parseOrgDate(matches[1]); err == nil {
					currentItem.Scheduled = &t
				}
			}

			// Check for DEADLINE
			if matches := deadlinePattern.FindStringSubmatch(line); matches != nil {
				if t, err := parseOrgDate(matches[1]); err == nil {
					currentItem.Deadline = &t
				}
			}

			// Check for CLOCK (can be inside or outside drawer)
			if matches := clockPattern.FindStringSubmatch(line); matches != nil {
				if startTime, err := parseClockTimestamp(matches[1]); err == nil {
					entry := model.ClockEntry{Start: startTime}
					if len(matches) > 2 && matches[2] != "" {
						if endTime, err := parseClockTimestamp(matches[2]); err == nil {
							entry.End = &endTime
						}
					}
					currentItem.ClockEntries = append(currentItem.ClockEntries, entry)
				}
			}

			// Add all lines as notes (including scheduling lines and drawer content for proper serialization)
			if trimmed != "" || len(currentItem.Notes) > 0 {
				currentItem.Notes = append(currentItem.Notes, line)
			}
		}
	}

	if err := scanner.Err(); err != nil {
		return nil, err
	}

	return orgFile, nil
}