// Package parser provides Gantt chart parsing based on gantt.jison
package parser

import (
	"fmt"
	"strings"

	"mermaid-go/pkg/ast"
	"mermaid-go/pkg/lexer"
)

// GanttParser implements Gantt chart parsing following gantt.jison
type GanttParser struct {
	tokens  []lexer.Token
	current int
	diagram *ast.GanttDiagram
}

// NewGanttParser creates a new Gantt parser
func NewGanttParser() *GanttParser {
	return &GanttParser{
		diagram: &ast.GanttDiagram{
			DateFormat: "YYYY-MM-DD",
			AxisFormat: "%Y-%m-%d",
			Sections:   make([]*ast.GanttSection, 0),
			Tasks:      make([]*ast.GanttTask, 0),
			Config:     make(map[string]any),
		},
	}
}

// Parse parses Gantt chart syntax
func (p *GanttParser) Parse(input string) (*ast.GanttDiagram, error) {
	// Tokenize
	l := lexer.NewLexer(input)
	tokens, err := l.Tokenize()
	if err != nil {
		return nil, fmt.Errorf("lexical analysis failed: %w", err)
	}

	// Filter tokens
	p.tokens = lexer.FilterTokens(tokens)
	p.current = 0
	p.diagram = &ast.GanttDiagram{
		DateFormat: "YYYY-MM-DD",
		AxisFormat: "%Y-%m-%d",
		Sections:   make([]*ast.GanttSection, 0),
		Tasks:      make([]*ast.GanttTask, 0),
		Config:     make(map[string]any),
	}

	// Parse document
	err = p.parseDocument()
	if err != nil {
		return nil, fmt.Errorf("syntax analysis failed: %w", err)
	}

	return p.diagram, nil
}

// parseDocument parses the Gantt chart document
func (p *GanttParser) parseDocument() error {
	// Expect gantt
	if !p.check(lexer.TokenID) || p.peek().Value != "gantt" {
		return p.error("expected 'gantt'")
	}
	p.advance()

	// Parse statements
	for !p.isAtEnd() {
		if err := p.parseStatement(); err != nil {
			return err
		}
	}

	return nil
}

// parseStatement parses individual Gantt chart statements
func (p *GanttParser) parseStatement() error {
	if p.isAtEnd() {
		return nil
	}

	switch {
	case p.check(lexer.TokenNewline):
		p.advance() // Skip newlines
		return nil
	case p.checkKeyword("title"):
		return p.parseTitle()
	case p.checkKeyword("dateFormat"):
		return p.parseDateFormat()
	case p.checkKeyword("axisFormat"):
		return p.parseAxisFormat()
	case p.checkKeyword("section"):
		return p.parseSection()
	case p.check(lexer.TokenID):
		// Task definition
		return p.parseTask()
	default:
		token := p.peek()
		return p.error(fmt.Sprintf("unexpected token: %s", token.Value))
	}
}

// parseTitle parses title statements
func (p *GanttParser) parseTitle() error {
	p.advance() // consume 'title'

	var titleParts []string
	for !p.check(lexer.TokenNewline) && !p.isAtEnd() {
		titleParts = append(titleParts, p.advance().Value)
	}

	if len(titleParts) > 0 {
		title := strings.TrimSpace(strings.Join(titleParts, " "))
		p.diagram.Title = &title
	}

	return nil
}

// parseDateFormat parses dateFormat statements
func (p *GanttParser) parseDateFormat() error {
	p.advance() // consume 'dateFormat'

	var formatParts []string
	for !p.check(lexer.TokenNewline) && !p.isAtEnd() {
		formatParts = append(formatParts, p.advance().Value)
	}

	if len(formatParts) > 0 {
		p.diagram.DateFormat = strings.TrimSpace(strings.Join(formatParts, " "))
	}

	return nil
}

// parseAxisFormat parses axisFormat statements
func (p *GanttParser) parseAxisFormat() error {
	p.advance() // consume 'axisFormat'

	var formatParts []string
	for !p.check(lexer.TokenNewline) && !p.isAtEnd() {
		formatParts = append(formatParts, p.advance().Value)
	}

	if len(formatParts) > 0 {
		p.diagram.AxisFormat = strings.TrimSpace(strings.Join(formatParts, " "))
	}

	return nil
}

// parseSection parses section statements
func (p *GanttParser) parseSection() error {
	p.advance() // consume 'section'

	var sectionParts []string
	for !p.check(lexer.TokenNewline) && !p.isAtEnd() {
		sectionParts = append(sectionParts, p.advance().Value)
	}

	if len(sectionParts) > 0 {
		sectionName := strings.TrimSpace(strings.Join(sectionParts, " "))
		section := &ast.GanttSection{
			Name:  sectionName,
			Tasks: make([]*ast.GanttTask, 0),
		}
		p.diagram.Sections = append(p.diagram.Sections, section)
	}

	return nil
}

// parseTask parses task definitions
func (p *GanttParser) parseTask() error {
	// Parse task name
	taskName := p.advance().Value

	// Expect colon
	if !p.check(lexer.TokenColon) {
		return p.error("expected ':' after task name")
	}
	p.advance()

	// Parse task data
	var taskDataParts []string
	for !p.check(lexer.TokenNewline) && !p.isAtEnd() {
		taskDataParts = append(taskDataParts, p.advance().Value)
	}

	taskData := strings.TrimSpace(strings.Join(taskDataParts, " "))

	// Parse task data components
	task := &ast.GanttTask{
		ID:           generateTaskID(taskName),
		Name:         taskName,
		Status:       ast.GanttStatusActive,
		Dependencies: make([]string, 0),
	}

	// Parse task data (status, dates, dependencies)
	if taskData != "" {
		parts := strings.Fields(taskData)
		for _, part := range parts {
			part = strings.TrimSpace(part)
			if part == "" {
				continue
			}

			// Check for status keywords
			switch strings.ToLower(part) {
			case "active":
				task.Status = ast.GanttStatusActive
			case "done":
				task.Status = ast.GanttStatusDone
			case "crit":
				task.Status = ast.GanttStatusCrit
			default:
				// Try to parse as date or duration
				if strings.Contains(part, "-") && len(part) >= 8 {
					// Looks like a date
					if task.Start == nil {
						task.Start = &part
					} else if task.End == nil {
						task.End = &part
					}
				} else if strings.HasSuffix(part, "d") || strings.HasSuffix(part, "w") {
					// Looks like a duration
					task.Duration = &part
				}
			}
		}
	}

	// Add task to current section or global tasks
	if len(p.diagram.Sections) > 0 {
		currentSection := p.diagram.Sections[len(p.diagram.Sections)-1]
		currentSection.Tasks = append(currentSection.Tasks, task)
	}
	p.diagram.Tasks = append(p.diagram.Tasks, task)

	return nil
}

// generateTaskID generates a unique task ID from task name
func generateTaskID(name string) string {
	// Simple ID generation - replace spaces with underscores and make lowercase
	id := strings.ToLower(strings.ReplaceAll(name, " ", "_"))
	return id
}

// Helper methods
func (p *GanttParser) check(tokenType lexer.TokenType) bool {
	if p.isAtEnd() {
		return false
	}
	return p.peek().Type == tokenType
}

func (p *GanttParser) checkKeyword(keyword string) bool {
	if p.isAtEnd() {
		return false
	}
	token := p.peek()
	return token.Type == lexer.TokenID && strings.ToLower(token.Value) == strings.ToLower(keyword)
}

func (p *GanttParser) advance() lexer.Token {
	if !p.isAtEnd() {
		p.current++
	}
	return p.previous()
}

func (p *GanttParser) isAtEnd() bool {
	return p.current >= len(p.tokens) || p.peek().Type == lexer.TokenEOF
}

func (p *GanttParser) peek() lexer.Token {
	if p.current >= len(p.tokens) {
		return lexer.Token{Type: lexer.TokenEOF}
	}
	return p.tokens[p.current]
}

func (p *GanttParser) previous() lexer.Token {
	if p.current <= 0 {
		return lexer.Token{Type: lexer.TokenEOF}
	}
	return p.tokens[p.current-1]
}

func (p *GanttParser) error(message string) error {
	token := p.peek()
	return fmt.Errorf("parse error at line %d, column %d: %s (got %s)",
		token.Line, token.Column, message, token.Type.String())
}