// Package parser provides Architecture parsing based on architectureParser.ts
package parser

import (
	"fmt"
	"strings"

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

// ArchitectureParser implements Architecture parsing
type ArchitectureParser struct {
	tokens  []lexer.Token
	current int
	diagram *ast.ArchitectureDiagram
}

// NewArchitectureParser creates a new Architecture parser
func NewArchitectureParser() *ArchitectureParser {
	return &ArchitectureParser{
		diagram: ast.NewArchitectureDiagram(),
	}
}

// Parse parses Architecture syntax
func (p *ArchitectureParser) Parse(input string) (*ast.ArchitectureDiagram, 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.NewArchitectureDiagram()

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

	return p.diagram, nil
}

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

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

	return nil
}

// parseStatement parses individual Architecture statements
func (p *ArchitectureParser) 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("service"):
		return p.parseService()
	case p.checkKeyword("group"):
		return p.parseGroup()
	case p.check(lexer.TokenID):
		// Could be service definition or edge
		return p.parseServiceOrEdge()
	default:
		token := p.peek()
		return p.error(fmt.Sprintf("unexpected token: %s", token.Value))
	}
}

// parseTitle parses title statements
func (p *ArchitectureParser) 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
}

// parseService parses service statements
func (p *ArchitectureParser) parseService() error {
	p.advance() // consume 'service'

	if !p.check(lexer.TokenID) {
		return p.error("expected service ID")
	}

	serviceID := p.advance().Value

	service := &ast.ArchitectureService{
		ID: serviceID,
	}

	// Parse optional service properties
	for !p.check(lexer.TokenNewline) && !p.isAtEnd() {
		if p.check(lexer.TokenOpenBracket) {
			p.advance() // consume '['

			// Parse service title
			var titleParts []string
			for !p.check(lexer.TokenCloseBracket) && !p.isAtEnd() {
				titleParts = append(titleParts, p.advance().Value)
			}

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

			if p.check(lexer.TokenCloseBracket) {
				p.advance() // consume ']'
			}
		} else if p.checkKeyword("in") {
			p.advance() // consume 'in'
			if p.check(lexer.TokenID) {
				groupID := p.advance().Value
				service.In = &groupID
			}
		} else {
			p.advance() // consume unknown token
		}
	}

	p.diagram.Services = append(p.diagram.Services, service)
	return nil
}

// parseGroup parses group statements
func (p *ArchitectureParser) parseGroup() error {
	p.advance() // consume 'group'

	if !p.check(lexer.TokenID) {
		return p.error("expected group ID")
	}

	groupID := p.advance().Value

	group := &ast.ArchitectureGroup{
		ID: groupID,
	}

	// Parse optional group properties
	for !p.check(lexer.TokenNewline) && !p.isAtEnd() {
		if p.check(lexer.TokenOpenBracket) {
			p.advance() // consume '['

			// Parse group title
			var titleParts []string
			for !p.check(lexer.TokenCloseBracket) && !p.isAtEnd() {
				titleParts = append(titleParts, p.advance().Value)
			}

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

			if p.check(lexer.TokenCloseBracket) {
				p.advance() // consume ']'
			}
		} else if p.checkKeyword("in") {
			p.advance() // consume 'in'
			if p.check(lexer.TokenID) {
				parentID := p.advance().Value
				group.In = &parentID
			}
		} else {
			p.advance() // consume unknown token
		}
	}

	p.diagram.Groups = append(p.diagram.Groups, group)
	return nil
}

// parseServiceOrEdge parses service definition or edge
func (p *ArchitectureParser) parseServiceOrEdge() error {
	serviceID := p.advance().Value

	// Check if this is an edge (has direction indicators)
	if p.checkDirection() {
		return p.parseEdge(serviceID)
	}

	// Otherwise, it's a simple service definition
	service := &ast.ArchitectureService{
		ID: serviceID,
	}

	// Parse optional service properties
	for !p.check(lexer.TokenNewline) && !p.isAtEnd() {
		if p.check(lexer.TokenOpenBracket) {
			p.advance() // consume '['

			// Parse service title
			var titleParts []string
			for !p.check(lexer.TokenCloseBracket) && !p.isAtEnd() {
				titleParts = append(titleParts, p.advance().Value)
			}

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

			if p.check(lexer.TokenCloseBracket) {
				p.advance() // consume ']'
			}
		} else {
			p.advance() // consume unknown token
		}
	}

	p.diagram.Services = append(p.diagram.Services, service)
	return nil
}

// parseEdge parses edge connections
func (p *ArchitectureParser) parseEdge(lhsID string) error {
	// Parse left direction
	lhsDir := p.parseDirection()

	// Skip connection symbols
	for p.check(lexer.TokenMinus) || p.check(lexer.TokenEquals) {
		p.advance()
	}

	// Parse right direction
	rhsDir := p.parseDirection()

	// Parse target service/group
	if !p.check(lexer.TokenID) {
		return p.error("expected target service/group ID")
	}

	rhsID := p.advance().Value

	edge := &ast.ArchitectureEdge{
		LhsID:  lhsID,
		LhsDir: lhsDir,
		RhsID:  rhsID,
		RhsDir: rhsDir,
	}

	// Parse optional edge title
	if p.check(lexer.TokenColon) {
		p.advance() // consume ':'

		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, " "))
			edge.Title = &title
		}
	}

	p.diagram.Edges = append(p.diagram.Edges, edge)
	return nil
}

// checkDirection checks if current token is a direction indicator
func (p *ArchitectureParser) checkDirection() bool {
	if p.isAtEnd() {
		return false
	}
	token := p.peek()
	return token.Type == lexer.TokenID &&
		(token.Value == "L" || token.Value == "R" || token.Value == "T" || token.Value == "B")
}

// parseDirection parses direction indicators
func (p *ArchitectureParser) parseDirection() ast.ArchitectureDirection {
	if !p.check(lexer.TokenID) {
		return ast.ArchitectureDirectionRight // default
	}

	token := p.advance()
	switch token.Value {
	case "L":
		return ast.ArchitectureDirectionLeft
	case "R":
		return ast.ArchitectureDirectionRight
	case "T":
		return ast.ArchitectureDirectionTop
	case "B":
		return ast.ArchitectureDirectionBottom
	default:
		return ast.ArchitectureDirectionRight // default
	}
}

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

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

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

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

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

func (p *ArchitectureParser) 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())
}