package config

import (
	"fmt"
	"io"
)

// Parser parses configuration files
type Parser struct {
	scanner       *Scanner
	config        *Config
	currentObject map[string]any
	stack         []map[string]any
}

// NewParser creates a new parser with a reader and empty config
func NewParser(r io.Reader) *Parser {
	config := NewConfig()
	return &Parser{
		scanner:       NewScanner(r),
		config:        config,
		currentObject: config.data,
		stack:         make([]map[string]any, 0, 8), // Pre-allocate stack with reasonable capacity
	}
}

// Error creates an error with line information from the scanner
func (p *Parser) Error(msg string) error {
	return fmt.Errorf("line %d: %s", p.scanner.line, msg)
}

// Parse parses the config file and returns a Config
func (p *Parser) Parse() (*Config, error) {
	err := p.parseContent()
	if err != nil {
		return nil, err
	}
	return p.config, nil
}

// pushObject enters a new object scope
func (p *Parser) pushObject(obj map[string]any) {
	p.stack = append(p.stack, p.currentObject)
	p.currentObject = obj
}

// popObject exits the current object scope
func (p *Parser) popObject() {
	n := len(p.stack)
	if n > 0 {
		p.currentObject = p.stack[n-1]
		p.stack = p.stack[:n-1]
	}
}

// parseContent is the main parsing function
func (p *Parser) parseContent() error {
	skipErr := p.scanner.SkipWhitespace()
	for ; skipErr == nil; skipErr = p.scanner.SkipWhitespace() {
		r, peekErr := p.scanner.PeekRune()
		if peekErr == io.EOF {
			break
		}
		if peekErr != nil {
			return peekErr
		}

		// Handle comments
		if r == '-' {
			if err := p.scanner.ScanComment(); err != nil {
				return err
			}
			continue
		}

		// Handle name=value pairs or named objects
		if isLetter(r) {
			name, err := p.scanner.ScanName()
			if err != nil {
				return err
			}

			if err = p.scanner.SkipWhitespace(); err != nil {
				return err
			}

			r, err = p.scanner.PeekRune()
			if err != nil && err != io.EOF {
				return err
			}

			// Assignment or direct map/array
			if r == '=' {
				// It's a standard key=value pair
				p.scanner.ReadRune() // consume '='

				if err = p.scanner.SkipWhitespace(); err != nil {
					return err
				}

				value, err := p.scanner.ScanValue()
				if err != nil {
					return err
				}

				// Store the value directly
				if mapValue, ok := value.(map[string]any); ok {
					// Add an entry in current object
					newMap := make(map[string]any, 8) // Pre-allocate with capacity
					p.currentObject[name] = newMap

					// Process the map contents
					p.pushObject(newMap)

					// Copy values from scanned map to our object
					for k, v := range mapValue {
						p.currentObject[k] = v
					}

					p.popObject()
				} else {
					// Direct storage for primitives and arrays
					p.currentObject[name] = value
				}
			} else if r == '{' {
				// It's a map/array without '='
				value, err := p.scanner.ScanValue()
				if err != nil {
					return err
				}

				// Store the complex value directly
				if mapValue, ok := value.(map[string]any); ok {
					// Add an entry in current object
					newMap := make(map[string]any, 8) // Pre-allocate with capacity
					p.currentObject[name] = newMap

					// Process the map contents
					p.pushObject(newMap)

					// Copy values from scanned map to our object
					for k, v := range mapValue {
						p.currentObject[k] = v
					}

					p.popObject()
				} else {
					// Direct storage for arrays
					p.currentObject[name] = value
				}
			} else {
				return p.Error("expected '=' or '{' after name")
			}

			continue
		}

		return p.Error("unexpected character")
	}

	if skipErr != nil && skipErr != io.EOF {
		return skipErr
	}

	return nil
}

// Helper function
func isLetter(r rune) bool {
	return (r >= 'a' && r <= 'z') || (r >= 'A' && r <= 'Z')
}