Fin/parser.go

package config

import (
	"fmt"
	"io"
	"strconv"
)

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

// 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 current token
func (p *Parser) Error(msg string) error {
	return fmt.Errorf("line %d, column %d: %s",
		p.currentToken.Line, p.currentToken.Column, 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
}

// nextToken gets the next meaningful token (skipping comments)
func (p *Parser) nextToken() (Token, error) {
	for {
		token, err := p.scanner.NextToken()
		if err != nil {
			return token, err
		}

		// Skip comment tokens
		if token.Type != TokenComment {
			p.currentToken = token
			return token, nil
		}
	}
}

// parseContent is the main parsing function
func (p *Parser) parseContent() error {
	for {
		token, err := p.nextToken()
		if err != nil {
			return err
		}

		// Check for end of file
		if token.Type == TokenEOF {
			break
		}

		// We expect top level entries to be names
		if token.Type != TokenName {
			return p.Error("expected name at top level")
		}

		// Get the property name
		name := string(token.Value)

		// Get the next token (should be = or {)
		token, err = p.nextToken()
		if err != nil {
			return err
		}

		var value any

		if token.Type == TokenEquals {
			// It's a standard key=value assignment
			value, err = p.parseValue()
			if err != nil {
				return err
			}
		} else if token.Type == TokenOpenBrace {
			// It's a map/array without '='
			value, err = p.parseObject()
			if err != nil {
				return err
			}
		} else {
			return p.Error("expected '=' or '{' after name")
		}

		// Store the value in the config
		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.stack = append(p.stack, p.currentObject)
			p.currentObject = newMap

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

			// Restore parent object
			n := len(p.stack)
			if n > 0 {
				p.currentObject = p.stack[n-1]
				p.stack = p.stack[:n-1]
			}
		} else {
			// Direct storage for primitives and arrays
			p.currentObject[name] = value
		}
	}

	return nil
}

// parseValue parses a value after an equals sign
func (p *Parser) parseValue() (any, error) {
	token, err := p.nextToken()
	if err != nil {
		return nil, err
	}

	switch token.Type {
	case TokenString:
		return string(token.Value), nil

	case TokenNumber:
		strValue := string(token.Value)
		for i := 0; i < len(strValue); i++ {
			if strValue[i] == '.' {
				// It's a float
				val, err := strconv.ParseFloat(strValue, 64)
				if err != nil {
					return nil, p.Error(fmt.Sprintf("invalid float: %s", strValue))
				}
				return val, nil
			}
		}
		// It's an integer
		val, err := strconv.ParseInt(strValue, 10, 64)
		if err != nil {
			return nil, p.Error(fmt.Sprintf("invalid integer: %s", strValue))
		}
		return val, nil

	case TokenBoolean:
		return string(token.Value) == "true", nil

	case TokenOpenBrace:
		// It's a map or array
		return p.parseObject()

	case TokenName:
		// Treat as a string value
		return string(token.Value), nil

	default:
		return nil, p.Error(fmt.Sprintf("unexpected token: %v", token.Type))
	}
}

// parseObject parses a map or array
func (p *Parser) parseObject() (any, error) {
	contents := make(map[string]any)
	var arrayElements []any
	isArray := true

	for {
		token, err := p.nextToken()
		if err != nil {
			return nil, err
		}

		// Check for end of object
		if token.Type == TokenCloseBrace {
			if isArray && len(contents) == 0 {
				return arrayElements, nil
			}
			return contents, nil
		}

		// Handle based on token type
		switch token.Type {
		case TokenName:
			// Get the name value
			name := string(token.Value)

			// Get the next token to determine if it's a map entry or array element
			nextToken, err := p.nextToken()
			if err != nil {
				return nil, err
			}

			if nextToken.Type == TokenEquals {
				// It's a key-value pair
				value, err := p.parseValue()
				if err != nil {
					return nil, err
				}

				isArray = false
				contents[name] = value
			} else if nextToken.Type == TokenOpenBrace {
				// It's a nested object
				objValue, err := p.parseObject()
				if err != nil {
					return nil, err
				}

				isArray = false
				contents[name] = objValue
			} else {
				// Put the token back and treat the name as an array element
				p.scanner.UnreadToken(nextToken)

				// Convert to appropriate type if possible
				var value any = name

				// Try to infer type
				if name == "true" {
					value = true
				} else if name == "false" {
					value = false
				} else if isDigitOrMinus(name) {
					// Try to parse as number
					numValue, err := parseStringAsNumber(name)
					if err == nil {
						value = numValue
					}
				}

				arrayElements = append(arrayElements, value)
			}

		case TokenString, TokenNumber, TokenBoolean:
			// Direct array element
			var value any

			switch token.Type {
			case TokenString:
				value = string(token.Value)
			case TokenNumber:
				strVal := string(token.Value)
				value, _ = parseStringAsNumber(strVal)
			case TokenBoolean:
				value = string(token.Value) == "true"
			}

			arrayElements = append(arrayElements, value)

		case TokenOpenBrace:
			// Nested object in array
			nestedObj, err := p.parseObject()
			if err != nil {
				return nil, err
			}
			arrayElements = append(arrayElements, nestedObj)

		default:
			return nil, p.Error(fmt.Sprintf("unexpected token in object: %v", token.Type))
		}
	}
}