package commandkit

import (
	"encoding/json"
	"fmt"
	"io"
	"strconv"
	"strings"
)

// ParseCLIJSON parses exactly one JSON value for use in CLI inputs. Integer
// tokens become int64, or uint64 for larger nonnegative integers; decimal and
// exponent tokens become float64. Nested values follow the same rules. Syntax
// errors and numbers outside the selected Go types' ranges are returned.
func ParseCLIJSON(input string) (any, error) {
	decoder := json.NewDecoder(strings.NewReader(input))
	decoder.UseNumber()
	var value any
	if err := decoder.Decode(&value); err != nil {
		return nil, err
	}
	var extra any
	if err := decoder.Decode(&extra); err != io.EOF {
		if err != nil {
			return nil, err
		}
		return nil, fmt.Errorf("unexpected additional JSON value")
	}
	return convertCLIJSON(value)
}

// CLI inputs use ordinary Go numbers for upstream consumers. Classification
// follows the token's syntax, so 1.0 and 1e0 remain float64. Unlike report
// serialization, this boundary deliberately accepts float64 approximation.
func convertCLIJSON(value any) (any, error) {
	switch v := value.(type) {
	case json.Number:
		token := string(v)
		if strings.ContainsAny(token, ".eE") {
			result, err := strconv.ParseFloat(token, 64)
			if err != nil {
				return nil, fmt.Errorf("JSON number %q: %w", token, err)
			}
			return result, nil
		}
		result, err := strconv.ParseInt(token, 10, 64)
		if err == nil {
			return result, nil
		}
		if !strings.HasPrefix(token, "-") {
			unsigned, unsignedErr := strconv.ParseUint(token, 10, 64)
			if unsignedErr == nil {
				return unsigned, nil
			}
			return nil, fmt.Errorf("JSON integer %q: %w", token, unsignedErr)
		}
		return nil, fmt.Errorf("JSON integer %q: %w", token, err)
	case []any:
		for index, item := range v {
			converted, err := convertCLIJSON(item)
			if err != nil {
				return nil, err
			}
			v[index] = converted
		}
	case map[string]any:
		for key, item := range v {
			converted, err := convertCLIJSON(item)
			if err != nil {
				return nil, err
			}
			v[key] = converted
		}
	}
	return value, nil
}