package config

import (
	"encoding"
	"errors"
	"math"
	"reflect"
	"strconv"
	"strings"
	"time"
)

// LoadProject clones defaults, resolves only explicit file references, binds the
// provided fields and validates. Empty path uses only defaults. No env tags,
// prefixes, aliases or implicit environment overlays are applied.
func LoadProject[T any](path string, defaults T, loaders ...*Loader) (T, error) {
	var zero T
	loader, err := selectLoader(loaders)
	if err != nil {
		return zero, err
	}
	if err = rejectEnvironmentTags(reflect.TypeOf(defaults), map[reflect.Type]bool{}); err != nil {
		return zero, err
	}
	doc := Document{Value: map[string]any{}}
	if path != "" {
		doc, err = loader.read(path)
		if err != nil {
			return zero, err
		}
	}
	cfg, err := bindDocument(doc, defaults)
	if err != nil {
		return zero, locateError(err, path, doc)
	}
	if valid, ok := any(&cfg).(interface{ Validate() error }); ok {
		if err = valid.Validate(); err != nil {
			return zero, locateError(err, path, doc)
		}
	} else if valid, ok := any(cfg).(interface{ Validate() error }); ok {
		if err = valid.Validate(); err != nil {
			return zero, locateError(err, path, doc)
		}
	}
	return cfg, nil
}
func locateError(err error, path string, doc Document) *Error {
	d := validationError(err)
	d.File = path
	if d.Line == 0 {
		p := doc.Positions[d.Field]
		d.Line = p.Line
		d.Column = p.Column
	}
	for field := d.Field; field != ""; {
		if names := doc.environments[field]; len(names) > 0 {
			d.Env = strings.Join(names, ", ")
			break
		}
		i := strings.LastIndexAny(field, ".[")
		if i < 0 {
			break
		}
		field = field[:i]
	}
	return d
}

// Reject removed declarations rather than silently ignoring deployment rules.
func rejectEnvironmentTags(t reflect.Type, seen map[reflect.Type]bool) error {
	if t == nil || seen[t] {
		return nil
	}
	seen[t] = true
	switch t.Kind() {
	case reflect.Pointer, reflect.Slice, reflect.Array, reflect.Map:
		return rejectEnvironmentTags(t.Elem(), seen)
	case reflect.Struct:
		for i := 0; i < t.NumField(); i++ {
			f := t.Field(i)
			if f.PkgPath != "" {
				continue
			}
			_, env := f.Tag.Lookup("env")
			_, def := f.Tag.Lookup("envDefault")
			if env || def {
				return &Error{Field: f.Name, Reason: "env/envDefault tags were removed; use Default() and explicit file references; see CONFIG.md"}
			}
			if f.Tag.Get("json") != "-" {
				if err := rejectEnvironmentTags(f.Type, seen); err != nil {
					return err
				}
			}
		}
	}
	return nil
}

var textType = reflect.TypeOf((*encoding.TextUnmarshaler)(nil)).Elem()
var durationType = reflect.TypeOf(time.Duration(0))

func parseTextValue(v reflect.Value, raw string) (err error) {
	defer func() {
		if recover() != nil {
			err = errors.New("invalid custom value")
		}
	}()
	if v.Kind() == reflect.Pointer {
		v.Set(reflect.New(v.Type().Elem()))
		return parseTextValue(v.Elem(), raw)
	}
	if v.CanAddr() && v.Addr().Type().Implements(textType) {
		return v.Addr().Interface().(encoding.TextUnmarshaler).UnmarshalText([]byte(raw))
	}
	if v.Type() == durationType {
		d, err := time.ParseDuration(raw)
		if err == nil {
			v.SetInt(int64(d))
		}
		return err
	}
	switch v.Kind() {
	case reflect.String:
		v.SetString(raw)
		return nil
	case reflect.Bool:
		x, err := strconv.ParseBool(raw)
		if err == nil {
			v.SetBool(x)
		}
		return err
	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
		x, err := strconv.ParseInt(raw, 10, v.Type().Bits())
		if err == nil {
			v.SetInt(x)
		}
		return err
	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
		x, err := strconv.ParseUint(raw, 10, v.Type().Bits())
		if err == nil {
			v.SetUint(x)
		}
		return err
	case reflect.Float32, reflect.Float64:
		x, err := strconv.ParseFloat(raw, v.Type().Bits())
		if err == nil && (math.IsNaN(x) || math.IsInf(x, 0)) {
			return errors.New("nonfinite value")
		}
		if err == nil {
			v.SetFloat(x)
		}
		return err
	}
	return errors.New("expected scalar text")
}