package configkit

import (
	"math"
	"reflect"
	"slices"
	"strconv"

	"gitea.maximumdirect.net/eric/ConfigKit/internal/document"
)

type overrideValueBuilder struct {
	sourceID string
	active   map[valueVisit]bool
	bytes    int64
	nodes    int
}

func (b *overrideValueBuilder) build(value any, path Path, depth int) (*document.Node, *Diagnostic) {
	if depth > maxDocumentDepth {
		return nil, overrideValueDiagnostic(CodeOverrideLimitExceeded, path, "configuration override exceeds the depth limit")
	}
	b.nodes++
	if b.nodes > maxDocumentNodes {
		return nil, overrideValueDiagnostic(CodeOverrideLimitExceeded, path, "configuration override exceeds the node limit")
	}
	location := document.Location{SourceID: b.sourceID}
	switch value := value.(type) {
	case nil:
		return &document.Node{Kind: document.Null, Location: location}, nil
	case string:
		if !b.addBytes(len(value)) {
			return nil, overrideValueDiagnostic(CodeOverrideLimitExceeded, path, "configuration override exceeds the record string-byte limit")
		}
		return &document.Node{Kind: document.String, Text: value, Location: location}, nil
	case bool:
		return &document.Node{Kind: document.Boolean, Text: strconv.FormatBool(value), Location: location}, nil
	case int:
		return overrideNumber(strconv.FormatInt(int64(value), 10), location), nil
	case int8:
		return overrideNumber(strconv.FormatInt(int64(value), 10), location), nil
	case int16:
		return overrideNumber(strconv.FormatInt(int64(value), 10), location), nil
	case int32:
		return overrideNumber(strconv.FormatInt(int64(value), 10), location), nil
	case int64:
		return overrideNumber(strconv.FormatInt(value, 10), location), nil
	case uint:
		return overrideNumber(strconv.FormatUint(uint64(value), 10), location), nil
	case uint8:
		return overrideNumber(strconv.FormatUint(uint64(value), 10), location), nil
	case uint16:
		return overrideNumber(strconv.FormatUint(uint64(value), 10), location), nil
	case uint32:
		return overrideNumber(strconv.FormatUint(uint64(value), 10), location), nil
	case uint64:
		return overrideNumber(strconv.FormatUint(value, 10), location), nil
	case float32:
		if math.IsNaN(float64(value)) || math.IsInf(float64(value), 0) {
			return nil, overrideValueDiagnostic(CodeOverrideInvalidValue, path, "configuration override float must be finite")
		}
		return overrideNumber(strconv.FormatFloat(float64(value), 'g', -1, 32), location), nil
	case float64:
		if math.IsNaN(value) || math.IsInf(value, 0) {
			return nil, overrideValueDiagnostic(CodeOverrideInvalidValue, path, "configuration override float must be finite")
		}
		return overrideNumber(strconv.FormatFloat(value, 'g', -1, 64), location), nil
	case []any:
		if value == nil {
			return &document.Node{Kind: document.Null, Location: location}, nil
		}
		leave, diagnostic := b.enter(reflect.ValueOf(value), path)
		if diagnostic != nil {
			return nil, diagnostic
		}
		defer leave()
		if len(value) > maxDocumentNodes-b.nodes {
			return nil, overrideValueDiagnostic(CodeOverrideLimitExceeded, path, "configuration override exceeds the node limit")
		}
		node := &document.Node{Kind: document.Sequence, Location: location, Sequence: make([]*document.Node, len(value))}
		for index, child := range value {
			built, diagnostic := b.build(child, path.Index(index), depth+1)
			if diagnostic != nil {
				return nil, diagnostic
			}
			node.Sequence[index] = built
		}
		return node, nil
	case map[string]any:
		if value == nil {
			return &document.Node{Kind: document.Null, Location: location}, nil
		}
		leave, diagnostic := b.enter(reflect.ValueOf(value), path)
		if diagnostic != nil {
			return nil, diagnostic
		}
		defer leave()
		if len(value) > (maxDocumentNodes-b.nodes)/2 {
			return nil, overrideValueDiagnostic(CodeOverrideLimitExceeded, path, "configuration override exceeds the node limit")
		}
		keys := make([]string, 0, len(value))
		for key := range value {
			keys = append(keys, key)
		}
		slices.Sort(keys)
		node := &document.Node{Kind: document.Mapping, Location: location, Mapping: make([]document.Entry, 0, len(keys))}
		for _, key := range keys {
			b.nodes++ // mapping key
			if !b.addBytes(len(key)) {
				return nil, overrideValueDiagnostic(CodeOverrideLimitExceeded, path.Key(key), "configuration override exceeds the record string-byte limit")
			}
			built, diagnostic := b.build(value[key], path.Key(key), depth+1)
			if diagnostic != nil {
				return nil, diagnostic
			}
			node.Mapping = append(node.Mapping, document.Entry{Key: key, KeyLocation: location, ValueLocation: location, Value: built})
		}
		return node, nil
	default:
		return nil, overrideValueDiagnostic(CodeOverrideInvalidValue, path, "configuration override value has an unsupported type")
	}
}

func (b *overrideValueBuilder) addBytes(count int) bool {
	if count < 0 || int64(count) > maxSourceBytes-b.bytes {
		return false
	}
	b.bytes += int64(count)
	return true
}

func (b *overrideValueBuilder) enter(value reflect.Value, path Path) (func(), *Diagnostic) {
	visit, ok := visitFor(value)
	if !ok {
		return func() {}, nil
	}
	if b.active[visit] {
		return nil, overrideValueDiagnostic(CodeOverrideInvalidValue, path, "configuration override values must not contain cycles")
	}
	b.active[visit] = true
	return func() { delete(b.active, visit) }, nil
}

func overrideValueDiagnostic(code Code, path Path, message string) *Diagnostic {
	return &Diagnostic{Code: code, Severity: SeverityError, Path: path.clone(), Message: message}
}

func overrideNumber(text string, location document.Location) *document.Node {
	return &document.Node{Kind: document.Number, Text: text, Location: location}
}