package cabana

import (
	"bytes"
	"errors"
	"fmt"
	"io/fs"
	"regexp"
	"slices"
	"strings"

	"git.golem15.com/golem15/summercms/modules/pact"
	"github.com/goccy/go-yaml"
	"github.com/goccy/go-yaml/ast"
)

// relationFormRefusedTypes are the field types a relation form (manage.form,
// view.form, pivot.form) may not use (D-23): pickers, nested managers and
// plugin extensions need a parent record scope a child modal does not have.
var relationFormRefusedTypes = map[string]bool{
	"relation": true, "relation-manager": true, "widget": true, "partial": true,
}

// pivotFieldPattern is WinterCMS's pivot form field name, pivot[column].
var pivotFieldPattern = regexp.MustCompile(`^pivot\[([A-Za-z_][A-Za-z0-9_]*)\]$`)

// pivotFieldName normalizes pivot[x] to x; any other name is unchanged.
func pivotFieldName(name string) string {
	if m := pivotFieldPattern.FindStringSubmatch(name); m != nil {
		return m[1]
	}
	return name
}

// relationModelController stands in for an admin controller around a
// relation form's model (the related model, or the pivot model), so the
// controller form pipeline (writable fields, file and date fields, fill,
// validate, projection) runs against that model. Its ID is the owning
// controller's, so boot errors and lifecycle failures name it.
type relationModelController struct {
	id        string
	newRecord func() any
}

func (c relationModelController) ID() string        { return c.id }
func (c relationModelController) ModelName() string { return "" }
func (c relationModelController) ConfigDir() string { return "" }
func (c relationModelController) NewRecord() any    { return c.newRecord() }

// compileRelationForms compiles a relation's forms (D-11, D-14, D-23): the
// manage form (manage.form, else the top-level form) used to create and
// update children, the view form (view.form, else the top-level form) used
// to preview them, and the pivot form (pivot.form, belongsToMany only). It
// also enforces the toolbar rules that depend on them: create and update
// need a manage form, and unlink on a hasMany needs a nullable ForeignKey.
func compileRelationForms(pluginID string, ctl pact.AdminController, fsys fs.FS, file string, doc relationDocument, cr *CompiledRelation) error {
	name := cr.Contract.Name
	fail := func(err error) error {
		return bootErr(pluginID, ctl.ID(), file, fmt.Errorf("relation %s: %w", name, err))
	}
	buttons := cr.Schema.View.ToolbarButtons
	writes := slices.Contains(buttons, "create") || slices.Contains(buttons, "update")
	manageRef := strings.TrimSpace(doc.Manage.Form)
	if manageRef == "" {
		manageRef = strings.TrimSpace(doc.Form)
	}
	viewRef := strings.TrimSpace(doc.View.Form)
	if viewRef == "" {
		viewRef = strings.TrimSpace(doc.Form)
	}
	if writes && manageRef == "" {
		return fail(errors.New("toolbar buttons create and update need manage.form (or a top-level form)"))
	}
	if cr.hasMany() && slices.Contains(buttons, "unlink") && !cr.deferrable {
		return fail(fmt.Errorf("unlink needs a nullable ForeignKey %s (a pointer field)", cr.Contract.ForeignKey))
	}
	cr.Schema.relatedModel = cr.Contract.NewRelated
	if manageRef != "" {
		child, err := compileRelationForm(pluginID, ctl, fsys, file, manageRef, cr, "manage", writes)
		if err != nil {
			return err
		}
		cr.child = child
		cr.Schema.manageForm = child.Form
		cr.Schema.ManageForm = child.Form.Fields
	}
	if viewRef != "" {
		view := cr.child
		if viewRef != manageRef || view == nil {
			compiled, err := compileRelationForm(pluginID, ctl, fsys, file, viewRef, cr, "view", false)
			if err != nil {
				return err
			}
			view = compiled
		}
		cr.view = view
		cr.Schema.viewForm = view.Form
		cr.Schema.ViewForm = view.Form.Fields
	}
	if doc.Pivot != nil {
		ref := strings.TrimSpace(doc.Pivot.Form)
		if ref == "" {
			return fail(errors.New("pivot needs a form"))
		}
		if cr.hasMany() {
			return fail(errors.New("pivot.form is only valid on a belongsToMany relation"))
		}
		pivot, err := compileRelationForm(pluginID, ctl, fsys, file, ref, cr, "pivot", false)
		if err != nil {
			return err
		}
		cr.pivot = pivot
		cr.Schema.pivotForm = pivot.Form
		cr.Schema.PivotForm = pivot.Form.Fields
		cr.Schema.pivotModel = cr.Contract.NewPivot
	}
	return nil
}

// compileRelationForm reads one relation form file and binds it to its
// model: the related model for the manage and view forms, the pivot model
// for the pivot form. writable additionally requires the model to implement
// lagoon.HasFillable and Rules (create and update fill and validate it).
func compileRelationForm(pluginID string, ctl pact.AdminController, fsys fs.FS, cfgFile, ref string, cr *CompiledRelation, purpose string, writable bool) (*CompiledController, error) {
	relation := cr.Contract.Name
	path, err := assetPath(pluginID, ref)
	if err != nil {
		return nil, bootErr(pluginID, ctl.ID(), cfgFile, fmt.Errorf("relation %s %s form: %w", relation, purpose, err))
	}
	fail := func(err error) error {
		return bootErr(pluginID, ctl.ID(), path, fmt.Errorf("relation %s %s form: %w", relation, purpose, err))
	}
	raw, err := readAsset(fsys, path)
	if err != nil {
		return nil, fail(err)
	}
	var fields []FormField
	if purpose == "pivot" {
		fields, err = decodePivotFields(raw)
	} else {
		fields, err = decodeFields(raw)
	}
	if err != nil {
		return nil, fail(err)
	}
	newModel := cr.Contract.NewRelated
	if purpose == "pivot" {
		newModel = cr.Contract.NewPivot
	}
	model := newModel()
	for _, field := range fields {
		if relationFormRefusedTypes[field.Type] {
			return nil, fail(fmt.Errorf("field %s: type %s is not supported in a relation form (%s)", field.Name, field.Type, purpose))
		}
		if cr.hasMany() && field.Name == cr.Contract.ForeignKey {
			return nil, fail(fmt.Errorf("field %s is the relation's ForeignKey; the server sets it", field.Name))
		}
		if purpose == "pivot" {
			if !scalarFormField(field.Type) {
				return nil, fail(fmt.Errorf("field %s: type %s is not supported in a pivot form", field.Name, field.Type))
			}
			if protectedPivotColumn(field.Name, cr.Contract) || slices.Contains(cr.Contract.HookPivotColumns, field.Name) {
				return nil, fail(fmt.Errorf("field %s is a server-owned pivot column", field.Name))
			}
		}
		if field.optionsMethod != "" && modelDropdownProvider(model) == nil {
			return nil, fail(fmt.Errorf("dropdown method %s requires DropdownOptions on the %s model", field.optionsMethod, purpose))
		}
	}
	cc := &CompiledController{
		PluginID:   pluginID,
		Controller: relationModelController{id: ctl.ID(), newRecord: newModel},
		Form:       &FormSchema{Fields: fields, fieldsPath: path},
	}
	if err := BindWritableFields(cc); err != nil {
		return nil, fail(errors.New(strings.TrimPrefix(err.Error(), "cabana: controller "+ctl.ID()+": ")))
	}
	if writable {
		if _, err := newWritableModel(cc); err != nil {
			return nil, fail(errors.New("the related model must implement lagoon.HasFillable and Rules"))
		}
	}
	if purpose == "pivot" {
		if err := checkFormDates(pluginID, cc); err != nil {
			return nil, err
		}
		return cc, nil
	}
	if err := compileFileFields(pluginID, cc); err != nil {
		return nil, err
	}
	if writable {
		if err := compileDateFields(pluginID, cc); err != nil {
			return nil, err
		}
		return cc, nil
	}
	if err := checkFormDates(pluginID, cc); err != nil {
		return nil, err
	}
	return cc, nil
}

// checkFormDates runs the D-19 Go type check of every datepicker field and
// records them, without requiring a fillable model (read-only and pivot
// forms).
func checkFormDates(pluginID string, cc *CompiledController) error {
	model := cc.Controller.(pact.AdminRecordSource).NewRecord()
	for _, field := range cc.Form.Fields {
		if field.Type != "datepicker" {
			continue
		}
		if err := checkDateType(model, field); err != nil {
			return bootErr(pluginID, controllerID(cc), cc.Form.fieldsPath, err)
		}
		if cc.dates == nil {
			cc.dates = map[string]*compiledDate{}
		}
		cc.dates[field.Name] = &compiledDate{
			name: field.Name, mode: field.Mode,
			min: field.MinDate, max: field.MaxDate,
			ignoreTimezone: field.IgnoreTimezone,
		}
	}
	return nil
}

// pivotFieldsFile is a pivot form's fields.yaml: WinterCMS names its fields
// pivot[column], which compile to the bare column name.
type pivotFieldsFile struct {
	Fields pivotFieldMap `yaml:"fields"`
}

type pivotFieldMap struct {
	items []FormField
}

func (m *pivotFieldMap) UnmarshalYAML(node ast.Node) error {
	items, err := decodeFieldMapping(node, pivotFieldName)
	if err != nil {
		return err
	}
	m.items = items
	return nil
}

func decodePivotFields(raw []byte) ([]FormField, error) {
	dec := yaml.NewDecoder(bytes.NewReader(raw), yaml.DisallowUnknownField())
	var doc pivotFieldsFile
	if err := dec.Decode(&doc); err != nil {
		return nil, normalizeYAMLError(err)
	}
	if doc.Fields.items == nil {
		return []FormField{}, nil
	}
	return doc.Fields.items, nil
}

// modelDropdownProvider is model as a pact.DropdownOptionsProvider, or nil.
func modelDropdownProvider(model any) pact.DropdownOptionsProvider {
	if p, ok := model.(pact.DropdownOptionsProvider); ok && p != nil {
		return p
	}
	return nil
}