package main

import (
	"context"
	"errors"
	"net/http"
	"strconv"
	"strings"
	"time"

	"github.com/go-chi/chi/v5"
)

const (
	formStatusDraft     = "draft"
	formStatusPublished = "published"
)

var formPublishingPolicyInstance = formPublishingPolicy{}

type formPublishingPolicy struct{}

var allowedFormFieldTypes = map[string]struct{}{
	"text":     {},
	"textarea": {},
	"email":    {},
	"number":   {},
	"select":   {},
	"checkbox": {},
}

func (a *app) formsAdminMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		claims, _ := r.Context().Value(userClaimsKey).(*accessClaims)
		if claims == nil {
			writeError(w, http.StatusUnauthorized, "no authenticated user")
			return
		}
		if !hasRole(claims, "admin") {
			writeError(w, http.StatusForbidden, "insufficient role for form management")
			return
		}
		next.ServeHTTP(w, r)
	})
}

func (a *app) listForms(w http.ResponseWriter, r *http.Request) {
	a.listCollection("forms", w)
}

func (a *app) createForm(w http.ResponseWriter, r *http.Request) {
	var payload formUpsertRequest
	if err := decodeJSON(r, &payload); err != nil {
		writeError(w, http.StatusBadRequest, "invalid payload")
		return
	}

	doc, err := prepareFormPayload(payload.Doc(), false, nil)
	if err != nil {
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}

	doc, err = a.create("forms", doc)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "failed to create resource")
		return
	}
	writeJSON(w, http.StatusCreated, doc)
}

func (a *app) getForm(w http.ResponseWriter, r *http.Request) {
	a.getCollection("forms", w, r)
}

func (a *app) patchForm(w http.ResponseWriter, r *http.Request) {
	id := chi.URLParam(r, "id")
	var payload formUpsertRequest
	if err := decodeJSON(r, &payload); err != nil {
		writeError(w, http.StatusBadRequest, "invalid patch payload")
		return
	}

	existing, err := a.getByID("forms", id)
	if err != nil {
		if errors.Is(err, ErrNotFound) {
			writeError(w, http.StatusNotFound, "resource not found")
			return
		}
		writeError(w, http.StatusInternalServerError, "failed to load resource")
		return
	}

	patch, err := prepareFormPayload(payload.Doc(), true, existing)
	if err != nil {
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}

	doc, err := a.patch("forms", id, patch)
	if err != nil {
		if errors.Is(err, ErrNotFound) {
			writeError(w, http.StatusNotFound, "resource not found")
			return
		}
		writeError(w, http.StatusInternalServerError, "failed to update resource")
		return
	}

	writeJSON(w, http.StatusOK, doc)
}

func (a *app) deleteForm(w http.ResponseWriter, r *http.Request) {
	a.deleteCollection("forms", w, r)
}

func (a *app) listFormSubmissions(w http.ResponseWriter, r *http.Request) {
	if a.db == nil {
		writeError(w, http.StatusServiceUnavailable, "database not configured")
		return
	}

	formID := strings.TrimSpace(chi.URLParam(r, "id"))
	if formID == "" {
		writeError(w, http.StatusBadRequest, "form id is required")
		return
	}

	docs, err := a.list("form_submissions", Doc{"formId": formID}, Sort{{Key: "submittedAt", Value: -1}, {Key: "updatedAt", Value: -1}})
	if err != nil {
		writeError(w, http.StatusInternalServerError, "failed to list form submissions")
		return
	}

	writeJSON(w, http.StatusOK, docs)
}

func (a *app) getPublicForm(w http.ResponseWriter, r *http.Request) {
	if a.db == nil {
		writeError(w, http.StatusServiceUnavailable, "database not configured")
		return
	}

	formID := strings.TrimSpace(chi.URLParam(r, "id"))
	if formID == "" {
		writeError(w, http.StatusBadRequest, "form id is required")
		return
	}

	ctx, cancel := context.WithTimeout(r.Context(), 8*time.Second)
	defer cancel()

	var form Doc
	if err := a.db.Collection("forms").FindOne(ctx, Doc{"id": formID}).Decode(&form); err != nil {
		if errors.Is(err, ErrNotFound) {
			writeError(w, http.StatusNotFound, "form not found")
			return
		}
		writeError(w, http.StatusInternalServerError, "failed to load form")
		return
	}
	normalizeDocument(form)

	status, _ := asString(form["status"])
	if status != formStatusPublished {
		writeError(w, http.StatusNotFound, "form not found")
		return
	}

	schema, _, err := normalizeFormSchema(form["schema"])
	if err != nil {
		writeError(w, http.StatusInternalServerError, "form schema is invalid")
		return
	}

	writeJSON(w, http.StatusOK, publicFormResponse{
		ID:          stringValue(form["id"]),
		Name:        stringValue(form["name"]),
		Description: stringValue(form["description"]),
		Schema:      schema,
	})
}

func (a *app) createPublicFormSubmission(w http.ResponseWriter, r *http.Request) {
	if a.db == nil {
		writeError(w, http.StatusServiceUnavailable, "database not configured")
		return
	}

	formID := strings.TrimSpace(chi.URLParam(r, "id"))
	if formID == "" {
		writeError(w, http.StatusBadRequest, "form id is required")
		return
	}

	ctx, cancel := context.WithTimeout(r.Context(), 8*time.Second)
	defer cancel()

	var form Doc
	if err := a.db.Collection("forms").FindOne(ctx, Doc{"id": formID}).Decode(&form); err != nil {
		if errors.Is(err, ErrNotFound) {
			writeError(w, http.StatusNotFound, "form not found")
			return
		}
		writeError(w, http.StatusInternalServerError, "failed to load form")
		return
	}
	normalizeDocument(form)

	status, _ := asString(form["status"])
	if status != formStatusPublished {
		writeError(w, http.StatusNotFound, "form not found")
		return
	}

	schema, _, err := normalizeFormSchema(form["schema"])
	if err != nil {
		writeError(w, http.StatusInternalServerError, "form schema is invalid")
		return
	}

	var payload struct {
		Values map[string]any `json:"values"`
	}
	if err := decodeJSON(r, &payload); err != nil {
		writeError(w, http.StatusBadRequest, "invalid payload")
		return
	}
	if payload.Values == nil {
		payload.Values = map[string]any{}
	}

	normalizedValues, err := validateFormSubmission(schema, payload.Values)
	if err != nil {
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}

	submission := Doc{
		"formId":      formID,
		"values":      normalizedValues,
		"submittedAt": time.Now().UnixMilli(),
	}
	submission, err = a.create("form_submissions", submission)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "failed to store form submission")
		return
	}

	submittedAt := int64(0)
	switch value := submission["submittedAt"].(type) {
	case int64:
		submittedAt = value
	case int32:
		submittedAt = int64(value)
	case int:
		submittedAt = int64(value)
	case float64:
		submittedAt = int64(value)
	}
	writeJSON(w, http.StatusCreated, publicFormSubmissionCreateResponse{
		ID:          stringValue(submission["id"]),
		FormID:      stringValue(submission["formId"]),
		SubmittedAt: submittedAt,
	})
}

func prepareFormPayload(payload Doc, partial bool, existing Doc) (Doc, error) {
	if payload == nil {
		payload = Doc{}
	}

	name, hasName, err := getOptionalString(payload, "name")
	if err != nil {
		return nil, errors.New("name must be a string")
	}
	if !partial && (!hasName || name == "") {
		return nil, errors.New("name is required")
	}
	if hasName {
		payload["name"] = name
	}

	if err := applyPublishingPolicy(payload, partial, existing, formPublishingPolicyInstance); err != nil {
		return nil, err
	}

	description, hasDescription, err := getOptionalString(payload, "description")
	if err != nil {
		return nil, errors.New("description must be a string")
	}
	if hasDescription {
		payload["description"] = description
	}

	schema, hasSchema, err := normalizeFormSchema(payload["schema"])
	if err != nil {
		return nil, err
	}
	if hasSchema {
		payload["schema"] = schema
	}

	return payload, nil
}

func (formPublishingPolicy) defaultStatus() string {
	return formStatusDraft
}

func (formPublishingPolicy) isAllowedStatus(status string) bool {
	return status == formStatusDraft || status == formStatusPublished
}

func (formPublishingPolicy) invalidStatusMessage() string {
	return "status must be one of: draft, published"
}

func (formPublishingPolicy) validate(payload Doc, existing Doc) error {
	status, ok := mergedPublishingString(payload, existing, "status")
	if !ok || status != formStatusPublished {
		return nil
	}

	schemaValues, has := mergedPublishingValue(payload, existing, "schema")
	if !has {
		return errors.New("schema is required when status is published")
	}

	normalized, _, err := normalizeFormSchema(schemaValues)
	if err != nil {
		return err
	}
	if len(normalized) == 0 {
		return errors.New("schema is required when status is published")
	}

	return nil
}

func normalizeFormSchema(raw any) ([]Doc, bool, error) {
	if raw == nil {
		return nil, false, nil
	}

	var values []any
	switch source := raw.(type) {
	case []any:
		values = source
	case List:
		values = []any(source)
	case []Doc:
		values = make([]any, 0, len(source))
		for _, field := range source {
			values = append(values, field)
		}
	case []map[string]any:
		values = make([]any, 0, len(source))
		for _, field := range source {
			values = append(values, field)
		}
	default:
		return nil, false, errors.New("schema must be an array")
	}

	normalized := make([]Doc, 0, len(values))
	for _, item := range values {
		fieldMap, ok := item.(map[string]any)
		if !ok {
			bsonField, docOK := item.(Doc)
			if !docOK {
				return nil, false, errors.New("schema fields must be objects")
			}
			fieldMap = map[string]any(bsonField)
		}

		nameRaw, ok := fieldMap["name"]
		if !ok {
			return nil, false, errors.New("schema field name is required")
		}
		name, ok := nameRaw.(string)
		if !ok || strings.TrimSpace(name) == "" {
			return nil, false, errors.New("schema field name must be a string")
		}
		name = strings.TrimSpace(name)

		typeRaw, ok := fieldMap["type"]
		if !ok {
			return nil, false, errors.New("schema field type is required")
		}
		fieldType, ok := typeRaw.(string)
		if !ok {
			return nil, false, errors.New("schema field type must be a string")
		}
		fieldType = strings.ToLower(strings.TrimSpace(fieldType))
		if _, valid := allowedFormFieldTypes[fieldType]; !valid {
			return nil, false, errors.New("schema field type is invalid")
		}

		normalizedField := Doc{
			"name": name,
			"type": fieldType,
		}

		if labelRaw, has := fieldMap["label"]; has {
			label, ok := labelRaw.(string)
			if !ok {
				return nil, false, errors.New("schema field label must be a string")
			}
			normalizedField["label"] = strings.TrimSpace(label)
		}

		if requiredRaw, has := fieldMap["required"]; has {
			required, ok := requiredRaw.(bool)
			if !ok {
				return nil, false, errors.New("schema field required must be a boolean")
			}
			normalizedField["required"] = required
		} else {
			normalizedField["required"] = false
		}

		if optionsRaw, has := fieldMap["options"]; has {
			options, _, err := normalizeStringSlice(optionsRaw)
			if err != nil {
				return nil, false, errors.New("schema field options must be an array of strings")
			}
			normalizedField["options"] = options
		}

		normalized = append(normalized, normalizedField)
	}

	return normalized, true, nil
}

func validateFormSubmission(schema []Doc, values map[string]any) (Doc, error) {
	schemaByName := map[string]Doc{}
	for _, field := range schema {
		name, _ := field["name"].(string)
		schemaByName[name] = field
	}

	normalized := Doc{}
	for key, value := range values {
		field, exists := schemaByName[key]
		if !exists {
			return nil, errors.New("unknown field: " + key)
		}

		fieldType, _ := field["type"].(string)
		normalizedValue, err := normalizeSubmissionValue(fieldType, value)
		if err != nil {
			return nil, errors.New(key + ": " + err.Error())
		}
		if fieldType == "select" {
			if err := validateSelectSubmissionOption(field, normalizedValue); err != nil {
				return nil, errors.New(key + ": " + err.Error())
			}
		}
		normalized[key] = normalizedValue
	}

	for _, field := range schema {
		name, _ := field["name"].(string)
		required, _ := field["required"].(bool)
		if !required {
			continue
		}

		value, exists := normalized[name]
		if !exists || isEmptySubmissionValue(value) {
			return nil, errors.New("missing required field: " + name)
		}
	}

	return normalized, nil
}

func validateSelectSubmissionOption(field Doc, value any) error {
	selected, ok := value.(string)
	if !ok {
		return errors.New("must be a string")
	}

	optionsRaw, hasOptions := field["options"]
	if !hasOptions || optionsRaw == nil {
		return nil
	}

	options, hasNormalizedOptions, err := normalizeStringSlice(optionsRaw)
	if err != nil {
		return errors.New("select options are invalid")
	}
	if !hasNormalizedOptions {
		return nil
	}

	normalizedSelected := strings.ToLower(strings.TrimSpace(selected))
	for _, option := range options {
		if strings.ToLower(strings.TrimSpace(option)) == normalizedSelected {
			return nil
		}
	}

	return errors.New("must be one of the configured options")
}

func normalizeSubmissionValue(fieldType string, value any) (any, error) {
	switch fieldType {
	case "text", "textarea", "email", "select":
		text, ok := value.(string)
		if !ok {
			return nil, errors.New("must be a string")
		}
		trimmed := strings.TrimSpace(text)
		if fieldType == "email" && trimmed != "" && !strings.Contains(trimmed, "@") {
			return nil, errors.New("must be a valid email")
		}
		return trimmed, nil
	case "number":
		switch typed := value.(type) {
		case float64:
			return typed, nil
		case float32:
			return float64(typed), nil
		case int:
			return float64(typed), nil
		case int64:
			return float64(typed), nil
		case string:
			if strings.TrimSpace(typed) == "" {
				return "", nil
			}
			parsed, err := strconv.ParseFloat(strings.TrimSpace(typed), 64)
			if err != nil {
				return nil, errors.New("must be a number")
			}
			return parsed, nil
		default:
			return nil, errors.New("must be a number")
		}
	case "checkbox":
		boolean, ok := value.(bool)
		if !ok {
			return nil, errors.New("must be a boolean")
		}
		return boolean, nil
	default:
		return nil, errors.New("unsupported field type")
	}
}

func isEmptySubmissionValue(value any) bool {
	switch typed := value.(type) {
	case string:
		return strings.TrimSpace(typed) == ""
	default:
		return value == nil
	}
}