package customfields

import (
	"context"
	"encoding/json"
	"strings"
	"unicode/utf8"

	"production/internal/dbutil"

	"github.com/gofiber/fiber/v2"
	"github.com/google/uuid"
	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgxpool"
)

const maxLabelLen = 255
const maxOptionLen = 255
const maxOptions = 50

type Handler struct {
	db *pgxpool.Pool
}

func NewHandler(db *pgxpool.Pool) *Handler {
	return &Handler{db: db}
}

// Fetch returns field definitions ordered for display. activeOnly=true is
// what order.Create/Update validate against and what the intake form
// renders; activeOnly=false is for the management page, which needs to
// show (and let an owner re-activate) archived fields too.
func Fetch(ctx context.Context, db *pgxpool.Pool, activeOnly bool) ([]FieldDefinition, error) {
	query := `SELECT id, field_key, label, field_type, options, catalog_type_id, required, position, is_active
	          FROM order_field_definitions`
	if activeOnly {
		query += ` WHERE is_active = true`
	}
	query += ` ORDER BY position, created_at`

	rows, err := db.Query(ctx, query)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	out := []FieldDefinition{}
	for rows.Next() {
		var d FieldDefinition
		var optionsRaw []byte
		if err := rows.Scan(&d.ID, &d.FieldKey, &d.Label, &d.FieldType, &optionsRaw, &d.CatalogTypeID, &d.Required, &d.Position, &d.IsActive); err != nil {
			return nil, err
		}
		if len(optionsRaw) > 0 {
			if err := json.Unmarshal(optionsRaw, &d.Options); err != nil {
				return nil, err
			}
		}
		out = append(out, d)
	}
	return out, rows.Err()
}

// ResolveCatalogOptions populates Options on every catalog-linked select
// def from gencatalog's live catalog_entries — order.Create/Update call
// this right after Fetch, before ValidateValues, so ValidateValues itself
// stays a pure, DB-free function (see its own doc comment) while still
// validating against the catalog's current contents, not a stale snapshot.
// One query for every referenced catalog, not one per def.
func ResolveCatalogOptions(ctx context.Context, db *pgxpool.Pool, defs []FieldDefinition) ([]FieldDefinition, error) {
	typeIDs := make([]string, 0)
	seen := make(map[string]bool)
	for _, d := range defs {
		if d.CatalogTypeID != nil && !seen[*d.CatalogTypeID] {
			seen[*d.CatalogTypeID] = true
			typeIDs = append(typeIDs, *d.CatalogTypeID)
		}
	}
	if len(typeIDs) == 0 {
		return defs, nil
	}

	rows, err := db.Query(ctx,
		`SELECT catalog_type_id, name FROM catalog_entries WHERE catalog_type_id = ANY($1::uuid[]) ORDER BY sort_order, name`,
		typeIDs)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	byType := make(map[string][]string)
	for rows.Next() {
		var typeID, name string
		if err := rows.Scan(&typeID, &name); err != nil {
			return nil, err
		}
		byType[typeID] = append(byType[typeID], name)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}

	out := make([]FieldDefinition, len(defs))
	copy(out, defs)
	for i := range out {
		if out[i].CatalogTypeID != nil {
			out[i].Options = byType[*out[i].CatalogTypeID]
		}
	}
	return out, nil
}

// List returns active field definitions with catalog-linked selects'
// Options resolved live — every staff role needs this to render the intake
// form (with real, current dropdown choices), not just the owner who
// manages them.
func (h *Handler) List(c *fiber.Ctx) error {
	defs, err := Fetch(context.Background(), h.db, true)
	if err != nil {
		return c.Status(500).JSON(fiber.Map{"error": "internal error"})
	}
	defs, err = ResolveCatalogOptions(context.Background(), h.db, defs)
	if err != nil {
		return c.Status(500).JSON(fiber.Map{"error": "internal error"})
	}
	return c.JSON(defs)
}

// ListAll includes archived fields — owner-only, for the management page.
func (h *Handler) ListAll(c *fiber.Ctx) error {
	defs, err := Fetch(context.Background(), h.db, false)
	if err != nil {
		return c.Status(500).JSON(fiber.Map{"error": "internal error"})
	}
	return c.JSON(defs)
}

type createInput struct {
	Label         string   `json:"label"`
	FieldType     string   `json:"field_type"`
	Options       []string `json:"options"`
	CatalogTypeID string   `json:"catalog_type_id"`
	Required      bool     `json:"required"`
}

func (body createInput) validate() string {
	if body.Label == "" || utf8.RuneCountInString(body.Label) > maxLabelLen {
		return "label is required and must be under 255 characters"
	}
	if !ValidTypes[body.FieldType] {
		return "field_type must be one of: text, number, select, checkbox"
	}
	if body.CatalogTypeID != "" && body.FieldType != "select" {
		return "catalog_type_id is only valid for select fields"
	}
	// A catalog-linked select needs no static options — ResolveCatalogOptions
	// (see handler's ListEntries-backed lookup) resolves them live from
	// gencatalog at validation time instead.
	if body.FieldType == "select" && body.CatalogTypeID == "" {
		if len(body.Options) == 0 {
			return "select field requires at least one option, or a catalog_type_id"
		}
		if len(body.Options) > maxOptions {
			return "too many options"
		}
		for _, opt := range body.Options {
			if opt == "" || utf8.RuneCountInString(opt) > maxOptionLen {
				return "each option must be non-empty and under 255 characters"
			}
		}
	}
	return ""
}

// Create adds a new field definition. field_key is generated here, never
// derived from the label (see package doc) and never accepted from the
// caller — nothing about it is meant to be human-chosen.
func (h *Handler) Create(c *fiber.Ctx) error {
	var body createInput
	if err := c.BodyParser(&body); err != nil {
		return c.Status(400).JSON(fiber.Map{"error": "invalid request body"})
	}
	if msg := body.validate(); msg != "" {
		return c.Status(400).JSON(fiber.Map{"error": msg})
	}
	// select-only, but stored as-is either way — Update's own validate()
	// enforces the same rule so a later edit can't leave a non-select field
	// with stale options. A catalog-linked field stores no static options at
	// all, even if the caller sent some — they'd never be read.
	options := body.Options
	if body.FieldType != "select" || body.CatalogTypeID != "" {
		options = nil
	}
	optionsJSON, err := json.Marshal(options)
	if err != nil {
		return c.Status(500).JSON(fiber.Map{"error": "internal error"})
	}

	fieldKey := "f_" + strings.ReplaceAll(uuid.New().String(), "-", "")[:12]
	ctx := context.Background()

	var position int
	if err := h.db.QueryRow(ctx, `SELECT COALESCE(MAX(position), -1) + 1 FROM order_field_definitions`).Scan(&position); err != nil {
		return c.Status(500).JSON(fiber.Map{"error": "internal error"})
	}

	var id string
	err = h.db.QueryRow(ctx,
		`INSERT INTO order_field_definitions (field_key, label, field_type, options, catalog_type_id, required, position)
		 VALUES ($1, $2, $3, $4::jsonb, $5::uuid, $6, $7) RETURNING id`,
		fieldKey, body.Label, body.FieldType, optionsJSON, dbutil.NullIfEmpty(body.CatalogTypeID), body.Required, position,
	).Scan(&id)
	if err != nil {
		if dbutil.IsFKViolation(err) {
			return c.Status(404).JSON(fiber.Map{"error": "catalog type not found"})
		}
		return c.Status(500).JSON(fiber.Map{"error": "internal error"})
	}

	var catalogTypeIDPtr *string
	if body.CatalogTypeID != "" {
		catalogTypeIDPtr = &body.CatalogTypeID
	}
	return c.Status(201).JSON(FieldDefinition{
		ID: id, FieldKey: fieldKey, Label: body.Label, FieldType: body.FieldType,
		Options: options, CatalogTypeID: catalogTypeIDPtr, Required: body.Required, Position: position, IsActive: true,
	})
}

type updateInput struct {
	Label         *string   `json:"label"`
	Options       *[]string `json:"options"`
	CatalogTypeID *string   `json:"catalog_type_id"`
	Required      *bool     `json:"required"`
	Position      *int      `json:"position"`
	IsActive      *bool     `json:"is_active"`
}

// Update edits label/options/catalog_type_id/required/position/is_active.
// field_type and field_key are permanently fixed at creation — changing a
// field's type after values of the old type are already stored would make
// those values meaningless (a "select" value with no matching option once
// "text" options disappear, a "text" string once it's a "number"), and the
// key is the only thing tying stored JSONB values back to their
// definition, so it can never move.
//
// catalog_type_id follows the same COALESCE-plus-empty-string-clears
// convention as production/internal/settings.Update: the key omitted
// entirely (Go nil) leaves the link untouched; sent as "" detaches it
// (back to static Options); sent as a UUID re-points it — but only onto a
// field whose field_type is already "select", checked against the stored
// row since createInput/Create is the only place field_type is ever set.
func (h *Handler) Update(c *fiber.Ctx) error {
	id := c.Params("id")
	var body updateInput
	if err := c.BodyParser(&body); err != nil {
		return c.Status(400).JSON(fiber.Map{"error": "invalid request body"})
	}
	if body.Label != nil && (*body.Label == "" || utf8.RuneCountInString(*body.Label) > maxLabelLen) {
		return c.Status(400).JSON(fiber.Map{"error": "label must be non-empty and under 255 characters"})
	}
	if body.Options != nil {
		if len(*body.Options) > maxOptions {
			return c.Status(400).JSON(fiber.Map{"error": "too many options"})
		}
		for _, opt := range *body.Options {
			if opt == "" || utf8.RuneCountInString(opt) > maxOptionLen {
				return c.Status(400).JSON(fiber.Map{"error": "each option must be non-empty and under 255 characters"})
			}
		}
	}

	ctx := context.Background()

	if body.CatalogTypeID != nil && *body.CatalogTypeID != "" {
		var fieldType string
		err := h.db.QueryRow(ctx, `SELECT field_type FROM order_field_definitions WHERE id = $1::uuid`, id).Scan(&fieldType)
		if err == pgx.ErrNoRows {
			return c.Status(404).JSON(fiber.Map{"error": "field not found"})
		}
		if err != nil {
			return c.Status(500).JSON(fiber.Map{"error": "internal error"})
		}
		if fieldType != "select" {
			return c.Status(400).JSON(fiber.Map{"error": "catalog_type_id is only valid for select fields"})
		}
	}

	var optionsJSON []byte
	var err error
	if body.Options != nil {
		optionsJSON, err = json.Marshal(*body.Options)
		if err != nil {
			return c.Status(500).JSON(fiber.Map{"error": "internal error"})
		}
	}

	tag, err := h.db.Exec(ctx,
		`UPDATE order_field_definitions SET
		   label           = COALESCE($1, label),
		   options         = COALESCE($2::jsonb, options),
		   catalog_type_id = CASE WHEN $3::text IS NULL THEN catalog_type_id
		                          WHEN $3::text = '' THEN NULL
		                          ELSE $3::uuid END,
		   required        = COALESCE($4, required),
		   position        = COALESCE($5, position),
		   is_active       = COALESCE($6, is_active)
		 WHERE id = $7::uuid`,
		body.Label, nullIfNil(body.Options, optionsJSON), body.CatalogTypeID, body.Required, body.Position, body.IsActive, id)
	if err != nil {
		if dbutil.IsFKViolation(err) {
			return c.Status(404).JSON(fiber.Map{"error": "catalog type not found"})
		}
		return c.Status(500).JSON(fiber.Map{"error": "internal error"})
	}
	if tag.RowsAffected() == 0 {
		return c.Status(404).JSON(fiber.Map{"error": "field not found"})
	}
	return c.JSON(fiber.Map{"ok": true})
}

// nullIfNil keeps optionsJSON's Postgres NULL (→ COALESCE keeps the
// existing value) when the caller didn't send an options key at all,
// distinct from sending an empty array.
func nullIfNil(options *[]string, marshaled []byte) []byte {
	if options == nil {
		return nil
	}
	return marshaled
}