package httputil

import (
	"context"
	"encoding/json"
	"net/http"

	"code.nochebuena.dev/einherjar/contracts/logging"
	"code.nochebuena.dev/einherjar/core/valid"
	"code.nochebuena.dev/einherjar/core/xerrors"
)

// Handle adapts a typed business function to http.HandlerFunc.
//   - Decodes the JSON request body into Req.
//   - Validates Req using the provided [valid.Validator].
//   - Calls fn with the request context and decoded Req.
//   - Encodes Res as JSON with HTTP 200 on success.
//   - On error: logs via [Error] (level derived from HTTP status) and writes the standardized JSON body.
func Handle[Req, Res any](v valid.Validator, logger logging.Logger, fn func(ctx context.Context, req Req) (Res, error)) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		var req Req
		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
			Error(logger, w, r, xerrors.New(xerrors.ErrInvalidInput, "invalid JSON: "+err.Error()))
			return
		}
		if err := v.Struct(req); err != nil {
			Error(logger, w, r, err)
			return
		}
		res, err := fn(r.Context(), req)
		if err != nil {
			Error(logger, w, r, err)
			return
		}
		JSON(w, http.StatusOK, res)
	}
}

// HandleNoBody adapts a typed function with no request body (GET, HEAD).
// Calls fn with the request context; encodes the result as JSON with HTTP 200.
// On error: logs via [Error] and writes the standardized JSON body.
func HandleNoBody[Res any](logger logging.Logger, fn func(ctx context.Context) (Res, error)) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		res, err := fn(r.Context())
		if err != nil {
			Error(logger, w, r, err)
			return
		}
		JSON(w, http.StatusOK, res)
	}
}

// HandleEmpty adapts a typed function with a request body but no response body.
// Decodes and validates Req, calls fn, returns 204 No Content on success.
// On error: logs via [Error] and writes the standardized JSON body.
func HandleEmpty[Req any](v valid.Validator, logger logging.Logger, fn func(ctx context.Context, req Req) error) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		var req Req
		if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
			Error(logger, w, r, xerrors.New(xerrors.ErrInvalidInput, "invalid JSON: "+err.Error()))
			return
		}
		if err := v.Struct(req); err != nil {
			Error(logger, w, r, err)
			return
		}
		if err := fn(r.Context(), req); err != nil {
			Error(logger, w, r, err)
			return
		}
		NoContent(w)
	}
}