// Package ops holds the list operations shared by the CLI and the MCP server.
//
// Both surfaces expose the same three modes; keeping the fetch loop here is
// what keeps them congruent instead of drifting apart.
package ops

import (
	"context"
	"errors"
	"fmt"

	"gogs.netdome.biz/paul/cheapo/internal/game"
)

// Mode selects what List returns.
type Mode string

const (
	// Free returns games that are free right now.
	Free Mode = "free"
	// Upcoming returns announced future giveaways (stores with that capability only).
	Upcoming Mode = "upcoming"
	// Deals returns discounted games (stores with that capability only).
	Deals Mode = "deals"
)

// Modes lists the accepted Mode values in a stable order.
var Modes = []Mode{Free, Upcoming, Deals}

// ParseMode maps a mode name to a Mode. The empty string means Free.
func ParseMode(name string) (Mode, error) {
	switch m := Mode(name); m {
	case "", Free:
		return Free, nil
	case Upcoming, Deals:
		return m, nil
	default:
		return "", fmt.Errorf("unknown mode %q (free, upcoming, deals)", name)
	}
}

// List queries provs for mode.
//
// Stores without the requested capability are skipped silently (Steam has no
// upcoming window, GOG no deals). A failing store becomes a warning instead of
// aborting, so one flaky endpoint does not hide the others. The error return
// is only for an unknown mode.
func List(ctx context.Context, provs []game.Provider, mode Mode) ([]game.Game, []string, error) {
	m, err := ParseMode(string(mode))
	if err != nil {
		return nil, nil, err
	}

	var (
		all      []game.Game
		warnings []string
	)
	for _, p := range provs {
		games, err := fetch(ctx, p, m)
		if errors.Is(err, errUnsupported) {
			continue
		}
		if err != nil {
			warnings = append(warnings, fmt.Sprintf("%s: %v", p.Name(), err))
			continue
		}
		all = append(all, games...)
	}
	return all, warnings, nil
}

// errUnsupported marks a provider that cannot answer the requested mode.
var errUnsupported = errors.New("mode not supported by provider")

// fetch asks a single provider for the games of mode.
func fetch(ctx context.Context, p game.Provider, mode Mode) ([]game.Game, error) {
	switch mode {
	case Upcoming:
		u, ok := p.(game.UpcomingProvider)
		if !ok {
			return nil, errUnsupported
		}
		return u.GetUpcomingGames(ctx)
	case Deals:
		d, ok := p.(game.DealProvider)
		if !ok {
			return nil, errUnsupported
		}
		return d.GetDeals(ctx)
	default:
		return p.GetFreeGames(ctx)
	}
}