package web

// The trusted setting modes (novox/hq ADR 0515 §4, issue 1859): which accounts Work and Personal each show,
// by the accounts' names in mail-store; Everything shows every granted account and is not set. Read fresh
// each time the page asks, like operators (config.go): a setting that cannot be read shows nothing in Work or
// Personal and says why, never another mode's mail.

import (
	"encoding/json"
	"errors"
	"fmt"
	"os"
	"strings"
)

// ModesFile is the setting as the mesh writes it.
type ModesFile struct {
	Modes map[string][]string `json:"modes"`
}

// ReadModes reads the setting modes: only work and personal, each a list of account names.
func ReadModes(path string) (map[string][]string, error) {
	if path == "" {
		return nil, errors.New("the module was started without its modes setting (MESH_MAIL_WEB_MODES)")
	}
	raw, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("the modes setting cannot be read: %w", err)
	}
	dec := json.NewDecoder(strings.NewReader(string(raw)))
	dec.DisallowUnknownFields()
	var f ModesFile
	if err := dec.Decode(&f); err != nil {
		return nil, fmt.Errorf("the modes setting is not the module's: %w", err)
	}
	for name := range f.Modes {
		if name != "work" && name != "personal" {
			return nil, fmt.Errorf("the modes setting names the mode %q; it sets work and personal alone", name)
		}
	}
	return f.Modes, nil
}

// modeAccounts answers the accounts mode shows — nil for Everything, every granted account — or why it shows
// none.
func (b *Bundle) modeAccounts(mode Mode) ([]string, string) {
	if mode.Name == "everything" {
		return nil, ""
	}
	read := func() (map[string][]string, error) { return ReadModes(b.Env.Modes) }
	if b.ModesSetting != nil {
		read = b.ModesSetting
	}
	modes, err := read()
	if err != nil {
		return nil, err.Error() + "; " + mode.Label + " shows nothing until it can be."
	}
	accounts := modes[mode.Name]
	if len(accounts) == 0 {
		return nil, "The setting modes names no account for " + mode.Label + "; Everything shows every account."
	}
	return accounts, ""
}