package handlers

import (
	"context"
	"encoding/json"
	"strings"
)

// PermissionHandler handles session/request_permission (spec §5.1).
//
// MVP behaviour (decision §1 #8 + §10 misc #1): fs.* tool calls are answered
// directly by the server (so they never reach this handler). Other tool calls
// default to "reject_once" — fully automated, no human-in-the-loop.
type PermissionHandler struct{}

// NewPermissionHandler constructs a PermissionHandler.
func NewPermissionHandler() *PermissionHandler { return &PermissionHandler{} }

type permissionParams struct {
	SessionID string          `json:"sessionId"`
	ToolCall  json.RawMessage `json:"toolCall"`
	Options   []permOption    `json:"options"`
}

type permOption struct {
	ID   string `json:"id"`
	Name string `json:"name,omitempty"`
}

type permOutcomeSelected struct {
	ID string `json:"id"`
}

type permOutcome struct {
	Selected *permOutcomeSelected `json:"selected,omitempty"`
}

type permResult struct {
	Outcome permOutcome `json:"outcome"`
}

// Handle picks the first option whose ID looks like a "reject" choice; if none
// matches, falls back to the first option. Aligns with spec §10 misc #4
// ("default reject").
func (h *PermissionHandler) Handle(_ context.Context, _ SessionContext, paramsJSON json.RawMessage) FsResult {
	var p permissionParams
	if err := json.Unmarshal(paramsJSON, &p); err != nil {
		return FsResult{Err: &FsError{Code: -32602, Message: "invalid params: " + err.Error()}}
	}
	chosen := ""
	for _, opt := range p.Options {
		lc := strings.ToLower(opt.ID)
		if strings.Contains(lc, "reject") || strings.Contains(lc, "deny") || strings.Contains(lc, "no") {
			chosen = opt.ID
			break
		}
	}
	if chosen == "" && len(p.Options) > 0 {
		chosen = p.Options[0].ID
	}
	if chosen == "" {
		out, _ := json.Marshal(permResult{Outcome: permOutcome{}})
		return FsResult{OK: out}
	}
	out, _ := json.Marshal(permResult{Outcome: permOutcome{Selected: &permOutcomeSelected{ID: chosen}}})
	return FsResult{OK: out}
}