package api

import (
	"context"
	"fmt"

	"git.ryuvia.com/niklas/terdut-server/internal/models"
)

// Caller is the one principal type every authorization predicate in this
// package reads from. Before this, a human (ctxUser + ctxTeams) and a
// service account (ctxServiceAccount + a synthetic ctxTeams entry) were two
// parallel, un-unified context representations — every predicate had to
// remember which one(s) it needed to check, and the ones that forgot either
// 403'd a service account that should have been let through (terdut-server#23,
// terdut-operator#3), crashed on an unchecked zero-value user ID (handleMe,
// handleTestNotification), or silently no-op'd (handleDismissOnboarding).
// serveAs and serveAsServiceAccount now both build exactly one Caller and
// store it under one context key; everything else in this file is a read
// of one of its methods.
type Caller struct {
	// user is set for a human caller (session cookie or a user's own API
	// key), nil for a service account of either scope.
	user *models.User

	// sa is set for a service-account caller, nil for a human.
	sa *serviceAccountPrincipal

	// memberships is the caller's real team_members rows for a human, or —
	// for a team-scoped service account — the single synthetic owner
	// membership serveAsServiceAccount injects (see its own comment for
	// why). Always nil for an instance-scoped service account: it acts on
	// teams by id, not by belonging to one.
	memberships []membership
}

// AsHuman returns the real user behind this caller, or false for a service
// account of either scope. Every handler that needs a real user_id to act
// on behalf of — not just "is this caller sufficiently privileged" — calls
// this and handles the false case explicitly, replacing the unchecked
// userFromContext(ctx) zero-value reads that used to silently misbehave for
// a service-account caller.
func (c Caller) AsHuman() (models.User, bool) {
	if c.user == nil {
		return models.User{}, false
	}
	return *c.user, true
}

// IsAdmin is true only for a human system administrator — never for a
// service account, of either scope, under any circumstance. AdminOnly and
// requireSelfOrAdmin key on this and nothing else: user management and
// /api/admin/settings stay human-only forever, by design (SERVICE-ACCOUNTS.md).
func (c Caller) IsAdmin() bool {
	return c.user != nil && c.user.IsAdmin
}

// IsInstanceServiceAccount reports whether this caller is specifically an
// instance-scoped service account — never true for a human, including a
// human admin. handleCreateTeam needs exactly this: a human creates a team
// by being a human (and becomes its owner as a side effect), an
// instance-scoped service account creates one with no human owner at all;
// the two paths are not interchangeable, so this predicate must not also
// admit a human admin the way MayActAsInstanceAdmin deliberately does.
func (c Caller) IsInstanceServiceAccount() bool {
	return c.sa != nil && c.sa.scope == models.ServiceAccountScopeInstance
}

// Role reports the caller's role in teamID, and whether they belong to it
// at all.
func (c Caller) Role(teamID int64) (string, bool) {
	for _, m := range c.memberships {
		if m.teamID == teamID {
			return m.role, true
		}
	}
	return "", false
}

// TeamIDs lists every team this caller belongs to: a human's real
// memberships, or a team-scoped service account's own single team. Always
// empty for an instance-scoped service account.
func (c Caller) TeamIDs() []int64 {
	ids := make([]int64, 0, len(c.memberships))
	for _, m := range c.memberships {
		ids = append(ids, m.teamID)
	}
	return ids
}

// ServiceAccountID reports this caller's own service-account id, for the
// "may manage/rotate its own credential" self-check in
// callerMayManageServiceAccount, and for OperatorModeBlock's "any service
// account passes" rule.
func (c Caller) ServiceAccountID() (int64, bool) {
	if c.sa == nil {
		return 0, false
	}
	return c.sa.id, true
}

// Identity is a stable, log/audit-facing string distinguishing a human
// caller from a service account — "user:42" or "service-account:7". Not
// wired into any database column today (incidents.go's acknowledged_by/
// assigned_to/user_id are explicitly out of scope for this change — that
// needs its own schema migration, tracked separately), but this is the one
// place in the request path that already knows which kind of caller this
// is, and that follow-up will want exactly this accessor.
func (c Caller) Identity() string {
	switch {
	case c.user != nil:
		return fmt.Sprintf("user:%d", c.user.ID)
	case c.sa != nil:
		return fmt.Sprintf("service-account:%d", c.sa.id)
	default:
		return "unknown"
	}
}

func callerFromContext(ctx context.Context) (Caller, bool) {
	c, ok := ctx.Value(ctxCaller).(Caller)
	return c, ok
}