package main

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

	"github.com/golang-jwt/jwt/v5"
	"golang.org/x/crypto/bcrypt"
)

type Claims struct {
	ParticipantID int      `json:"pid"`
	Email         string   `json:"sub"`
	Roles         []string `json:"roles"`
	DeptIDs       []int    `json:"dept_ids,omitempty"`
	jwt.RegisteredClaims
}

func hashPassword(password string) (string, error) {
	b, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
	return string(b), err
}

func checkPassword(hash, password string) bool {
	return bcrypt.CompareHashAndPassword([]byte(hash), []byte(password)) == nil
}

func (app *App) signToken(s *User) (string, error) {
	expiry := time.Duration(app.tokenExpiry) * time.Hour
	claims := Claims{
		ParticipantID: s.ID,
		Email:         s.Email,
		Roles:         s.Roles,
		DeptIDs:       s.DepartmentIDs,
		RegisteredClaims: jwt.RegisteredClaims{
			ExpiresAt: jwt.NewNumericDate(time.Now().Add(expiry)),
			IssuedAt:  jwt.NewNumericDate(time.Now()),
		},
	}
	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
	return token.SignedString([]byte(app.secret))
}

func (app *App) parseToken(tokenStr string) (*Claims, error) {
	token, err := jwt.ParseWithClaims(tokenStr, &Claims{}, func(t *jwt.Token) (any, error) {
		if _, ok := t.Method.(*jwt.SigningMethodHMAC); !ok {
			return nil, jwt.ErrSignatureInvalid
		}
		return []byte(app.secret), nil
	})
	if err != nil {
		return nil, err
	}
	claims, ok := token.Claims.(*Claims)
	if !ok || !token.Valid {
		return nil, jwt.ErrTokenInvalidClaims
	}
	return claims, nil
}

func bearerToken(r *http.Request) string {
	h := r.Header.Get("Authorization")
	if strings.HasPrefix(h, "Bearer ") {
		return strings.TrimPrefix(h, "Bearer ")
	}
	// Fallback to query param for SSE (EventSource can't set headers)
	return r.URL.Query().Get("token")
}

// requireAuth wraps a handler, injects claims into context via X-Claims header trick.
// We pass claims via a request-scoped value instead.
type contextKey string

const claimsKey contextKey = "claims"

func (app *App) requireAuth(next http.HandlerFunc, roles ...string) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		token := bearerToken(r)
		if token == "" {
			writeError(w, "unauthorized", http.StatusUnauthorized)
			return
		}
		claims, err := app.parseToken(token)
		if err != nil {
			writeError(w, "unauthorized", http.StatusUnauthorized)
			return
		}
		if len(roles) > 0 && !hasAnyRole(claims.Roles, roles) {
			writeError(w, "forbidden", http.StatusForbidden)
			return
		}
		ctx := context.WithValue(r.Context(), claimsKey, claims)
		next(w, r.WithContext(ctx))
	}
}

func hasAnyRole(roles []string, allowed []string) bool {
	for _, r := range roles {
		for _, a := range allowed {
			if r == a {
				return true
			}
		}
	}
	return false
}

func isCoLeadOnly(claims *Claims) bool {
	return hasAnyRole(claims.Roles, []string{"colead"}) &&
		!hasAnyRole(claims.Roles, []string{"admin", "staffing"})
}

func inSlice(v int, s []int) bool {
	for _, x := range s {
		if x == v {
			return true
		}
	}
	return false
}

func claimsFromContext(r *http.Request) *Claims {
	c, _ := r.Context().Value(claimsKey).(*Claims)
	return c
}

func writeJSON(w http.ResponseWriter, v any) {
	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(v)
}

func writeError(w http.ResponseWriter, msg string, code int) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(code)
	json.NewEncoder(w).Encode(map[string]string{"error": msg})
}