package httpapi

import (
	"encoding/json"
	"errors"
	"io"
	"net/http"
	"strings"

	postgresstore "knowledge-governance/internal/platform/postgres"
)

// Member administration. Every route here is classified admin by the auth
// middleware; these handlers additionally require the session identity.

type createUserRequest struct {
	Username    string `json:"username"`
	DisplayName string `json:"display_name"`
	Role        string `json:"role"`
	Password    string `json:"password"`
}

func (config Config) handleCreateUser(w http.ResponseWriter, r *http.Request) {
	identity, ok := sessionFrom(r.Context())
	if !ok {
		writeJSON(w, http.StatusUnauthorized, map[string]string{"error": "authentication required"})
		return
	}
	var input createUserRequest
	decoder := json.NewDecoder(io.LimitReader(r.Body, 1<<20))
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(&input); err != nil {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid user request"})
		return
	}
	user, err := config.Auth.Store.CreateUser(r.Context(), strings.TrimSpace(input.Username), strings.TrimSpace(input.DisplayName), input.Role, input.Password, identity.UserID, config.Now().UTC())
	switch {
	case errors.Is(err, postgresstore.ErrAuthInvalidUser):
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "username, role or password does not meet policy"})
	case errors.Is(err, postgresstore.ErrAuthDuplicateUsername):
		writeJSON(w, http.StatusConflict, map[string]string{"error": "username already exists"})
	case err != nil:
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "could not create user"})
	default:
		writeJSON(w, http.StatusCreated, map[string]any{"data": userPayload(user)})
	}
}

func (config Config) handleListUsers(w http.ResponseWriter, r *http.Request) {
	users, err := config.Auth.Store.ListAuthUsers(r.Context())
	if err != nil {
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "could not list users"})
		return
	}
	data := make([]map[string]any, 0, len(users))
	for _, user := range users {
		data = append(data, userPayload(user))
	}
	writeJSON(w, http.StatusOK, map[string]any{"data": data})
}

type updateUserRoleRequest struct {
	Role string `json:"role"`
}

func (config Config) handleUpdateUserRole(w http.ResponseWriter, r *http.Request) {
	identity, _ := sessionFrom(r.Context())
	var input updateUserRoleRequest
	decoder := json.NewDecoder(io.LimitReader(r.Body, 1<<20))
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(&input); err != nil {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid role request"})
		return
	}
	err := config.Auth.Store.SetUserRole(r.Context(), identity.UserID, r.PathValue("id"), input.Role, config.Now().UTC())
	switch {
	case errors.Is(err, postgresstore.ErrAuthInvalidUser):
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid role"})
	case errors.Is(err, postgresstore.ErrAuthUserNotFound):
		writeJSON(w, http.StatusNotFound, map[string]string{"error": "user not found"})
	case errors.Is(err, postgresstore.ErrAuthLastAdmin):
		writeJSON(w, http.StatusConflict, map[string]string{"error": "cannot change the last active admin"})
	case err != nil:
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "could not update role"})
	default:
		user, getErr := config.Auth.Store.GetAuthUserByID(r.Context(), r.PathValue("id"))
		if getErr != nil {
			writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "could not load user"})
			return
		}
		writeJSON(w, http.StatusOK, map[string]any{"data": userPayload(user)})
	}
}

type updateUserStateRequest struct {
	State string `json:"state"`
}

func (config Config) handleUpdateUserState(w http.ResponseWriter, r *http.Request) {
	identity, _ := sessionFrom(r.Context())
	var input updateUserStateRequest
	decoder := json.NewDecoder(io.LimitReader(r.Body, 1<<20))
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(&input); err != nil || (input.State != "active" && input.State != "disabled") {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "state must be active or disabled"})
		return
	}
	targetID := r.PathValue("id")
	if targetID == identity.UserID {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "cannot change your own account state"})
		return
	}
	err := config.Auth.Store.SetUserState(r.Context(), identity.UserID, targetID, input.State, config.Now().UTC())
	switch {
	case errors.Is(err, postgresstore.ErrAuthUserNotFound):
		writeJSON(w, http.StatusNotFound, map[string]string{"error": "user not found"})
	case errors.Is(err, postgresstore.ErrAuthLastAdmin):
		writeJSON(w, http.StatusConflict, map[string]string{"error": "cannot disable the last active admin"})
	case err != nil:
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "could not update account"})
	default:
		user, getErr := config.Auth.Store.GetAuthUserByID(r.Context(), targetID)
		if getErr != nil {
			writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "could not load user"})
			return
		}
		writeJSON(w, http.StatusOK, map[string]any{"data": userPayload(user)})
	}
}

type resetUserPasswordRequest struct {
	TemporaryPassword string `json:"temporary_password"`
}

func (config Config) handleResetUserPassword(w http.ResponseWriter, r *http.Request) {
	identity, _ := sessionFrom(r.Context())
	var input resetUserPasswordRequest
	decoder := json.NewDecoder(io.LimitReader(r.Body, 1<<20))
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(&input); err != nil || len(input.TemporaryPassword) < 8 {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "temporary_password must be at least 8 characters"})
		return
	}
	targetID := r.PathValue("id")
	if targetID == identity.UserID {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "use change-password for your own account"})
		return
	}
	err := config.Auth.Store.AdminResetPassword(r.Context(), identity.UserID, targetID, input.TemporaryPassword, config.Now().UTC())
	switch {
	case errors.Is(err, postgresstore.ErrAuthUserNotFound):
		writeJSON(w, http.StatusNotFound, map[string]string{"error": "user not found"})
	case errors.Is(err, postgresstore.ErrAuthUserDisabled):
		writeJSON(w, http.StatusConflict, map[string]string{"error": "cannot reset a disabled account"})
	case errors.Is(err, postgresstore.ErrAuthInvalidUser):
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid temporary password"})
	case err != nil:
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "could not reset password"})
	default:
		writeJSON(w, http.StatusOK, map[string]any{"data": map[string]bool{"reset": true, "must_change_password": true}})
	}
}

func (config Config) userRoutes(mux *http.ServeMux) {
	mux.HandleFunc("GET /api/v1/users", config.handleListUsers)
	mux.HandleFunc("POST /api/v1/users", config.handleCreateUser)
	mux.HandleFunc("POST /api/v1/users/{id}/role", config.handleUpdateUserRole)
	mux.HandleFunc("POST /api/v1/users/{id}/state", config.handleUpdateUserState)
	mux.HandleFunc("POST /api/v1/users/{id}/reset-password", config.handleResetUserPassword)
}