package api

import (
	"context"
	"crypto/rand"
	"crypto/sha256"
	"database/sql"
	"encoding/hex"
	"net/http"
	"strconv"
	"strings"
	"time"

	"git.ryuvia.com/niklas/terdut-server/internal/models"
	"github.com/go-chi/chi/v5"
)

func handleBootstrap(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		var req struct {
			Username string `json:"username"`
			Email    string `json:"email"`
			// Password is optional; without one the first user can only use the
			// API key until somebody sets it.
			Password string `json:"password"`
		}
		if err := decodeJSON(r, &req); err != nil {
			respond(w, http.StatusBadRequest, errResp("invalid request body"))
			return
		}
		if req.Username == "" || req.Email == "" {
			respond(w, http.StatusBadRequest, errResp("username and email are required"))
			return
		}
		var passwordHash *string
		if req.Password != "" {
			if msg := validatePassword(req.Password); msg != "" {
				respond(w, http.StatusBadRequest, errResp(msg))
				return
			}
			h, err := hashPassword(req.Password)
			if err != nil {
				respond(w, http.StatusInternalServerError, errResp("internal error"))
				return
			}
			passwordHash = &h
		}

		var count int
		if err := db.QueryRowContext(r.Context(), "SELECT COUNT(*) FROM users").Scan(&count); err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		if count > 0 {
			respond(w, http.StatusForbidden, errResp("bootstrap already completed"))
			return
		}

		var userID int64
		if err := db.QueryRowContext(r.Context(),
			"INSERT INTO users (username, email, password_hash, is_admin) VALUES ($1, $2, $3, true) RETURNING id",
			req.Username, req.Email, passwordHash).Scan(&userID); err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}

		raw, hash, err := randomToken()
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		var keyID int64
		if err := db.QueryRowContext(r.Context(),
			"INSERT INTO api_keys (user_id, key_hash, name) VALUES ($1, $2, $3) RETURNING id",
			userID, hash, "bootstrap").Scan(&keyID); err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}

		// The default team exists from migration 003, on a fresh install too.
		// Without a membership the first user signs in to a working server with
		// no queue, no schedule and nowhere for an integration to hang off.
		if teamID, err := defaultTeamID(r.Context(), db); err == nil {
			db.ExecContext(r.Context(), //nolint:errcheck
				"INSERT INTO team_members (team_id, user_id, role) VALUES ($1, $2, $3) "+
					"ON CONFLICT (team_id, user_id) DO NOTHING",
				teamID, userID, models.RoleOwner)
		}

		user, _ := fetchUser(r.Context(), db, userID)
		key := models.APIKey{ID: keyID, UserID: userID, Name: "bootstrap", Key: raw, CreatedAt: user.CreatedAt}
		respond(w, http.StatusCreated, map[string]any{"user": user, "api_key": key})
	}
}

func handleListUsers(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		rows, err := db.QueryContext(r.Context(),
			"SELECT id, username, email, created_at, ntfy_topic, is_admin FROM users ORDER BY id")
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		defer rows.Close()

		users := []models.User{}
		for rows.Next() {
			var u models.User
			var ts int64
			if err := rows.Scan(&u.ID, &u.Username, &u.Email, &ts, &u.NtfyTopic, &u.IsAdmin); err != nil {
				respond(w, http.StatusInternalServerError, errResp("internal error"))
				return
			}
			u.CreatedAt = time.Unix(ts, 0).UTC()
			users = append(users, u)
		}
		respond(w, http.StatusOK, users)
	}
}

func handleCreateUser(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		var req struct {
			Username string `json:"username"`
			Email    string `json:"email"`
		}
		if err := decodeJSON(r, &req); err != nil {
			respond(w, http.StatusBadRequest, errResp("invalid request body"))
			return
		}
		if req.Username == "" || req.Email == "" {
			respond(w, http.StatusBadRequest, errResp("username and email are required"))
			return
		}

		var id int64
		if err := db.QueryRowContext(r.Context(),
			"INSERT INTO users (username, email) VALUES ($1, $2) RETURNING id",
			req.Username, req.Email).Scan(&id); err != nil {
			if isUniqueViolation(err) {
				respond(w, http.StatusConflict, errResp("username or email already exists"))
				return
			}
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		user, _ := fetchUser(r.Context(), db, id)
		respond(w, http.StatusCreated, user)
	}
}

// handleSetNotifyTarget points a user's push notifications at an ntfy topic, or
// clears it with an empty string. The topic is a shared secret with the ntfy
// server — anyone who knows it can publish to it — so pick an unguessable one
// unless your ntfy enforces access control.
func handleSetNotifyTarget(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		id, err := strconv.ParseInt(chi.URLParam(r, "id"), 10, 64)
		if err != nil {
			respond(w, http.StatusBadRequest, errResp("invalid user id"))
			return
		}
		if !requireSelfOrAdmin(w, r, id) {
			return
		}
		var req struct {
			NtfyTopic string `json:"ntfy_topic"`
		}
		if err := decodeJSON(r, &req); err != nil {
			respond(w, http.StatusBadRequest, errResp("invalid request body"))
			return
		}

		var topic *string
		if t := strings.TrimSpace(req.NtfyTopic); t != "" {
			topic = &t
		}

		res, err := db.ExecContext(r.Context(),
			"UPDATE users SET ntfy_topic = $1 WHERE id = $2", topic, id)
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		if n, _ := res.RowsAffected(); n == 0 {
			respond(w, http.StatusNotFound, errResp("user not found"))
			return
		}

		user, err := fetchUser(r.Context(), db, id)
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		respond(w, http.StatusOK, user)
	}
}

func handleDeleteUser(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		id, err := strconv.ParseInt(chi.URLParam(r, "id"), 10, 64)
		if err != nil {
			respond(w, http.StatusBadRequest, errResp("invalid user id"))
			return
		}
		// Deleting yourself is how an install ends up with no administrator at
		// all, and it is never what somebody meant to do.
		caller, _ := userFromContext(r.Context())
		if caller.ID == id {
			respond(w, http.StatusConflict, errResp("cannot delete your own account"))
			return
		}
		if last, err := isLastAdmin(r.Context(), db, id); err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		} else if last {
			respond(w, http.StatusConflict, errResp("cannot delete the last administrator"))
			return
		}

		res, err := db.ExecContext(r.Context(), "DELETE FROM users WHERE id = $1", id)
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		n, _ := res.RowsAffected()
		if n == 0 {
			respond(w, http.StatusNotFound, errResp("user not found"))
			return
		}
		w.WriteHeader(http.StatusNoContent)
	}
}

func handleCreateAPIKey(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		userID, err := strconv.ParseInt(chi.URLParam(r, "id"), 10, 64)
		if err != nil {
			respond(w, http.StatusBadRequest, errResp("invalid user id"))
			return
		}
		if !requireSelfOrAdmin(w, r, userID) {
			return
		}

		var req struct {
			Name string `json:"name"`
		}
		if err := decodeJSON(r, &req); err != nil {
			respond(w, http.StatusBadRequest, errResp("invalid request body"))
			return
		}
		if req.Name == "" {
			respond(w, http.StatusBadRequest, errResp("name is required"))
			return
		}

		var exists int
		if err := db.QueryRowContext(r.Context(), "SELECT 1 FROM users WHERE id = $1", userID).Scan(&exists); err != nil {
			respond(w, http.StatusNotFound, errResp("user not found"))
			return
		}

		raw, hash, err := randomToken()
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		var keyID int64
		if err := db.QueryRowContext(r.Context(),
			"INSERT INTO api_keys (user_id, key_hash, name) VALUES ($1, $2, $3) RETURNING id",
			userID, hash, req.Name).Scan(&keyID); err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		key := models.APIKey{ID: keyID, UserID: userID, Name: req.Name, Key: raw, CreatedAt: time.Now().UTC()}
		respond(w, http.StatusCreated, key)
	}
}

func handleDeleteAPIKey(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		userID, err := strconv.ParseInt(chi.URLParam(r, "id"), 10, 64)
		if err != nil {
			respond(w, http.StatusBadRequest, errResp("invalid user id"))
			return
		}
		if !requireSelfOrAdmin(w, r, userID) {
			return
		}
		keyID, err := strconv.ParseInt(chi.URLParam(r, "keyID"), 10, 64)
		if err != nil {
			respond(w, http.StatusBadRequest, errResp("invalid key id"))
			return
		}

		res, err := db.ExecContext(r.Context(),
			"DELETE FROM api_keys WHERE id = $1 AND user_id = $2", keyID, userID)
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		n, _ := res.RowsAffected()
		if n == 0 {
			respond(w, http.StatusNotFound, errResp("api key not found"))
			return
		}
		w.WriteHeader(http.StatusNoContent)
	}
}

// randomToken generates a random 32-byte secret encoded as hex, plus its SHA-256
// hash for storage. Used for API keys and for notification acknowledge tokens.
func randomToken() (raw, hash string, err error) {
	b := make([]byte, 32)
	if _, err = rand.Read(b); err != nil {
		return
	}
	raw = hex.EncodeToString(b)
	h := sha256.Sum256([]byte(raw))
	hash = hex.EncodeToString(h[:])
	return
}

func fetchUser(ctx context.Context, db *sql.DB, id int64) (models.User, error) {
	var u models.User
	var ts int64
	err := db.QueryRowContext(ctx,
		"SELECT id, username, email, created_at, ntfy_topic, is_admin FROM users WHERE id = $1", id).
		Scan(&u.ID, &u.Username, &u.Email, &ts, &u.NtfyTopic, &u.IsAdmin)
	if err != nil {
		return u, err
	}
	u.CreatedAt = time.Unix(ts, 0).UTC()
	return u, nil
}

// handleSetAdmin grants or revokes the system administrator flag.
//
// Revoking is guarded twice: an install must keep at least one administrator,
// and you cannot demote yourself. The first stops the flag being lost
// altogether; the second stops the likelier accident, where the only admin
// clears their own flag while tidying up and locks the door behind them.
func handleSetAdmin(db *sql.DB) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		id, err := strconv.ParseInt(chi.URLParam(r, "id"), 10, 64)
		if err != nil {
			respond(w, http.StatusBadRequest, errResp("invalid user id"))
			return
		}
		var req struct {
			IsAdmin *bool `json:"is_admin"`
		}
		if err := decodeJSON(r, &req); err != nil || req.IsAdmin == nil {
			respond(w, http.StatusBadRequest, errResp("is_admin is required"))
			return
		}

		if !*req.IsAdmin {
			caller, _ := userFromContext(r.Context())
			if caller.ID == id {
				respond(w, http.StatusConflict, errResp("cannot revoke your own administrator access"))
				return
			}
			if last, err := isLastAdmin(r.Context(), db, id); err != nil {
				respond(w, http.StatusInternalServerError, errResp("internal error"))
				return
			} else if last {
				respond(w, http.StatusConflict, errResp("cannot revoke the last administrator"))
				return
			}
		}

		res, err := db.ExecContext(r.Context(),
			"UPDATE users SET is_admin = $1 WHERE id = $2", *req.IsAdmin, id)
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		if n, _ := res.RowsAffected(); n == 0 {
			respond(w, http.StatusNotFound, errResp("user not found"))
			return
		}

		user, err := fetchUser(r.Context(), db, id)
		if err != nil {
			respond(w, http.StatusInternalServerError, errResp("internal error"))
			return
		}
		respond(w, http.StatusOK, user)
	}
}

// isLastAdmin reports whether id is an administrator and no other user is one.
// A non-admin id is never the last one, so removing them is always allowed.
func isLastAdmin(ctx context.Context, db *sql.DB, id int64) (bool, error) {
	var last bool
	err := db.QueryRowContext(ctx, `
		SELECT EXISTS (SELECT 1 FROM users WHERE id = $1 AND is_admin)
		   AND NOT EXISTS (SELECT 1 FROM users WHERE id <> $1 AND is_admin)`, id).Scan(&last)
	return last, err
}