package main

import (
	"context"
	"database/sql"
	"encoding/json"
	"errors"
	"flag"
	"io"
	"os"
	"path/filepath"
	"strings"
	"time"

	"git.yuntuo.hk/k2safe/orbit/internal/config"
	"git.yuntuo.hk/k2safe/orbit/internal/credentialvault"
	"git.yuntuo.hk/k2safe/orbit/internal/storage/mysql"
	core "git.yuntuo.hk/k2safe/orbit/model"
)

func runCredential(args []string) error {
	if len(args) == 0 {
		return errors.New("usage: orbit-admin credential status|rotate|expiry|finalize|revoke|apply")
	}
	switch args[0] {
	case "status":
		return runCredentialStatus(args[1:])
	case "rotate":
		return runCredentialChange(args[1:], "ROTATE")
	case "expiry":
		return runCredentialChange(args[1:], "SET_EXPIRY")
	case "finalize":
		return runCredentialChange(args[1:], "FINALIZE")
	case "revoke":
		return runCredentialChange(args[1:], "REVOKE")
	case "apply":
		return runCredentialApply(args[1:])
	default:
		return errors.New("usage: orbit-admin credential status|rotate|expiry|finalize|revoke|apply")
	}
}

func runCredentialStatus(args []string) error {
	flags := flag.NewFlagSet("credential status", flag.ContinueOnError)
	namespace, credential := "", ""
	flags.StringVar(&namespace, "namespace-id", "", "credential namespace id")
	flags.StringVar(&credential, "credential-id", "", "credential id")
	if err := flags.Parse(args); err != nil {
		return err
	}
	if flags.NArg() != 0 {
		return errors.New("credential status does not accept positional arguments")
	}
	ns, id, err := credentialIDs(namespace, credential)
	if err != nil {
		return err
	}
	ctx, db, closeDB, err := adminDB(15 * time.Second)
	if err != nil {
		return err
	}
	defer closeDB()
	status, err := mysql.GetCredentialStatus(ctx, db, ns, id)
	if err != nil {
		return errors.New("credential status failed")
	}
	return json.NewEncoder(os.Stdout).Encode(status)
}

func runCredentialChange(args []string, action string) error {
	flags := flag.NewFlagSet("credential "+strings.ToLower(action), flag.ContinueOnError)
	namespace, credential, output, reason, validFor := "", "", "", "", "0"
	grace := time.Duration(0)
	if action == "ROTATE" {
		grace = 7 * 24 * time.Hour
	}
	var expected uint64
	flags.StringVar(&namespace, "namespace-id", "", "credential namespace id")
	flags.StringVar(&credential, "credential-id", "", "credential id")
	flags.Uint64Var(&expected, "expected-revision", 0, "current credential revision required for first apply")
	flags.StringVar(&reason, "reason", "", "required audit reason")
	flags.StringVar(&output, "output", "", "new private operation file; an existing file is never overwritten")
	flags.StringVar(&validFor, "valid-for", "0", "credential validity: 0 permanent, or 1h to 8760h")
	flags.DurationVar(&grace, "grace", grace, "rotation overlap: 0 immediate, up to 720h; default 168h")
	if err := flags.Parse(args); err != nil {
		return err
	}
	if flags.NArg() != 0 || output == "" {
		return errors.New("credential change requires --namespace-id, --credential-id, --expected-revision, --reason and --output")
	}
	ns, id, err := credentialIDs(namespace, credential)
	if err != nil || expected == 0 {
		return errors.New("credential change requires valid ids and a nonzero --expected-revision")
	}
	duration := time.Duration(0)
	if action == "ROTATE" || action == "SET_EXPIRY" {
		duration, err = time.ParseDuration(validFor)
		if err != nil {
			return errors.New("invalid --valid-for duration")
		}
	}
	ctx, db, closeDB, err := adminDB(30 * time.Second)
	if err != nil {
		return err
	}
	defer closeDB()
	op, err := mysql.PrepareCredentialOperation(ctx, db, mysql.CredentialChangeInput{
		NamespaceID: ns, CredentialID: id, ExpectedRevision: expected, Action: action, ValidFor: duration, GraceFor: grace, Reason: reason,
	})
	if err != nil {
		return errors.New("credential operation could not be prepared")
	}
	if err := writePrivateOperation(output, op); err != nil {
		return err
	}
	vault, err := credentialvault.LoadFile(os.Getenv("ORBIT_CREDENTIAL_KEY_FILE"))
	if err != nil {
		return err
	}
	receipt, err := mysql.ApplyCredentialOperation(ctx, db, op, vault)
	if err != nil {
		return errors.New("credential operation was not confirmed; the private operation file was retained for reconciliation")
	}
	return json.NewEncoder(os.Stdout).Encode(receipt)
}

func runCredentialApply(args []string) error {
	flags := flag.NewFlagSet("credential apply", flag.ContinueOnError)
	file := ""
	flags.StringVar(&file, "file", "", "existing private credential operation file")
	if err := flags.Parse(args); err != nil {
		return err
	}
	if flags.NArg() != 0 || file == "" {
		return errors.New("credential apply requires --file")
	}
	op, err := readPrivateOperation(file)
	if err != nil {
		return err
	}
	ctx, db, closeDB, err := adminDB(30 * time.Second)
	if err != nil {
		return err
	}
	defer closeDB()
	vault, err := credentialvault.LoadFile(os.Getenv("ORBIT_CREDENTIAL_KEY_FILE"))
	if err != nil {
		return err
	}
	receipt, err := mysql.ApplyCredentialOperation(ctx, db, op, vault)
	if err != nil {
		return errors.New("credential operation was not confirmed; retry with the same private operation file")
	}
	return json.NewEncoder(os.Stdout).Encode(receipt)
}

func credentialIDs(namespace, credential string) (core.ID, core.ID, error) {
	ns, id := core.ID(namespace), core.ID(credential)
	if ns.Validate() != nil || id.Validate() != nil {
		return "", "", errors.New("valid --namespace-id and --credential-id are required")
	}
	return ns, id, nil
}

func adminDB(timeout time.Duration) (context.Context, *sql.DB, func(), error) {
	ctx, cancel := context.WithTimeout(context.Background(), timeout)
	cfg, err := config.Load()
	if err != nil {
		cancel()
		return nil, nil, func() {}, err
	}
	db, err := mysql.Open(ctx, cfg.MySQLDSN, 2, 1)
	if err != nil {
		cancel()
		return nil, nil, func() {}, err
	}
	return ctx, db, func() { db.Close(); cancel() }, nil
}

func writePrivateOperation(path string, op mysql.CredentialOperation) error {
	if path == "" || filepath.Base(path) == "." || filepath.Base(path) == string(filepath.Separator) {
		return errors.New("invalid private operation path")
	}
	file, err := os.OpenFile(path, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0600)
	if err != nil {
		return errors.New("cannot create private operation file; existing files are never overwritten")
	}
	keep := false
	defer func() {
		_ = file.Close()
		if !keep {
			_ = os.Remove(path)
		}
	}()
	if err := file.Chmod(0600); err != nil {
		return errors.New("cannot protect private operation file")
	}
	if err := json.NewEncoder(file).Encode(op); err != nil {
		return errors.New("cannot write private operation file")
	}
	if err := file.Sync(); err != nil {
		return errors.New("cannot sync private operation file")
	}
	directory, err := os.Open(filepath.Dir(path))
	if err != nil {
		return errors.New("cannot open private operation directory")
	}
	err = directory.Sync()
	closeErr := directory.Close()
	if err != nil || closeErr != nil {
		return errors.New("cannot sync private operation directory")
	}
	keep = true
	return nil
}

func readPrivateOperation(path string) (mysql.CredentialOperation, error) {
	var op mysql.CredentialOperation
	info, err := os.Lstat(path)
	if err != nil || !info.Mode().IsRegular() || info.Mode().Perm()&0077 != 0 || info.Size() > 64*1024 {
		return op, errors.New("private operation file must be a regular 0600 file no larger than 64 KiB")
	}
	file, err := os.Open(path)
	if err != nil {
		return op, errors.New("cannot read private operation file")
	}
	defer file.Close()
	decoder := json.NewDecoder(io.LimitReader(file, 64*1024+1))
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(&op); err != nil {
		return op, errors.New("private operation file is invalid")
	}
	var extra any
	if err := decoder.Decode(&extra); err != io.EOF {
		return op, errors.New("private operation file must contain exactly one JSON object")
	}
	if err := mysql.ValidateCredentialOperation(op); err != nil {
		return op, errors.New("private operation file failed validation")
	}
	return op, nil
}