package backup

import (
	"bufio"
	"context"
	"fmt"
	"io"
	"os"
	"strings"
	"time"
)

// R-200 — the operator-facing entry point for the recovery check, and the ONLY one this session
// ships. Deliberately a `docker exec` escape hatch in the shape of `--print-reset-code`, not a page,
// a card or an API a browser can reach: the customer-facing flow is designed on top of a chain that
// has been walked, and this is the walk.
//
// WHY R COMES FROM STDIN AND NOT A FLAG. A flag value is visible in `ps`, in the shell history, in a
// container's command line and in any transcript of the session that ran it. R is the one secret in
// this system that cannot be rotated, re-issued or recovered. It is read from stdin, held in one
// string, and cleared before the function returns — on the success path and on every failure path.
//
//	docker exec -i felhom-controller /app/felhom-controller --recover-offsite-check < /root/r.txt
//
// WHAT IT PRINTS: two sha256 hashes and a verdict. Never a password, never R, never a blob. The
// hashes are of 256-bit random secrets and are non-reversible — the same value the hub already stores
// and serves in report ACKs.

// RecoveryCheckDeps is what the CLI needs; injected so the entry point is testable without a live
// agent, a live hub or real crypto.
type RecoveryCheckDeps struct {
	// Manager owns the on-disk repo password hash.
	Manager *Manager
	// Recoverer is the agent seam (agentapi.Client satisfies it).
	Recoverer OffsiteKeyRecoverer
	// In is where R is read from (os.Stdin in production).
	In io.Reader
	// Out / Err are the report streams (os.Stdout / os.Stderr in production).
	Out, Err io.Writer
	// Timeout bounds the whole check. 0 → 90s (an unseal shells out to age and a fetch crosses the WAN).
	Timeout time.Duration
}

// RunRecoveryCheck reads R from stdin, recovers the offsite repository password through the agent,
// and reports whether it matches the one on disk — BY HASH. Returns a process exit code:
//
//	0 = the hashes matched (the key is recoverable)
//	1 = a step failed (fetch, unseal, or no local password to compare against)
//	2 = the check ran cleanly and the hashes DIFFER — the loud case, and the one that would mean the
//	    sealed bundle does not carry what four weeks of documents say it carries
//
// A distinct code for the mismatch on purpose: "it failed" and "it worked and disagreed" must never
// share an exit status, because only one of them is a finding about the system rather than about the
// run.
func RunRecoveryCheck(d RecoveryCheckDeps) int {
	out, errw := d.Out, d.Err
	if out == nil {
		out = os.Stdout
	}
	if errw == nil {
		errw = os.Stderr
	}
	if d.Manager == nil || d.Recoverer == nil {
		fmt.Fprintln(errw, "recover-offsite-check: not configured (no backup manager or no agent channel)")
		return 1
	}
	in := d.In
	if in == nil {
		in = os.Stdin
	}
	// Read R: the first line of stdin, trimmed. A 10-word EFF code contains spaces, so only the
	// line ending is stripped — never internal whitespace.
	br := bufio.NewReader(io.LimitReader(in, 4096))
	line, rerr := br.ReadString('\n')
	R := strings.TrimRight(line, "\r\n")
	if R == "" {
		fmt.Fprintln(errw, "recover-offsite-check: no recovery code on stdin. Pipe it in:")
		fmt.Fprintln(errw, "  docker exec -i felhom-controller /app/felhom-controller --recover-offsite-check < /path/to/code")
		if rerr != nil && rerr != io.EOF {
			fmt.Fprintf(errw, "  (read error: %v)\n", rerr)
		}
		return 1
	}

	timeout := d.Timeout
	if timeout == 0 {
		timeout = 90 * time.Second
	}
	ctx, cancel := context.WithTimeout(context.Background(), timeout)
	defer cancel()

	fmt.Fprintln(out, "=== offsite key recovery check (R-200) — compares, never installs ===")
	res, err := d.Manager.CheckOffsiteKeyRecoverable(ctx, d.Recoverer, R)
	R = "" // cleared before anything else, on every path below
	if err != nil {
		fmt.Fprintf(errw, "  [FAIL] %v\n", err) // the agent's message names the step; it carries no secret
		fmt.Fprintln(errw, "  nothing was written.")
		return 1
	}
	if !res.LocalPresent {
		fmt.Fprintln(errw, "  [FAIL] there is no repository password on this box to compare against")
		fmt.Fprintf(out, "  recovered sha256: %s\n", res.RecoveredSHA256)
		fmt.Fprintln(errw, "  (the recovery itself SUCCEEDED — this box simply has no local key. That is the")
		fmt.Fprintln(errw, "   rebuilt-box shape, where the next step is to INSTALL rather than compare.)")
		return 1
	}
	fmt.Fprintf(out, "  on-disk   sha256: %s\n", res.LocalSHA256)
	fmt.Fprintf(out, "  recovered sha256: %s\n", res.RecoveredSHA256)
	if !res.Match {
		fmt.Fprintln(errw, "  [MISMATCH] the recovered key is NOT the key this box uses.")
		fmt.Fprintln(errw, "  This is a finding about the system, not about the run: the sealed bundle does not")
		fmt.Fprintln(errw, "  carry the repository password this box's off-site history is encrypted under.")
		return 2
	}
	fmt.Fprintln(out, "  [MATCH] the offsite repository password IS recoverable from the sealed escrow.")
	fmt.Fprintln(out, "  Nothing was written: this check compares and never installs.")
	return 0
}

// RecoverAndInstall is the sibling of RunRecoveryCheck that PLACES the recovered repository password,
// so a rebuilt box can reopen the off-site history it inherited (R-200's remaining plumbing half).
//
// WHY THIS IS CODE AND NOT A MANUAL STEP. The alternative — recover the password, read it off a
// terminal, and paste it into the injection endpoint by hand — puts the offsite DATA key through a
// human's screen, clipboard and shell history. Doing it in-process is both simpler and strictly
// safer: the value goes agent → this process → the 0600 file and is never rendered anywhere.
//
// THE CONFIRMATION IS A SEPARATE INVOCATION, ON PURPOSE. Without `confirm` this prints the two hashes
// and writes nothing — the operator sees the comparison BEFORE any write exists as a possibility.
// With `confirm` it prints the same hashes and then installs. A single interactive prompt would have
// had to share stdin with R, which is where R must not be competing for attention.
//
// THREE OUTCOMES, NAMED DISTINCTLY, because "it did nothing" and "it refused" are different facts:
//
//	installed  — this box had NO repository password (the rebuilt-box shape). The recovered one is placed.
//	unchanged  — a password is present and is byte-identical to the recovered one. Nothing is written.
//	refused    — a password is present and DIFFERS. Installing would clobber the key this box's CURRENT
//	             repository is encrypted under, so it is refused. No force option is offered here: that
//	             decision needs a human who knows which history they intend to keep.
// RecoverInstallOutcome names the terminal states of a recovery+install. Distinct values because
// "it did nothing", "it refused" and "it installed" are different facts and a caller — CLI or web —
// must be able to say which happened without parsing prose.
type RecoverInstallOutcome string

const (
	// RecoverInstalled — the box had NO repository password; the recovered one is now in place.
	RecoverInstalled RecoverInstallOutcome = "installed"
	// RecoverUnchanged — a password was present and is byte-identical to the recovered one.
	RecoverUnchanged RecoverInstallOutcome = "unchanged"
	// RecoverRefused — a DIFFERENT password is present; installing would clobber the key the box's
	// current repository is encrypted under.
	RecoverRefused RecoverInstallOutcome = "refused"
	// RecoverDryRun — nothing was written because confirm was false.
	RecoverDryRun RecoverInstallOutcome = "dry_run"
)

// RecoverInstallResult is the non-secret outcome of a recovery. It carries HASHES ONLY — never the
// password, never R. The hashes are of 256-bit random secrets, non-reversible, and are the same
// values the hub already stores and serves in report ACKs.
type RecoverInstallResult struct {
	Outcome         RecoverInstallOutcome
	LocalPresent    bool
	LocalSHA256     string
	RecoveredSHA256 string
}

// RecoverInstallCore is THE recovery+install path in this codebase — fetch the sealed bundle through
// the agent, unseal it with R, compare against what is on disk, and place it when that is the right
// thing to do.
//
// ONE FUNCTION, TWO CALLERS (R-193). The CLI (`--recover-offsite-install`) and the customer's recovery
// page both call this. They must not each carry a copy: two implementations of the one operation that
// can permanently lose a customer's data would drift, and only one of them would ever be tested.
// `RecoverAndInstall` below is a thin wrapper that maps this result onto the CLI's exit codes and
// printed lines; the web handler maps it onto Hungarian copy. Neither contains recovery logic.
//
// R IS THE CALLER'S TO CLEAR. This function does not retain it: it is passed to the agent seam and
// never stored, logged or returned. The password recovered from the bundle IS cleared here, on every
// path, before returning — it never leaves this function in any form.
//
// The three outcomes and their reasoning are unchanged from the CLI's original implementation; see
// RecoverAndInstall's header, which remains the authority on WHY a differing local password is
// refused rather than forced.
func RecoverInstallCore(ctx context.Context, m *Manager, rec OffsiteKeyRecoverer, R string, confirm bool) (RecoverInstallResult, error) {
	var res RecoverInstallResult
	if m == nil || rec == nil {
		return res, fmt.Errorf("recovery not configured (no backup manager or no agent channel)")
	}
	pw, recoveredHash, err := rec.RecoverOffsiteRepoPassword(ctx, R)
	if err != nil {
		return res, err // the agent's message names the step; it carries no secret
	}
	res.RecoveredSHA256 = recoveredHash
	res.LocalSHA256, res.LocalPresent = m.OffboxRepoPasswordHash()

	switch {
	case res.LocalPresent && res.LocalSHA256 == recoveredHash:
		pw = ""
		res.Outcome = RecoverUnchanged
		return res, nil
	case res.LocalPresent:
		pw = ""
		res.Outcome = RecoverRefused
		return res, nil
	}
	if !confirm {
		pw = ""
		res.Outcome = RecoverDryRun
		return res, nil
	}
	if err := m.InjectOffboxPassword(pw, false); err != nil {
		pw = ""
		return res, fmt.Errorf("placing the recovered password: %w", err)
	}
	pw = ""
	// Re-read from disk rather than trusting what we just wrote — the observable is the file's state.
	afterHash, ok := m.OffboxRepoPasswordHash()
	if !ok || afterHash != recoveredHash {
		return res, fmt.Errorf("the password was written but does not read back as expected (on-disk %q)", afterHash)
	}
	res.Outcome = RecoverInstalled
	return res, nil
}

func RecoverAndInstall(d RecoveryCheckDeps, confirm bool) int {
	out, errw := d.Out, d.Err
	if out == nil {
		out = os.Stdout
	}
	if errw == nil {
		errw = os.Stderr
	}
	if d.Manager == nil || d.Recoverer == nil {
		fmt.Fprintln(errw, "recover-offsite-install: not configured (no backup manager or no agent channel)")
		return 1
	}
	in := d.In
	if in == nil {
		in = os.Stdin
	}
	br := bufio.NewReader(io.LimitReader(in, 4096))
	line, rerr := br.ReadString('\n')
	R := strings.TrimRight(line, "\r\n")
	if R == "" {
		fmt.Fprintln(errw, "recover-offsite-install: no recovery code on stdin. Pipe it in:")
		fmt.Fprintln(errw, "  docker exec -i felhom-controller /usr/local/bin/felhom-controller --recover-offsite-install [--confirm-install] < /path/to/code")
		if rerr != nil && rerr != io.EOF {
			fmt.Fprintf(errw, "  (read error: %v)\n", rerr)
		}
		return 1
	}
	timeout := d.Timeout
	if timeout == 0 {
		timeout = 90 * time.Second
	}
	ctx, cancel := context.WithTimeout(context.Background(), timeout)
	defer cancel()

	fmt.Fprintln(out, "=== offsite key recovery INSTALL (R-200) ===")
	// THE RECOVERY ITSELF IS RecoverInstallCore — the same function the customer's recovery page
	// drives (R-193). This wrapper adds the CLI's stdin handling, its printed lines and its exit
	// codes, and NOTHING else; there is exactly one fetch→unseal→compare→install path in this
	// codebase and no chance of the two callers drifting. Pinned by
	// TestRecoverAndInstall_DrivesTheSharedCore and by the AST wiring test.
	res, err := RecoverInstallCore(ctx, d.Manager, d.Recoverer, R, confirm)
	R = "" // cleared immediately, on every path below
	if err != nil {
		fmt.Fprintf(errw, "  [FAIL] %v\n", err)
		fmt.Fprintln(errw, "  nothing was written.")
		return 1
	}
	if res.LocalPresent {
		fmt.Fprintf(out, "  on-disk   sha256: %s\n", res.LocalSHA256)
	} else {
		fmt.Fprintln(out, "  on-disk   sha256: (none — this box has no repository password)")
	}
	fmt.Fprintf(out, "  recovered sha256: %s\n", res.RecoveredSHA256)

	switch res.Outcome {
	case RecoverUnchanged:
		fmt.Fprintln(out, "  [UNCHANGED] the box already holds exactly this key. Nothing written.")
		return 0
	case RecoverRefused:
		fmt.Fprintln(errw, "  [REFUSED] a DIFFERENT repository password is already present.")
		fmt.Fprintln(errw, "  Installing would clobber the key this box's current repository is encrypted under,")
		fmt.Fprintln(errw, "  and which history to keep is not a decision this command may take. Nothing written.")
		return 2
	case RecoverDryRun:
		fmt.Fprintln(out, "  [DRY RUN] nothing written. The recovered key is ready to install.")
		fmt.Fprintln(out, "  Re-run with --confirm-install to place it.")
		return 0
	}
	fmt.Fprintln(out, "  [INSTALLED] the recovered repository password is in place and reads back identical.")
	fmt.Fprintln(out, "  Re-apply the offsite target and run a backup: the existing repository should open.")
	return 0
}