// UI handlers for vault unseal page.
package ui

import (
	"net/http"

	"git.wntrmute.dev/kyle/mcias/internal/audit"
	"git.wntrmute.dev/kyle/mcias/internal/middleware"
	"git.wntrmute.dev/kyle/mcias/internal/model"
	"git.wntrmute.dev/kyle/mcias/internal/vault"
)

// UnsealData is the view model for the unseal page.
type UnsealData struct {
	Error string
}

// handleUnsealPage renders the unseal form, or redirects to login if already unsealed.
func (u *UIServer) handleUnsealPage(w http.ResponseWriter, r *http.Request) {
	if !u.vault.IsSealed() {
		http.Redirect(w, r, "/login", http.StatusFound)
		return
	}
	u.render(w, "unseal", UnsealData{})
}

// handleUnsealPost processes the unseal form submission.
//
// Security: The passphrase is never logged. No CSRF protection is applied
// because there is no session to protect (the vault is sealed), and CSRF
// token generation depends on the master key (chicken-and-egg).
func (u *UIServer) handleUnsealPost(w http.ResponseWriter, r *http.Request) {
	if !u.vault.IsSealed() {
		http.Redirect(w, r, "/login", http.StatusFound)
		return
	}

	r.Body = http.MaxBytesReader(w, r.Body, maxFormBytes)
	if err := r.ParseForm(); err != nil {
		u.render(w, "unseal", UnsealData{Error: "invalid form data"})
		return
	}

	passphrase := r.FormValue("passphrase")
	if passphrase == "" {
		u.render(w, "unseal", UnsealData{Error: "passphrase is required"})
		return
	}

	// Derive master key from passphrase.
	masterKey, err := vault.DeriveFromPassphrase(passphrase, u.db)
	if err != nil {
		u.logger.Error("vault unseal (UI): derive key", "error", err)
		u.render(w, "unseal", UnsealData{Error: "unseal failed"})
		return
	}

	// Decrypt the signing key.
	privKey, pubKey, err := vault.DecryptSigningKey(u.db, masterKey)
	if err != nil {
		// Zero derived master key on failure.
		for i := range masterKey {
			masterKey[i] = 0
		}
		u.logger.Error("vault unseal (UI): decrypt signing key", "error", err)
		u.render(w, "unseal", UnsealData{Error: "unseal failed"})
		return
	}

	if err := u.vault.Unseal(masterKey, privKey, pubKey); err != nil {
		u.logger.Error("vault unseal (UI): state transition", "error", err)
		http.Redirect(w, r, "/login", http.StatusFound)
		return
	}

	ip := middleware.ClientIP(r, nil)
	u.writeAudit(r, model.EventVaultUnsealed, nil, nil, audit.JSON("source", "ui", "ip", ip))
	u.logger.Info("vault unsealed via UI", "ip", ip)

	http.Redirect(w, r, "/login", http.StatusFound)
}