package controller

import (
	"bytes"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"os"
	"strings"
	"sync"
	"time"

	"github.com/heicode/manager/common"
	"github.com/heicode/manager/model"
)

// Secret lifecycle (issue #4). Beyond the revoke-time delete already shipped in
// DeleteResource, this file closes the remaining lifecycle:
//   1. revokeUserResourceSecrets — on account disable/delete, soft-delete ALL of
//      the user's resource-bound Key Vault secrets (full cleanup, not just DB).
//   2. StartSecretPurgeTask — daily job that PERMANENTLY purges vault secrets
//      soft-deleted ≥ retention (default 30 days): the "30-day delete / render
//      unrecoverable" requirement.
//   3. rotation — UpsertResourceSecret re-PUTs a credential, which Azure stores
//      as a new version (rotateSecret == putSecret); see resource.go.

// revokeUserResourceSecrets revokes every still-active resource binding owned by
// userID and best-effort soft-deletes its Key Vault material, so disabling or
// deleting an account never leaves live credentials in the vault. The DB revoke
// is authoritative and committed first; a Key Vault outage is logged but never
// blocks account management. Returns the number of secrets soft-deleted.
func revokeUserResourceSecrets(userID int) int {
	if userID <= 0 || model.DB == nil {
		return 0
	}
	var bindings []model.ResourceBinding
	if err := model.DB.
		Where("user_id = ? AND secret_ref <> '' AND status <> ?", userID, "revoked").
		Find(&bindings).Error; err != nil {
		common.SysLog(fmt.Sprintf("revokeUserResourceSecrets: list bindings for user %d failed: %s", userID, err.Error()))
		return 0
	}
	if len(bindings) == 0 {
		return 0
	}
	ids := make([]int, 0, len(bindings))
	for _, b := range bindings {
		ids = append(ids, b.Id)
	}
	if err := model.DB.Model(&model.ResourceBinding{}).Where("id IN ?", ids).
		Update("status", "revoked").Error; err != nil {
		common.SysLog(fmt.Sprintf("revokeUserResourceSecrets: mark revoked for user %d failed: %s", userID, err.Error()))
	}
	store, sErr := newSecretStoreClientFromEnv()
	if sErr != nil {
		common.SysLog(fmt.Sprintf("revokeUserResourceSecrets: secret store unavailable, %d KV secrets NOT deleted for user %d: %s", len(bindings), userID, sErr.Error()))
		return 0
	}
	deleted := 0
	for _, b := range bindings {
		if dErr := store.deleteSecret(b.SecretRef); dErr != nil {
			common.SysLog(fmt.Sprintf("revokeUserResourceSecrets: KV delete failed for binding %d (user %d): %s", b.Id, userID, dErr.Error()))
			continue
		}
		deleted++
	}
	common.SysLog(fmt.Sprintf("revokeUserResourceSecrets: user %d — %d bindings revoked, %d KV secrets soft-deleted", userID, len(bindings), deleted))
	return deleted
}

// ── 30-day purge ────────────────────────────────────────────────────────────

type deletedSecretInfo struct {
	name        string
	deletedDate int64 // unix seconds, from Azure KV
}

// parseDeletedSecretsPage parses one page of Azure KV GET /deletedsecrets and
// returns the secrets + the nextLink (empty when no more pages). Pure (testable).
func parseDeletedSecretsPage(body []byte) ([]deletedSecretInfo, string, error) {
	var page struct {
		Value []struct {
			RecoveryID  string `json:"recoveryId"`
			ID          string `json:"id"`
			DeletedDate int64  `json:"deletedDate"`
		} `json:"value"`
		NextLink string `json:"nextLink"`
	}
	if err := common.Unmarshal(body, &page); err != nil {
		return nil, "", err
	}
	items := make([]deletedSecretInfo, 0, len(page.Value))
	for _, v := range page.Value {
		name := lastPathSegment(v.RecoveryID)
		if name == "" {
			name = lastPathSegment(v.ID)
		}
		if name == "" {
			continue
		}
		items = append(items, deletedSecretInfo{name: name, deletedDate: v.DeletedDate})
	}
	return items, strings.TrimSpace(page.NextLink), nil
}

func lastPathSegment(raw string) string {
	raw = strings.TrimSpace(raw)
	if raw == "" {
		return ""
	}
	if u, err := url.Parse(raw); err == nil && u.Path != "" {
		raw = u.Path
	}
	raw = strings.Trim(raw, "/")
	if i := strings.LastIndex(raw, "/"); i >= 0 {
		raw = raw[i+1:]
	}
	return raw
}

// secretExpired reports whether a secret soft-deleted at deletedDate (unix sec)
// is at or past retentionDays old relative to nowUnix. Pure (testable).
func secretExpired(deletedDate int64, retentionDays int, nowUnix int64) bool {
	if deletedDate <= 0 || retentionDays <= 0 {
		return false
	}
	return nowUnix-deletedDate >= int64(retentionDays)*86400
}

// listDeletedSecrets returns every soft-deleted secret in the vault (paginated).
func (s secretStoreClient) listDeletedSecrets() ([]deletedSecretInfo, error) {
	token, err := s.accessToken()
	if err != nil {
		return nil, err
	}
	endpoint := fmt.Sprintf("%s/deletedsecrets?api-version=7.4", s.vaultURL)
	var out []deletedSecretInfo
	for endpoint != "" {
		req, rErr := http.NewRequest(http.MethodGet, endpoint, nil)
		if rErr != nil {
			return nil, rErr
		}
		req.Header.Set("Authorization", "Bearer "+token)
		resp, dErr := s.client.Do(req)
		if dErr != nil {
			return nil, dErr
		}
		body, _ := io.ReadAll(io.LimitReader(resp.Body, 4<<20))
		resp.Body.Close()
		if resp.StatusCode < http.StatusOK || resp.StatusCode >= http.StatusMultipleChoices {
			message := readSecretStoreError(bytes.NewReader(body))
			if message == "" {
				message = resp.Status
			}
			return nil, fmt.Errorf("Azure Key Vault list deleted secrets failed: %s", message)
		}
		items, next, pErr := parseDeletedSecretsPage(body)
		if pErr != nil {
			return nil, pErr
		}
		out = append(out, items...)
		endpoint = next
	}
	return out, nil
}

// purgeExpiredVaultSecrets permanently purges every soft-deleted vault secret
// older than retentionDays. An optional namePrefix restricts purging to secrets
// HM manages (empty = all soft-deleted secrets in the vault). Returns (purged,
// scanned). Purge-protected vaults safely no-op (purgeSecret treats 403 as ok).
func purgeExpiredVaultSecrets(retentionDays int, namePrefix string, nowUnix int64) (purged int, scanned int, err error) {
	store, err := newSecretStoreClientFromEnv()
	if err != nil {
		return 0, 0, err
	}
	items, err := store.listDeletedSecrets()
	if err != nil {
		return 0, 0, err
	}
	prefix := strings.TrimSpace(namePrefix)
	for _, it := range items {
		if prefix != "" && !strings.HasPrefix(it.name, prefix) {
			continue
		}
		scanned++
		if !secretExpired(it.deletedDate, retentionDays, nowUnix) {
			continue
		}
		if pErr := store.purgeSecret(store.secretRef(it.name)); pErr != nil {
			common.SysLog(fmt.Sprintf("purgeExpiredVaultSecrets: purge %q failed: %s", it.name, pErr.Error()))
			continue
		}
		common.SysLog(fmt.Sprintf("purgeExpiredVaultSecrets: purged %q (soft-deleted %d days ago)", it.name, (nowUnix-it.deletedDate)/86400))
		purged++
	}
	return purged, scanned, nil
}

var secretPurgeTaskOnce sync.Once

// StartSecretPurgeTask launches the daily background purge of vault secrets that
// have been soft-deleted ≥ HEICODE_SECRET_PURGE_RETENTION_DAYS (default 30) ago,
// satisfying issue #4's "render unrecoverable within 30 days" requirement.
// Disabled by HEICODE_SECRET_PURGE_ENABLED=false; no-ops when no vault is
// configured. HEICODE_SECRET_PURGE_NAME_PREFIX scopes purging to HM-managed
// secrets when the vault is shared.
func StartSecretPurgeTask() {
	secretPurgeTaskOnce.Do(func() {
		if !common.GetEnvOrDefaultBool("HEICODE_SECRET_PURGE_ENABLED", true) {
			common.SysLog("secret purge task disabled (HEICODE_SECRET_PURGE_ENABLED=false)")
			return
		}
		if strings.TrimSpace(os.Getenv("AZURE_KEY_VAULT_URL")) == "" {
			return // no vault configured — nothing to purge
		}
		// #33: a destructive purge that scans the WHOLE vault is only safe when
		// HM owns the vault exclusively. If no name prefix scopes purging to
		// HM-managed secrets, require an explicit opt-in (HEICODE_SECRET_PURGE_
		// VAULT_EXCLUSIVE=true) so HM never permanently purges another tenant's
		// soft-deleted secrets that happen to live in a shared vault.
		purgePrefix := strings.TrimSpace(common.GetEnvOrDefaultString("HEICODE_SECRET_PURGE_NAME_PREFIX", ""))
		vaultExclusive := common.GetEnvOrDefaultBool("HEICODE_SECRET_PURGE_VAULT_EXCLUSIVE", false)
		allowed, scopeDesc := secretPurgeScopeAllowed(purgePrefix, vaultExclusive)
		if !allowed {
			common.SysLog("secret purge task NOT started: " + scopeDesc)
			return
		}
		common.SysLog("secret purge scope: " + scopeDesc)
		intervalHours := common.GetEnvOrDefault("HEICODE_SECRET_PURGE_INTERVAL_HOURS", 24)
		if intervalHours < 1 {
			intervalHours = 24
		}
		go func() {
			time.Sleep(5 * time.Minute) // avoid startup churn
			runSecretPurgeOnce()
			ticker := time.NewTicker(time.Duration(intervalHours) * time.Hour)
			defer ticker.Stop()
			for range ticker.C {
				runSecretPurgeOnce()
			}
		}()
		common.SysLog(fmt.Sprintf("secret purge task started: retention=%dd interval=%dh", secretPurgeRetentionDays(), intervalHours))
	})
}

// secretPurgeScopeAllowed decides whether the destructive vault purge may run,
// given the configured name prefix and the vault-exclusive opt-in (#33). A purge
// that scans the WHOLE vault (empty prefix) is only safe when HM owns the vault
// exclusively, so it must be explicitly opted in. Returns the decision plus a
// human-readable scope/refusal description for the startup log. Pure helper for
// unit testing without touching process env.
func secretPurgeScopeAllowed(namePrefix string, vaultExclusive bool) (bool, string) {
	prefix := strings.TrimSpace(namePrefix)
	if prefix == "" {
		if !vaultExclusive {
			return false, "HEICODE_SECRET_PURGE_NAME_PREFIX is empty and HEICODE_SECRET_PURGE_VAULT_EXCLUSIVE!=true — refusing to purge an entire (possibly shared) vault. Set a name prefix to scope to HM-managed secrets, or set HEICODE_SECRET_PURGE_VAULT_EXCLUSIVE=true only if this vault is exclusive to HM."
		}
		return true, "ENTIRE vault (HEICODE_SECRET_PURGE_VAULT_EXCLUSIVE=true, no name prefix)"
	}
	return true, "secrets with name prefix '" + prefix + "'"
}

func secretPurgeRetentionDays() int {
	d := common.GetEnvOrDefault("HEICODE_SECRET_PURGE_RETENTION_DAYS", 30)
	if d < 1 {
		d = 30
	}
	return d
}

func runSecretPurgeOnce() {
	defer func() {
		if r := recover(); r != nil {
			common.SysLog(fmt.Sprintf("secret purge task panic recovered: %v", r))
		}
	}()
	prefix := common.GetEnvOrDefaultString("HEICODE_SECRET_PURGE_NAME_PREFIX", "")
	purged, scanned, err := purgeExpiredVaultSecrets(secretPurgeRetentionDays(), prefix, time.Now().Unix())
	if err != nil {
		common.SysLog("secret purge task: " + err.Error())
		return
	}
	if purged > 0 {
		common.SysLog(fmt.Sprintf("secret purge task: purged %d of %d scanned deleted secrets past %d-day retention", purged, scanned, secretPurgeRetentionDays()))
	}
}