package controller

import (
	"encoding/json"
	"io"
	"net/http"
	"strings"

	"github.com/gin-gonic/gin"

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

// Client error-telemetry ingest (issue #24). Contract: winos#23
// docs/integration/telemetry-ingest-endpoint.md. Body is a TOP-LEVEL JSON array
// of events (NOT wrapped). Auth reuses device-pairing (UserOrV2DeviceAuth). It
// is diagnostic traffic: NEVER bills (separate table, no consume log / quota).
//
// Default-OFF: until the privacy policy discloses account-linkable device IDs
// and endpoint delivery is agreed, HEICODE_TELEMETRY_ENABLED stays false and the
// endpoint answers 410 (kill switch) so the client stops sending.

const (
	telemetryMaxBatch    = 20
	telemetryMaxBodySize = 256 * 1024
	headerDeviceID       = "X-Heicode-Device-Id"
	// Per-field hard cap after redaction (#32): a backstop so a single event
	// can't park an unbounded blob in the telemetry store even within batch
	// limits. stack_top / context are truncated past this many bytes.
	telemetryMaxFieldBytes = 8 * 1024
)

// telemetryContextAllowedKeys whitelists the non-content diagnostic keys the
// client may attach to an event's `context` (#32). Anything else is dropped
// before persistence, so a client regression can't land arbitrary — possibly
// identifying — JSON (prompts, code, tokens, emails, full file paths, raw IPs)
// in the telemetry store. Keep in sync with the client telemetry contract
// (winos#23) and docs/integration/heicode-desktop-client-api.md. Additions must
// be reviewed against the "no identifying content" rule in issue #32.
var telemetryContextAllowedKeys = map[string]bool{
	"route":       true, // logical UI route, e.g. "chat" (no params)
	"retryable":   true, // bool
	"phase":       true, // lifecycle phase enum
	"exit_code":   true, // process exit code (int)
	"duration_ms": true, // numeric timing
	"attempt":     true, // retry attempt count
}

// filterTelemetryContext keeps only whitelisted keys from the client-supplied
// context object, then redacts and size-caps the result (#32). Returns "" when
// the context is empty, unparseable, or has no allowed keys — telemetry is
// best-effort diagnostics, so dropping an unrecognized payload is preferable to
// storing arbitrary JSON.
func filterTelemetryContext(raw json.RawMessage) string {
	if len(raw) == 0 {
		return ""
	}
	var obj map[string]json.RawMessage
	if err := common.Unmarshal(raw, &obj); err != nil {
		return "" // not an object (or malformed) -> drop
	}
	filtered := make(map[string]json.RawMessage, len(obj))
	for k, v := range obj {
		if telemetryContextAllowedKeys[k] {
			filtered[k] = v
		}
	}
	if len(filtered) == 0 {
		return ""
	}
	b, err := common.Marshal(filtered)
	if err != nil {
		return ""
	}
	return capTelemetryField(model.RedactText(string(b)))
}

// capTelemetryField truncates an already-redacted field to telemetryMaxFieldBytes.
func capTelemetryField(s string) string {
	if len(s) <= telemetryMaxFieldBytes {
		return s
	}
	return s[:telemetryMaxFieldBytes]
}

type telemetryEventIn struct {
	ClientId         string          `json:"client_id"`
	SchemaVersion    int             `json:"schema_version"`
	AppVersion       string          `json:"app_version"`
	Platform         string          `json:"platform"`
	OsVersion        string          `json:"os_version"`
	Arch             string          `json:"arch"`
	Locale           string          `json:"locale"`
	ErrorCategory    string          `json:"error_category"`
	ErrorCode        string          `json:"error_code"`
	ErrorMessageHash string          `json:"error_message_hash"`
	StackHash        string          `json:"stack_hash"`
	StackTop         []string        `json:"stack_top"`
	Context          json.RawMessage `json:"context"`
	Timestamp        string          `json:"timestamp"`
	SessionSeq       int             `json:"session_seq"`
}

// parseTelemetryBatch unmarshals the top-level JSON array of events. Pure.
func parseTelemetryBatch(body []byte) ([]telemetryEventIn, error) {
	var events []telemetryEventIn
	if err := common.Unmarshal(body, &events); err != nil {
		return nil, err
	}
	return events, nil
}

// toModel maps an ingested event to its row. Deliberately tolerant (maximize
// capture): unknown enums / sentinel app_version / missing fields are stored
// as-is; schema_version defaults to 1; stack_top/context are kept as JSON text.
func (e telemetryEventIn) toModel(userID int, deviceID string, now int64) model.TelemetryEvent {
	clientID := strings.TrimSpace(e.ClientId)
	if clientID == "" {
		clientID = deviceID
	}
	sv := e.SchemaVersion
	if sv <= 0 {
		sv = 1
	}
	// Defense-in-depth (#24 review): the client already sanitizes, but we also
	// redact stack_top / context server-side — strip sk-/Bearer/URL tokens/JSON
	// secret fields before persistence, so a producer bug can't land plaintext
	// secrets in the telemetry store.
	stackTopJSON := ""
	if len(e.StackTop) > 0 {
		if b, err := common.Marshal(e.StackTop); err == nil {
			stackTopJSON = capTelemetryField(model.RedactText(string(b)))
		}
	}
	// #32: context is restricted to a key whitelist (drop arbitrary/identifying
	// JSON), then redacted and size-capped.
	ctxJSON := filterTelemetryContext(e.Context)
	return model.TelemetryEvent{
		ReceivedAt:       now,
		UserId:           userID,
		ClientId:         clientID,
		SchemaVersion:    sv,
		AppVersion:       e.AppVersion,
		Platform:         e.Platform,
		OsVersion:        e.OsVersion,
		Arch:             e.Arch,
		Locale:           e.Locale,
		ErrorCategory:    e.ErrorCategory,
		ErrorCode:        e.ErrorCode,
		ErrorMessageHash: e.ErrorMessageHash,
		StackHash:        e.StackHash,
		StackTopJSON:     stackTopJSON,
		ContextJSON:      ctxJSON,
		EventTimestamp:   e.Timestamp,
		SessionSeq:       e.SessionSeq,
	}
}

// HeicodeTelemetryEvents: POST /api/heicode/telemetry/events (issue #24).
func HeicodeTelemetryEvents(c *gin.Context) {
	// Kill switch / not-live gate (default OFF). 410 => client stops sending.
	if !common.GetEnvOrDefaultBool("HEICODE_TELEMETRY_ENABLED", false) {
		c.JSON(http.StatusGone, gin.H{"success": false, "message": "telemetry ingest disabled"})
		return
	}
	userID := c.GetInt("id")
	if userID <= 0 {
		c.JSON(http.StatusUnauthorized, gin.H{"success": false, "message": "authentication required"})
		return
	}
	deviceID := strings.TrimSpace(c.GetHeader(headerDeviceID))
	if deviceID == "" {
		// Telemetry is desktop-only (device-paired); reject session-only callers.
		c.JSON(http.StatusForbidden, gin.H{"success": false, "message": "telemetry requires a paired device"})
		return
	}
	body, _ := io.ReadAll(io.LimitReader(c.Request.Body, telemetryMaxBodySize+1))
	if len(body) > telemetryMaxBodySize {
		c.JSON(http.StatusRequestEntityTooLarge, gin.H{"success": false, "message": "telemetry batch too large"})
		return
	}
	events, err := parseTelemetryBatch(body)
	if err != nil {
		c.JSON(http.StatusBadRequest, gin.H{"success": false, "message": "invalid telemetry body (expect a JSON array of events)"})
		return
	}
	if len(events) == 0 {
		c.JSON(http.StatusOK, gin.H{"success": true, "accepted": 0})
		return
	}
	if len(events) > telemetryMaxBatch {
		c.JSON(http.StatusRequestEntityTooLarge, gin.H{"success": false, "message": "telemetry batch exceeds 20 events"})
		return
	}
	now := common.GetTimestamp()
	rows := make([]model.TelemetryEvent, 0, len(events))
	for _, e := range events {
		// Anti-spoof: a present client_id must equal the verified paired device.
		if cid := strings.TrimSpace(e.ClientId); cid != "" && cid != deviceID {
			c.JSON(http.StatusForbidden, gin.H{"success": false, "message": "client_id does not match paired device"})
			return
		}
		rows = append(rows, e.toModel(userID, deviceID, now))
	}
	if err := model.InsertTelemetryEvents(rows); err != nil {
		common.SysLog("telemetry ingest persist failed: " + err.Error())
		c.JSON(http.StatusInternalServerError, gin.H{"success": false, "message": "telemetry persist failed"})
		return
	}
	c.JSON(http.StatusOK, gin.H{"success": true, "accepted": len(rows)})
}