// Package api: log-scan rule HTTP handlers. The scanner manager
// lives in internal/logscanner; this file is the REST surface that
// lets operators create, edit, and test rules from the UI.
package api

import (
	"errors"
	"log/slog"
	"net/http"
	"regexp"
	"strconv"
	"strings"

	"github.com/go-chi/chi/v5"

	"github.com/alexei/tinyforge/internal/logscanner"
	"github.com/alexei/tinyforge/internal/store"
)

// LogScanReloader is what the API calls after any rule CRUD so the
// scanner manager swaps its snapshot, and what the /stats endpoint
// queries for runtime counters. Implemented by *logscanner.Manager;
// nil-tolerant on the API side so the routes still work in a
// scanner-disabled deployment.
type LogScanReloader interface {
	ReloadRules() error
	Stats() logscanner.Stats
}

// SetLogScanReloader wires the API → manager reload signal. Called
// from main after both subsystems are constructed.
func (s *Server) SetLogScanReloader(r LogScanReloader) {
	s.logScanReloader = r
}

// ruleInput is the JSON shape accepted by POST + PATCH. Pointers
// distinguish "absent" from explicit empty/zero. WorkloadID and
// OverridesID are immutable on update (per store.UpdateLogScanRule)
// so they only appear here for create.
type ruleInput struct {
	WorkloadID      *string `json:"workload_id"`
	OverridesID     *int64  `json:"overrides_id"`
	Name            *string `json:"name"`
	Pattern         *string `json:"pattern"`
	Severity        *string `json:"severity"`
	Streams         *string `json:"streams"`
	CooldownSeconds *int    `json:"cooldown_seconds"`
	Enabled         *bool   `json:"enabled"`
}

// listLogScanRules handles GET /api/log-scan-rules. Optional query
// filter `workload_id=...` returns only rules scoped to that
// workload (workload-only + override rows, NOT globals).
func (s *Server) listLogScanRules(w http.ResponseWriter, r *http.Request) {
	if wlID := r.URL.Query().Get("workload_id"); wlID != "" {
		out, err := s.store.ListLogScanRulesByWorkload(wlID)
		if err != nil {
			respondError(w, http.StatusInternalServerError, "list log scan rules")
			return
		}
		respondJSON(w, http.StatusOK, out)
		return
	}
	out, err := s.store.ListLogScanRules()
	if err != nil {
		respondError(w, http.StatusInternalServerError, "list log scan rules")
		return
	}
	respondJSON(w, http.StatusOK, out)
}

// getLogScanRule handles GET /api/log-scan-rules/{id}.
func (s *Server) getLogScanRule(w http.ResponseWriter, r *http.Request) {
	id, ok := parseRuleID(w, r)
	if !ok {
		return
	}
	rule, err := s.store.GetLogScanRule(id)
	if err != nil {
		mapStoreError(w, err, "log scan rule")
		return
	}
	respondJSON(w, http.StatusOK, rule)
}

// createLogScanRule handles POST /api/log-scan-rules.
func (s *Server) createLogScanRule(w http.ResponseWriter, r *http.Request) {
	var in ruleInput
	if !decodeJSON(w, r, &in) {
		return
	}
	rule := store.LogScanRule{
		WorkloadID:      derefString(in.WorkloadID),
		OverridesID:     derefInt64(in.OverridesID),
		Name:            derefString(in.Name),
		Pattern:         derefString(in.Pattern),
		Severity:        firstNonEmpty(derefString(in.Severity), store.LogScanSeverityWarn),
		Streams:         firstNonEmpty(derefString(in.Streams), store.LogScanStreamAll),
		CooldownSeconds: derefIntDefault(in.CooldownSeconds, 60),
		Enabled:         in.Enabled == nil || *in.Enabled,
	}
	if msg := validateRulePattern(rule.Pattern); msg != "" {
		respondError(w, http.StatusBadRequest, msg)
		return
	}
	out, err := s.store.CreateLogScanRule(rule)
	if err != nil {
		// Store-side validation errors map to 400; anything else
		// (driver errors) is a 500 without leaking the raw text.
		if isClientValidationErr(err) {
			respondError(w, http.StatusBadRequest, err.Error())
			return
		}
		respondError(w, http.StatusInternalServerError, "create log scan rule")
		return
	}
	s.reloadLogScan()
	respondJSON(w, http.StatusCreated, out)
}

// updateLogScanRule handles PATCH /api/log-scan-rules/{id}. Scope
// fields (workload_id, overrides_id) are immutable; pattern/severity/
// streams/cooldown/enabled/name are individually overridable.
func (s *Server) updateLogScanRule(w http.ResponseWriter, r *http.Request) {
	id, ok := parseRuleID(w, r)
	if !ok {
		return
	}
	existing, err := s.store.GetLogScanRule(id)
	if err != nil {
		mapStoreError(w, err, "log scan rule")
		return
	}
	var in ruleInput
	if !decodeJSON(w, r, &in) {
		return
	}
	if in.Name != nil {
		existing.Name = *in.Name
	}
	if in.Pattern != nil {
		existing.Pattern = *in.Pattern
	}
	if in.Severity != nil && *in.Severity != "" {
		existing.Severity = *in.Severity
	}
	if in.Streams != nil && *in.Streams != "" {
		existing.Streams = *in.Streams
	}
	if in.CooldownSeconds != nil {
		existing.CooldownSeconds = *in.CooldownSeconds
	}
	if in.Enabled != nil {
		existing.Enabled = *in.Enabled
	}
	if msg := validateRulePattern(existing.Pattern); msg != "" {
		respondError(w, http.StatusBadRequest, msg)
		return
	}
	out, err := s.store.UpdateLogScanRule(existing)
	if err != nil {
		if errors.Is(err, store.ErrNotFound) {
			respondNotFound(w, "log scan rule")
			return
		}
		if isClientValidationErr(err) {
			respondError(w, http.StatusBadRequest, err.Error())
			return
		}
		respondError(w, http.StatusInternalServerError, "update log scan rule")
		return
	}
	s.reloadLogScan()
	respondJSON(w, http.StatusOK, out)
}

// deleteLogScanRule handles DELETE /api/log-scan-rules/{id}. Override
// rows that reference this id are cascade-deleted by the store layer.
func (s *Server) deleteLogScanRule(w http.ResponseWriter, r *http.Request) {
	id, ok := parseRuleID(w, r)
	if !ok {
		return
	}
	if err := s.store.DeleteLogScanRule(id); err != nil {
		mapStoreError(w, err, "log scan rule")
		return
	}
	s.reloadLogScan()
	w.WriteHeader(http.StatusNoContent)
}

// testLogScanRule handles POST /api/log-scan-rules/{id}/test. Body
// `{"sample_line": "..."}` returns whether the rule pattern matches +
// any captured subgroups. Lets operators iterate on regexes in the
// UI without spinning up real container traffic.
func (s *Server) testLogScanRule(w http.ResponseWriter, r *http.Request) {
	id, ok := parseRuleID(w, r)
	if !ok {
		return
	}
	rule, err := s.store.GetLogScanRule(id)
	if err != nil {
		mapStoreError(w, err, "log scan rule")
		return
	}
	var body struct {
		SampleLine string `json:"sample_line"`
	}
	if !decodeJSON(w, r, &body) {
		return
	}
	respondJSON(w, http.StatusOK, testRuleAgainstLine(rule, body.SampleLine))
}

// getEffectiveLogScanRules handles GET /api/workloads/{id}/effective-rules.
// Returns the resolved effective rule set (globals minus overrides +
// workload-only + override-substitutes) that the scanner uses for
// this workload's containers.
func (s *Server) getEffectiveLogScanRules(w http.ResponseWriter, r *http.Request) {
	workloadID := chi.URLParam(r, "id")
	if workloadID == "" {
		respondError(w, http.StatusBadRequest, "workload id required")
		return
	}
	rules, err := s.store.EffectiveLogScanRules(workloadID)
	if err != nil {
		respondError(w, http.StatusInternalServerError, "compute effective rules")
		return
	}
	respondJSON(w, http.StatusOK, rules)
}

// testResult is the shape returned by /test. Keeping it focused —
// caller wants a yes/no + captures so they can iterate, nothing more.
type ruleTestResult struct {
	Matched  bool              `json:"matched"`
	Captures map[string]string `json:"captures,omitempty"`
	Error    string            `json:"error,omitempty"`
}

func testRuleAgainstLine(rule store.LogScanRule, line string) ruleTestResult {
	re, err := regexp.Compile(rule.Pattern)
	if err != nil {
		return ruleTestResult{Error: "rule pattern is invalid: " + err.Error()}
	}
	subs := re.FindStringSubmatch(line)
	if subs == nil {
		return ruleTestResult{Matched: false}
	}
	captures := map[string]string{}
	names := re.SubexpNames()
	for i, s := range subs[1:] {
		key := names[i+1]
		if key == "" {
			key = "$" + strconv.Itoa(i+1)
		}
		captures[key] = s
	}
	return ruleTestResult{Matched: true, Captures: captures}
}

func validateRulePattern(pattern string) string {
	if strings.TrimSpace(pattern) == "" {
		return "pattern is required"
	}
	if _, err := regexp.Compile(pattern); err != nil {
		return "pattern invalid: " + err.Error()
	}
	return ""
}

// isClientValidationErr returns true when the store error is one of
// the validation errors raised by CreateLogScanRule /
// UpdateLogScanRule (name/pattern required, invalid enum, negative
// cooldown). Used to map those to 400 rather than 500 without
// exposing driver text.
func isClientValidationErr(err error) bool {
	if err == nil {
		return false
	}
	msg := err.Error()
	for _, needle := range []string{
		"name is required",
		"pattern is required",
		"invalid severity",
		"invalid streams",
		"cooldown_seconds must be",
		"override row requires workload_id",
	} {
		if strings.Contains(msg, needle) {
			return true
		}
	}
	return false
}

func parseRuleID(w http.ResponseWriter, r *http.Request) (int64, bool) {
	raw := chi.URLParam(r, "id")
	id, err := strconv.ParseInt(raw, 10, 64)
	if err != nil || id <= 0 {
		respondError(w, http.StatusBadRequest, "invalid rule id")
		return 0, false
	}
	return id, true
}

func derefInt64(p *int64) int64 {
	if p == nil {
		return 0
	}
	return *p
}

func derefIntDefault(p *int, def int) int {
	if p == nil {
		return def
	}
	return *p
}

// getLogScanStats handles GET /api/log-scan-rules/stats. Returns
// engine drop counters + last-snapshot compile errors + active
// tail count so operators can see when their patterns are too
// greedy or syntactically broken. When the scanner manager is not
// wired (scanner-disabled deployment), returns a zero-valued
// shape rather than 404 so the frontend can render the panel
// uniformly.
func (s *Server) getLogScanStats(w http.ResponseWriter, r *http.Request) {
	if s.logScanReloader == nil {
		respondJSON(w, http.StatusOK, logscanner.Stats{})
		return
	}
	respondJSON(w, http.StatusOK, s.logScanReloader.Stats())
}

// reloadLogScan fires the manager's snapshot rebuild. Nil-tolerant
// so the API can run before the manager is wired (and in
// scanner-disabled deployments). Failures are logged at warn —
// we don't fail the originating CRUD request because that already
// succeeded, but operators need a signal so they don't chase a
// "why isn't my rule firing?" mystery.
func (s *Server) reloadLogScan() {
	if s.logScanReloader == nil {
		return
	}
	if err := s.logScanReloader.ReloadRules(); err != nil {
		slog.Warn("log-scan reload failed; manager snapshot may be stale",
			"error", err)
	}
}