package notify

import (
	"fmt"
	"go/ast"
	"go/parser"
	"go/token"
	"io/fs"
	"path/filepath"
	"sort"
	"strconv"
	"strings"
	"testing"
)

// R-329 — the hub's severity vocabulary, pinned by an AST walk over the WHOLE controller.
//
// THE DEFECT THIS EXISTS TO KILL. `NotifyAppStartFailures` emitted severity `"warn"`. The hub accepts
// only {info, warning, error, critical} and **silently coerces** anything else to `info` at ingest,
// after which `severityNotifies` drops it and NEITHER the operator nor the customer leg runs. So the
// dashboard showed the app down, the hub stored the event, and no mail left the building.
//
// **This is the SECOND time.** `DiskAlertKind.Severity`'s own doc comment records that it emitted
// `"warn"` until v0.215.0, and that every Figyelmeztetés-level disk alert the product ever produced
// was delivered to nobody. A comment recorded the lesson; nothing enforced it; it happened again.
// **A comment is not a guard** — this is the guard.
//
// THE LAYER. This sits at the EMITTER, which is where the defect lives: the hub's coercion is
// deliberate and correct (a lost alarm is worse than a mis-routed one), so nothing downstream can
// detect a bad word — by design, the bad word ceases to exist at the hub's front door. The only
// place the mistake is still visible is where it is written.
//
// WHY AN AST WALK AND NOT grep. `strings.Contains` over source cannot tell an emitted severity from
// the word "warn" in a comment, a healthcheck status vocabulary (`internal/monitor`,
// `internal/selftest` both legitimately use "warn"), or a `case "warn":` in an unrelated switch. The
// 2026-08-23 sweep found nine such hits and exactly one real defect.
//
// RED-PROOF (observed, see REPORT.md): put `"warn"` back at notifier.go's app_start_failed emit and
// this fails naming the file, line, call and value.

// hubSeverityVocabulary is the hub's set, verbatim. Sources, both named so a reader can check rather
// than trust: felhom.eu/hub/internal/api/handler.go (the ingest switch) and
// felhom.eu/hub/internal/notify/dispatcher.go (severityNotifies).
var hubSeverityVocabulary = map[string]bool{
	"info": true, "warning": true, "error": true, "critical": true,
}

// severityArg names the functions that take a hub severity, and which argument it is.
var severityArg = map[string]int{
	"emit":      1, // (eventType, severity, message, details)
	"PushEvent": 1, // (eventType, severity, message, details)
	// v0.256.0 (R-558): the key-based producers. Registered here in the SAME commit that introduced
	// them — the walk finds severities by FUNCTION NAME, so a new push helper that is not listed is
	// a set of call sites this contract silently stops checking. It caught its own omission: the
	// conversion moved two dynamic sites off PushEvent and the register immediately reported them as
	// no longer existing, which is the "a stale register entry is also a failure" half doing its job.
	"pushEventMsg":       1, // (eventType, severity, key, details, args...)
	"pushEventMsgSuffix": 1, // (eventType, severity, key, suffix, details, args...)
	"pushEventBoth":      1, // (eventType, severity, message, messageCustomer, details)
}

// knownDynamicSeveritySites are the call sites that pass a VARIABLE rather than a literal, so this
// walk cannot check their value. Each was traced by hand on 2026-08-23 and every reachable value was
// in the vocabulary. **They are listed so that a NEW dynamic site cannot appear unnoticed** — the
// honest limit of an AST check is that it cannot follow a variable, and an unlisted limit is not a
// limit, it is a hole.
var knownDynamicSeveritySites = map[string]string{
	"internal/notify/notifier.go:emit": `pass-through of its own severity parameter to PushEvent — the value is checked at emit's CALLERS, above`,
	// v0.256.0 (R-558): three more pass-throughs, the same shape as emit. Each forwards its OWN
	// severity parameter to pushEventBoth without inspecting it, so the value is checked at their
	// callers — which is where the walk's 36 literals are found.
	"internal/notify/notifier.go:PushEvent":                `pass-through of its own severity parameter to pushEventBoth — checked at PushEvent's callers`,
	"internal/notify/notifier.go:pushEventMsg":             `pass-through of its own severity parameter to pushEventBoth — checked at pushEventMsg's callers`,
	"internal/notify/notifier.go:pushEventMsgSuffix":       `pass-through of its own severity parameter to pushEventBoth — checked at pushEventMsgSuffix's callers`,
	"internal/notify/notifier.go:NotifyControllerUpdated":  `local var: "info", or "error" when the update failed`,
	"internal/notify/notifier.go:NotifyDRCompleted":        `local var: "info", or "warning" when failCount > 0`,
	"internal/notify/notifier.go:NotifyAgentChannelDown":   `internal/channelhealth's classifier — every severity literal in checker.go is "warning" or "error"`,
	"internal/notify/notifier.go:NotifyDiskHealthDegraded": `DiskAlertKind.Severity() — pinned behaviourally by TestR329_DiskAlertSeveritiesStillSatisfyTheContract`,
	"cmd/controller/main.go:main":                          `fillwatch.Band.Severity() in the SetNotify closure — pinned by TestR329_FillwatchNeverEmitsTheEmptySeverity`,
}

func walkControllerFiles(t *testing.T, fn func(path string, fset *token.FileSet, f *ast.File)) {
	t.Helper()
	root, err := filepath.Abs("../..") // the controller module root
	if err != nil {
		t.Fatal(err)
	}
	fset := token.NewFileSet()
	err = filepath.WalkDir(root, func(path string, d fs.DirEntry, err error) error {
		if err != nil {
			return err
		}
		if d.IsDir() {
			if d.Name() == "vendor" || d.Name() == ".git" || d.Name() == "node_modules" {
				return filepath.SkipDir
			}
			return nil
		}
		if !strings.HasSuffix(path, ".go") || strings.HasSuffix(path, "_test.go") {
			return nil
		}
		f, perr := parser.ParseFile(fset, path, nil, parser.ParseComments)
		if perr != nil {
			return fmt.Errorf("parse %s: %w", path, perr)
		}
		rel, _ := filepath.Rel(root, path)
		fn(rel, fset, f)
		return nil
	})
	if err != nil {
		t.Fatal(err)
	}
}

// calleeName returns the bare function name for `foo(...)` and `x.foo(...)`.
func calleeName(call *ast.CallExpr) string {
	switch fn := call.Fun.(type) {
	case *ast.Ident:
		return fn.Name
	case *ast.SelectorExpr:
		return fn.Sel.Name
	}
	return ""
}

func TestR329_EveryEmittedSeverityIsInTheHubVocabulary(t *testing.T) {
	var checked int
	var dynamic []string

	walkControllerFiles(t, func(rel string, fset *token.FileSet, f *ast.File) {
		// Attribute each call to the FuncDecl that encloses it, by walking declarations rather than
		// trusting Inspect's visit order — a closure inside main() must read as "main", and a call in
		// a var block must not inherit the previous function's name.
		for _, decl := range f.Decls {
			fd, isFunc := decl.(*ast.FuncDecl)
			enclosing := "(file scope)"
			var scope ast.Node = decl
			if isFunc {
				enclosing = fd.Name.Name
				scope = fd
			}
			inspectForSeverity(t, rel, enclosing, scope, fset, &checked, &dynamic)
		}
	})

	// The walk must actually have found call sites — a guard that silently examines nothing is the
	// "instrument that can drop results" failure, and it would pass forever.
	if checked < 15 {
		t.Fatalf("only %d severity literals examined — the AST walk is not reaching the call sites; "+
			"fix this test before trusting a green from it", checked)
	}
	t.Logf("checked %d severity literals across the controller", checked)

	// The dynamic sites are a stated limit, and the list is the mechanism that keeps it stated.
	sort.Strings(dynamic)
	seen := map[string]bool{}
	for _, d := range dynamic {
		if seen[d] {
			continue
		}
		seen[d] = true
		if _, known := knownDynamicSeveritySites[d]; !known {
			t.Errorf("NEW dynamic severity call site %q — this walk cannot check a variable's value. "+
				"Trace every value it can take; if all are in the hub vocabulary, add it to "+
				"knownDynamicSeveritySites with the reason. Do not delete this check.", d)
		}
	}
	for known := range knownDynamicSeveritySites {
		if !seen[known] {
			t.Errorf("registered dynamic site %q no longer exists — remove it from "+
				"knownDynamicSeveritySites so the register stays honest", known)
		}
	}
}

// The vocabulary itself must match the hub's, and DiskAlertKind.Severity — the function whose doc
// comment records the first occurrence — must still satisfy it.
func TestR329_DiskAlertSeveritiesStillSatisfyTheContract(t *testing.T) {
	for _, k := range []DiskAlertKind{
		DiskAlertWarn, DiskAlertFailSelfReported, DiskAlertFailSectors,
		DiskAlertFailTemperature, DiskAlertFailWorsened,
	} {
		if got := k.Severity(); !hubSeverityVocabulary[got] {
			t.Errorf("DiskAlertKind(%d).Severity() = %q, not in the hub vocabulary", k, got)
		}
	}
	// And the one that regressed: a warning must be a *warning*, not "warn" and not "info".
	if got := DiskAlertWarn.Severity(); got != "warning" {
		t.Errorf("DiskAlertWarn.Severity() = %q, want \"warning\"", got)
	}
}

// inspectForSeverity checks every severity-taking call inside one declaration.
func inspectForSeverity(t *testing.T, rel, enclosing string, scope ast.Node, fset *token.FileSet, checked *int, dynamic *[]string) {
	t.Helper()
	ast.Inspect(scope, func(n ast.Node) bool {
		call, ok := n.(*ast.CallExpr)
		if !ok {
			return true
		}
		idx, wanted := severityArg[calleeName(call)]
		if !wanted || len(call.Args) <= idx {
			return true
		}
		lit, isLit := call.Args[idx].(*ast.BasicLit)
		if !isLit || lit.Kind != token.STRING {
			*dynamic = append(*dynamic, rel+":"+enclosing)
			return true
		}
		val, err := strconv.Unquote(lit.Value)
		if err != nil {
			t.Errorf("%s: unparseable severity literal %s", fset.Position(lit.Pos()), lit.Value)
			return true
		}
		*checked++
		if !hubSeverityVocabulary[val] {
			t.Errorf("%s: %s(...) emits severity %q, which is NOT in the hub's vocabulary "+
				"{info, warning, error, critical}.\n"+
				"    The hub COERCES it to \"info\" at ingest, SILENTLY, and severityNotifies then "+
				"drops \"info\" — so this event is stored and emailed to NOBODY, on either leg.\n"+
				"    This exact mistake shipped once before (DiskAlertKind.Severity, fixed v0.215.0).",
				fset.Position(lit.Pos()), calleeName(call), val)
		}
		return true
	})
}