package pipeline

import (
	"go/ast"
	"go/parser"
	"go/token"
	"os"
	"strconv"
	"strings"
	"testing"
)

// flagseverity_test.go pins the chapter passport's "worst flag" ranking.
//
// ⚠ WHY THIS FILE EXISTS AT ALL. flagReasonSeverity had no test of any kind, and the shape of the bug it
// carried is the one this project keeps meeting: a hand-written list that stopped tracking the constants it
// lists. `off_target_lang` — the flag an entire pack was built to raise — was never added to the switch, so
// it fell to the default and became the MOST BENIGN reason in the passport, below `length`. A chapter that
// came back in the wrong language reported «length» as its worst problem. Nothing was wrong with the code;
// the list was simply not tied to anything.

// TestEveryFlagReasonIsRanked reads the FlagReason constants OUT OF THE SOURCE rather than retyping them
// here, because a hand-written list in the test would rot exactly like the hand-written list in the code —
// and would then certify the rot. This is the guarantee that the next flag someone adds cannot land in the
// unknown bucket silently: it fails here on the day it is declared, not on the day it is misreported.
func TestEveryFlagReasonIsRanked(t *testing.T) {
	// ⚠ EVERY FILE OF THE PACKAGE, not disposition.go alone — the first version of this test named one
	// file, and a planting that declared a FlagReason anywhere else walked straight past it while the test
	// still reported «every declared reason is ranked». The guarantee was one file narrower than its own
	// sentence, which is the defect class this file exists to prevent, committed by the file itself.
	entries, err := os.ReadDir(".")
	if err != nil {
		t.Fatalf("read the package directory: %v", err)
	}
	var sources []string
	for _, e := range entries {
		n := e.Name()
		if e.IsDir() || !strings.HasSuffix(n, ".go") || strings.HasSuffix(n, "_test.go") {
			continue
		}
		sources = append(sources, n)
	}
	if len(sources) < 10 {
		t.Fatalf("only %d source files found — the walk stopped seeing the package: %v", len(sources), sources)
	}
	fset := token.NewFileSet()
	var decls []ast.Decl
	for _, name := range sources {
		f, perr := parser.ParseFile(fset, name, nil, 0)
		if perr != nil {
			t.Fatalf("parse %s: %v", name, perr)
		}
		decls = append(decls, f.Decls...)
	}
	var found int
	for _, d := range decls {
		gd, ok := d.(*ast.GenDecl)
		if !ok || gd.Tok != token.CONST {
			continue
		}
		for _, sp := range gd.Specs {
			vs, ok := sp.(*ast.ValueSpec)
			if !ok {
				continue
			}
			// ⚠ THE TYPE MUST BE WRITTEN ON THIS SPEC. An earlier version carried the previous spec's type
			// forward, which is not how Go types a const block: a spec that has a VALUE and no type is its
			// own UNTYPED constant and inherits nothing. That version raised a FALSE ALARM — an ordinary
			// string constant placed after a FlagReason spec in the same block was accused of being an
			// unranked flag, and a doc-URL constant would have failed this test with a message about the
			// chapter passport. A test that accuses the innocent is not enforcing its own sentence, and this
			// one exists to say what IS a declared reason.
			//
			// ⚠ AND BOTH GO SPELLINGS COUNT. `X FlagReason = "…"` writes the type in the spec; the equally
			// ordinary `X = FlagReason("…")` writes it as a CONVERSION, leaving vs.Type nil — and a walk
			// that looked only at vs.Type was blind to it, which an adversarial pass exhibited as a pair:
			// the typed spelling of one declaration RED, the conversion spelling of the same declaration
			// SURVIVED. The sentence that used to stand here — «a missed declaration would trip the found
			// floor rather than pass silently» — was simply false: one missing constant leaves the count at
			// 16 against a floor of 15, and nothing trips.
			if len(vs.Values) == 0 {
				continue
			}
			var lit *ast.BasicLit
			switch {
			case isFlagReasonIdent(vs.Type):
				lit, _ = vs.Values[0].(*ast.BasicLit)
			default:
				call, isCall := vs.Values[0].(*ast.CallExpr)
				if !isCall || !isFlagReasonIdent(call.Fun) || len(call.Args) != 1 {
					continue
				}
				lit, _ = call.Args[0].(*ast.BasicLit)
			}
			if lit == nil || lit.Kind != token.STRING {
				continue
			}
			val, err := strconv.Unquote(lit.Value)
			if err != nil {
				t.Fatalf("%s: %v", vs.Names[0].Name, err)
			}
			if val == "" {
				continue // reasonOK — the sentinel for "not a flag", deliberately unranked
			}
			found++
			if _, ranked := flagSeverity[FlagReason(val)]; !ranked {
				t.Errorf("%s (%q) has no entry in flagSeverity: it would rank %d — BELOW every real diagnosis, "+
					"so it can never be reported as a chapter's worst flag", vs.Names[0].Name, val, severityUnknown)
			}
		}
	}
	// The reader of this test must know it actually read something: a parse that silently matched nothing
	// would pass forever and guard nothing — the same failure class one layer up.
	if found < 15 {
		t.Fatalf("only %d FlagReason constants were read out of the package's %d source files — the walk "+
			"stopped matching the source, and this test is no longer checking anything", found, len(sources))
	}
	if len(flagSeverity) != found {
		t.Errorf("flagSeverity has %d entries for %d declared reasons — a rank exists for a reason that no "+
			"longer does", len(flagSeverity), found)
	}
}

// TestOffTargetLangIsRankedWithTheContentFailures is the specific harm, asserted as a number and not as a
// membership: the flag must out-rank the budget symptoms, because those are what it was losing to.
func TestOffTargetLangIsRankedWithTheContentFailures(t *testing.T) {
	off := flagReasonSeverity(string(FlagOffTargetLang))
	if off == severityUnknown {
		t.Fatal("off_target_lang fell to the unknown bucket — the exact defect this file was written for")
	}
	for _, milder := range []FlagReason{FlagLength, FlagEmpty, FlagGlossaryMiss, FlagSanitizerStripped} {
		if off >= flagReasonSeverity(string(milder)) {
			t.Errorf("off_target_lang (%d) must be WORSE than %s (%d): a chapter in the wrong language is not "+
				"a budget symptom", off, milder, flagReasonSeverity(string(milder)))
		}
	}
	// It is a content failure, ranked with the echo it sits beside in the classifier.
	if off != flagReasonSeverity(string(FlagCJKArtifact)) {
		t.Errorf("off_target_lang (%d) and cjk_artifact (%d) are the same class — «the output is not a "+
			"translation of this text into the asked-for language» — and must rank together",
			off, flagReasonSeverity(string(FlagCJKArtifact)))
	}
	// A refusal still outranks both: the provider said no, which is a different and worse fact.
	if off <= flagReasonSeverity(string(FlagHardRefusal)) {
		t.Error("a hard refusal must still outrank an off-target completion")
	}
}

// isFlagReasonIdent reports whether an expression names the FlagReason type — as a spec's type or as the
// function of a conversion. One helper for both spellings, so the walk cannot learn one and forget the other.
func isFlagReasonIdent(e ast.Expr) bool {
	id, ok := e.(*ast.Ident)
	return ok && id.Name == "FlagReason"
}