package pipeline

import (
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"testing"

	"textmachine/backend/internal/config"
)

// promptlabel_test.go: `prompt_version` must track the BYTES of the prompt it labels.
//
// WHY THIS IS A GATE AND NOT A NORM. The norm already exists, written into the shipping config itself —
// pipeline-c2.yaml: «лейбл обязан следовать за новым SHA файла» — and it was broken anyway:
// prompts/zh-ru/editor.md was edited on 2026-08-01 while prompt_version stayed v3-discourse-reflow. The
// cold run of 31.08 then nearly built a causal conclusion on comparing itself against a July bench
// carrying that same label. Money was never at risk (PromptSHA256 folds into the snapshot, so the ENGINE
// always knew); what was at risk is the COMPARABILITY of two runs, which is what an experiment is made of.
// A rule that lives only in a comment inside a ratified decision, and is then skipped by the next ratified
// decision, is a rule that needs a machine.
//
// WHY A REPO GATE AND NOT A RUNTIME CHECK. A runtime check can only compare a label against the payloads
// THIS project database happens to hold, so it catches a label reused within one book. The incident was
// BETWEEN books — a bench project and a fresh one, different databases — which is exactly the case a
// runtime check cannot see. The repository is where both live, so the repository is where the pair is
// pinned. It is also $0, snapshot-neutral, and it fails at CI time rather than after a purchase.
//
// UPDATING IT IS THE POINT, NOT AN OBSTACLE: a deliberate prompt edit is expected to come with a new
// label, and `TM_UPDATE_PROMPT_LABELS=1 go test ./internal/pipeline/ -run TestPromptLabelsPinTheirBytes`
// re-writes the ledger — the same shape as TM_UPDATE_GOLDEN. What must never happen silently is the third
// case: the same label over different bytes.

// promptLabelLedger is the checked-in memory: "<pair>/<role>/<label>" → sha256 of the CANONICAL prompt
// (comments stripped — the same form the snapshot folds, so an edited comment costs nobody a re-purchase).
const promptLabelLedger = "testdata/prompt-labels.json"

// shippingPipelines are the configs whose prompts ship. The arms are included because an arm exists to
// isolate ONE variable, and a prompt that moved under a stale label puts a second one in the comparison.
var shippingPipelines = []string{
	"pipeline-c1.yaml", "pipeline-c2.yaml",
	"pipeline-arm-deepseek-pro.yaml", "pipeline-arm-glm.yaml", "pipeline-arm-mistral.yaml",
}

func TestPromptLabelsPinTheirBytes(t *testing.T) {
	models, err := config.LoadModels(filepath.Join("..", "..", "configs", "models.yaml"))
	if err != nil {
		t.Fatalf("load the shipping models.yaml: %v", err)
	}
	const pair = "zh-ru" // the only pair with a prompt pack in the repo; a new pair joins this map by existing
	seen := map[string]string{}
	for _, pf := range shippingPipelines {
		p, err := config.LoadPipeline(filepath.Join("..", "..", "configs", pf), models, pair, nil)
		if err != nil {
			t.Fatalf("load %s: %v", pf, err)
		}
		for _, st := range p.Stages {
			key := fmt.Sprintf("%s/%s/%s", pair, st.Role, st.PromptVersion)
			tpl, err := LoadPromptTemplate(st.PromptPath)
			if err != nil {
				t.Fatalf("%s stage %q: load its resolved prompt %s: %v", pf, st.Name, st.PromptPath, err)
			}
			// A label used by two stages must mean ONE file's bytes, or it is not a label.
			if prev, dup := seen[key]; dup && prev != tpl.SHA256 {
				t.Errorf("label %q names two different prompt bodies across the shipping configs (%s vs %s) — "+
					"a label that is not a function of the bytes cannot make two runs comparable",
					key, prev[:12], tpl.SHA256[:12])
			}
			seen[key] = tpl.SHA256
		}
		// The BANK ROLES resolve their prompts through the gate rather than through a stage, and they are
		// paid calls whose comparability matters exactly as much: the terminologist's consolidation is what
		// a book's bank ends up saying. They carry no prompt_version of their own, so the gate's own
		// version string is the label — which is the honest answer, not a workaround: it is what a run logs
		// as the identity of that contour.
		//
		// ⚠ BOTH bank roles, not one. The classifier was outside this sweep while no shipping config turned
		// it on; backlog row 140 turns it on, and its prompt decides a term's CLASS — which routes a name to
		// transliteration and a realia to a translation. A pass whose class definitions moved under a
		// stationary label is exactly as uncomparable as a render whose instructions did.
		if g := p.Gates.Terminology; g.Enabled {
			for _, role := range []struct{ name, path string }{
				{"terminologist", g.PromptPath},
				{"classifier", g.ClassifyPromptPath},
			} {
				if role.path == "" {
					continue // the phase is off, so it has no prompt and buys nothing
				}
				tpl, err := LoadPromptTemplate(role.path)
				if err != nil {
					t.Fatalf("%s: load the %s prompt %s: %v", pf, role.name, role.path, err)
				}
				seen[fmt.Sprintf("%s/%s/%s", pair, role.name, terminologyVersion)] = tpl.SHA256
			}
		}
	}
	if len(seen) == 0 {
		t.Fatal("no shipping stage resolved a prompt — this gate would be enforcing nothing")
	}

	if os.Getenv("TM_UPDATE_PROMPT_LABELS") == "1" {
		writePromptLedger(t, seen)
		t.Logf("prompt-label ledger re-written with %d entr(ies) — review the diff: a NEW key is a "+
			"deliberate bump, a CHANGED value under an existing key is the defect this gate exists for", len(seen))
		return
	}

	raw, err := os.ReadFile(promptLabelLedger)
	if err != nil {
		t.Fatalf("read the prompt-label ledger (%s): %v — create it with TM_UPDATE_PROMPT_LABELS=1", promptLabelLedger, err)
	}
	var stored map[string]string
	if err := json.Unmarshal(raw, &stored); err != nil {
		t.Fatalf("the prompt-label ledger is not readable JSON: %v", err)
	}
	// ⚠ AN ENTRY NOBODY CLAIMED IS A LOSS, NOT A LEFTOVER, and the sweep could not see one: the loop below
	// walks `seen` and never `stored`, so DROPPING a role from the sweep above left its ledger entry orphaned
	// and its prompt unpinned, with every test green. Found by planting — the classifier line was added to
	// this sweep by the pack that made it ship, and removing it again cost nothing.
	//
	// A legitimately retired label is retired by deleting its line here in the same commit; an orphan means
	// the sweep stopped looking at something it used to watch.
	for _, key := range sortedKeys(stored) {
		if _, claimed := seen[key]; !claimed {
			t.Errorf("the ledger records %q and this run found nothing that uses it — either a shipping config stopped resolving that prompt, or the sweep above stopped covering it. Delete the line deliberately, or restore what dropped out.", key)
		}
	}
	for _, key := range sortedKeys(seen) {
		want, known := stored[key]
		switch {
		case !known:
			t.Errorf("label %q is not in the ledger. If you BUMPED the label deliberately, re-write the "+
				"ledger with TM_UPDATE_PROMPT_LABELS=1 and commit it — that is the whole point. If you did "+
				"not, a stage is quoting a label nobody recorded.", key)
		case want != seen[key]:
			t.Errorf("⚠ THE PROMPT MOVED AND ITS LABEL DID NOT. %q was recorded over sha %s and now resolves "+
				"to %s. Two runs carrying this label are NOT comparable, and nothing else in the repository "+
				"would have said so (prompts/zh-ru/editor.md, 2026-08-01, is this defect's own history). "+
				"Bump prompt_version in the shipping config and re-write the ledger with "+
				"TM_UPDATE_PROMPT_LABELS=1 — or restore the bytes.", key, want[:12], seen[key][:12])
		}
	}
}

func sortedKeys(m map[string]string) []string {
	out := make([]string, 0, len(m))
	for k := range m {
		out = append(out, k)
	}
	sort.Strings(out)
	return out
}

// writePromptLedger renders the ledger deterministically: sorted keys, indented, trailing newline — so a
// re-write produces a diff a human reads rather than a re-ordering.
func writePromptLedger(t *testing.T, seen map[string]string) {
	t.Helper()
	var b strings.Builder
	b.WriteString("{\n")
	keys := sortedKeys(seen)
	for i, k := range keys {
		comma := ","
		if i == len(keys)-1 {
			comma = ""
		}
		fmt.Fprintf(&b, "  %q: %q%s\n", k, seen[k], comma)
	}
	b.WriteString("}\n")
	if err := os.MkdirAll(filepath.Dir(promptLabelLedger), 0o755); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(promptLabelLedger, []byte(b.String()), 0o644); err != nil {
		t.Fatal(err)
	}
}