package gates

import (
	"fmt"
	"os"
	"path/filepath"
	"regexp"
	"sort"
	"strings"
	"testing"

	"textmachine/platform/internal/httpapi"
	"textmachine/platform/internal/pgstore"
	"textmachine/platform/internal/runner"
)

// canonPath is the ratified API contract, from this package's directory. It is outside the zone on
// purpose: the contract belongs to `docs/` and this zone only serves it.
const canonPath = zoneRoot + "/../docs/architecture/14-api-contract/openapi.yaml"

// The constant a deployment announces itself with must be the version the ratified canon carries.
//
// Every other test of this constant compares the WIRE to the constant, which is self-consistent and
// passes at any value — the class PD-1 names. This is the only check with an independent second
// source, and it is the reason the constant went two ratifications without moving: `0.3.0` was
// served while `0.4.0` was the canon, so a client generated against what the deployment ANNOUNCES
// would have refused the shapes it actually returns (while the major is `0`, a differing minor
// carries breaking changes by design — canon §Versioning).
//
// It reads the canon rather than a copy of the number: a gate that holds a second copy of the fact
// is one more place to forget.
func TestTheAnnouncedContractVersionIsTheOneTheCanonRatified(t *testing.T) {
	src, err := os.ReadFile(filepath.Join(canonPath))
	if err != nil {
		// Not skipped. A missing canon leaves this constant with no check at all except a human
		// noticing, which is exactly what failed twice.
		t.Fatalf("the ratified canon could not be read, so the served contract version has nothing to be checked against: %v", err)
	}
	// `info.version` and not any other `version:` in the document: the file carries several.
	m := regexp.MustCompile(`(?m)^info:\n(?:[ \t]+.*\n)*?[ \t]+version: (\S+)`).FindSubmatch(src)
	if m == nil {
		t.Fatal("the canon carries no info.version: this gate reads the wrong document or the wrong shape")
	}
	if got, want := httpapi.ContractVersion, string(m[1]); got != want {
		t.Errorf("this build announces contract %s and the ratified canon is %s; the constant is raised in the same change as the code that implements a minor, never afterwards", got, want)
	}
}

// The `blocked` vocabulary this deployment serves must be the one the canon enumerates.
//
// ⛔ IT IS THE SECOND CHECK IN THIS ZONE WITH AN INDEPENDENT SOURCE, and it exists because the first
// one — the version number above — cannot see a SHAPE. Every other test of these values compares the
// wire to the same Go constant it was rendered from, which is self-consistent and passes at any
// value: rename both of them and the whole module stays green (measured by the pack's own adversarial
// pass, 11.09). That is the class PD-1 names, and `Blocked.code` is the one place it costs a
// contract: the canon declares a CLOSED enum there, so a value this build serves and the canon does
// not is a client generated against the canon meeting a word its stubs do not carry.
//
// It reads the canon rather than a copy of it, like its neighbour, and it asserts BOTH directions:
// a value served and not ratified is a wire ahead of the contract, a value ratified and not served
// is a contract ahead of the wire — and which of the two is a defect depends on the day, so the gate
// names what it saw instead of guessing.
func TestTheBlockedVocabularyServedIsTheOneTheCanonEnumerates(t *testing.T) {
	src, err := os.ReadFile(filepath.Join(canonPath))
	if err != nil {
		t.Fatalf("the ratified canon could not be read, so the served `blocked` vocabulary has nothing to be checked against: %v", err)
	}
	ratified, err := enumOfSchema(string(src), "Blocked")
	if err != nil {
		t.Fatalf("the canon's Blocked schema: %v — this gate reads the wrong document or the wrong shape", err)
	}
	// What this build can put in that member, written out rather than derived: a list a test walks is
	// a list somebody has to extend deliberately, which is the whole point of a closed vocabulary.
	served := map[string]bool{
		httpapi.CauseCreditHeld:  true,
		httpapi.CauseRunInFlight: true,
	}
	for v := range served {
		if !ratified[v] {
			t.Errorf("this build serves `blocked.code: %s` and the canon's enum does not carry it: %v", v, keys(ratified))
		}
	}
	for v := range ratified {
		if !served[v] {
			t.Errorf("the canon ratifies `blocked.code: %s` and this build never serves it: the wire is behind the contract", v)
		}
	}
}

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

// enumOfSchema returns the values of the one `enum:` inside the named schema of the canon.
//
// ⛔ THE SEARCH IS BOUNDED BY THE SCHEMA'S OWN BODY, and the bound is the whole of this function. The
// first edition was one regexp — `\n    Blocked:\n.*?\n +enum: \[…\]` — whose `.*?` was stopped by
// nothing: with the enum deleted from the canon it walked on and read the NEXT schema's, so a missing
// closed vocabulary came back as `[exhausted low ok]` from `Usage.state` seventy lines below. Red, and
// red for the wrong reason; move those two words under the following schema instead and the gate goes
// GREEN over a canon that no longer ratifies them at all. A gate that can read a neighbour's answer is
// not a second source, it is a coin.
//
// The body is every line indented deeper than the schema's own name, which is what YAML means by
// nesting and what the canon does everywhere. Pinned by TestTheSchemaEnumReaderStopsAtTheSchemasOwnBody,
// whose fixtures are exactly the two shapes above.
func enumOfSchema(canon, schema string) (map[string]bool, error) {
	head := "\n    " + schema + ":\n"
	i := strings.Index(canon, head)
	if i < 0 {
		return nil, fmt.Errorf("no schema %q in the document", schema)
	}
	body := canon[i+len(head):]
	// …up to the next line that is indented no deeper than the schema's name: the next schema, or the
	// end of the section.
	if end := regexp.MustCompile(`(?m)^ {0,4}\S`).FindStringIndex(body); end != nil {
		body = body[:end[0]]
	}
	m := regexp.MustCompile(`(?m)^ +enum: \[([^\]]*)\]`).FindStringSubmatch(body)
	if m == nil {
		return nil, fmt.Errorf("schema %q carries no enum", schema)
	}
	out := map[string]bool{}
	for _, v := range strings.Split(m[1], ",") {
		if v = strings.TrimSpace(v); v != "" {
			out[v] = true
		}
	}
	return out, nil
}

// The reader stops at the schema's own body — asserted on documents built for the question, because
// the live canon cannot show the failure this exists to prevent.
//
// Both fixtures are the adversarial pass's own posting: delete the enum and see whether a neighbour's
// is read instead. The first says the reader must REFUSE; the second says it must refuse even when the
// missing words are sitting a few lines below under another name, which is the shape that came back
// GREEN from the first edition.
func TestTheSchemaEnumReaderStopsAtTheSchemasOwnBody(t *testing.T) {
	const withIt = `
    Blocked:
      type: object
      properties:
        code:
          type: string
          enum: [credit_held, run_in_flight]
    Usage:
      properties:
        state:
          enum: [exhausted, low, ok]
`
	got, err := enumOfSchema(withIt, "Blocked")
	if err != nil || !got["credit_held"] || !got["run_in_flight"] || len(got) != 2 {
		t.Fatalf("the reader did not read the schema's own enum: %v (%v)", keys(got), err)
	}
	// The enum is GONE from Blocked and a neighbour still has one.
	const withoutIt = `
    Blocked:
      type: object
      properties:
        code:
          type: string
    Usage:
      properties:
        state:
          enum: [exhausted, low, ok]
`
	if got, err := enumOfSchema(withoutIt, "Blocked"); err == nil {
		t.Errorf("a schema with no enum answered %v: the reader walked into the next schema", keys(got))
	}
	// And the same, with the missing words present further down under another name — the shape that
	// makes a lenient reader answer RIGHT for the wrong document.
	const movedAway = `
    Blocked:
      type: object
      properties:
        code:
          type: string
    Somewhere:
      properties:
        code:
          enum: [credit_held, run_in_flight]
`
	if got, err := enumOfSchema(movedAway, "Blocked"); err == nil {
		t.Errorf("the words were read from the wrong schema: %v", keys(got))
	}
}

// ⛔ THE FAILURE-REASON VOCABULARY IS CLOSED IN THREE PLACES AND WAS COMPARED IN NONE.
//
// `RunFailureReason` is a closed enum in the canon, a switch in the store's validator and a CHECK
// constraint in the DDL. Nothing held the three together: measured 17.09, this package had zero hits
// for the name (and zero for its neighbours `PausedReason`, `BookStatus`, `ContractHaltReason` — the
// control that says the instrument was reading the right place). So a fourth value added to the code
// alone passed the whole battery GREEN on a host where the database tests are gated off, and met the
// constraint in production; one added to the canon alone left the wire behind the contract with
// nothing red.
//
// It reads the canon and the migrations rather than copies of them, like the two gates above. The
// SERVED list is written out here on purpose — the form its neighbour uses and for the same reason:
// a list a test walks is a list somebody has to extend deliberately, which is the whole point of a
// closed vocabulary. Adding a value now takes four deliberate edits, and that is the gate.
//
// ⚠ `attempts-exhausted` is checked to be OUTSIDE it, and that is not pedantry: the platform's own
// word for «we stopped restarting this run» lives in `run_attempts.exit_result`, a column the canon
// does not know and no constraint bounds, precisely so that the axis «who ended this run» can grow
// without touching the axis «is a retry worth offering». A word that leaked from one into the other
// would be a contract change nobody ratified.
func TestTheFailureReasonVocabularyIsTheSameInAllThreeOfItsCarriers(t *testing.T) {
	src, err := os.ReadFile(canonPath)
	if err != nil {
		t.Fatalf("the ratified canon could not be read, so the failure-reason vocabulary has nothing to be checked against: %v", err)
	}
	ratified, err := enumOfSchema(string(src), "RunFailureReason")
	if err != nil {
		t.Fatalf("the canon's RunFailureReason schema: %v — this gate reads the wrong document or the wrong shape", err)
	}
	served := map[string]bool{"source_unreadable": true, "service_error": true, "interrupted": true}
	for v := range served {
		if !ratified[v] {
			t.Errorf("this build serves failure_reason %q and the canon's enum does not carry it: %v", v, keys(ratified))
		}
	}
	for v := range ratified {
		if !served[v] {
			t.Errorf("the canon ratifies failure_reason %q and this build never serves it: the wire is behind the contract", v)
		}
	}
	// The VALIDATOR is asked, not read: a third list here would be the drift this gate exists to stop.
	for v := range ratified {
		if !pgstore.ValidFailureReason(v) {
			t.Errorf("the canon ratifies failure_reason %q and the store's validator refuses it: a run that "+
				"ended that way could not be written down at all", v)
		}
	}
	if pgstore.ValidFailureReason(runner.AttemptsExhaustedResult) {
		t.Errorf("%q is accepted as a contract failure reason: the platform's own word for an ending it "+
			"chose has leaked into the client's retry vocabulary", runner.AttemptsExhaustedResult)
	}
	// The DDL, from the LAST migration that constrains the column — migrations are append-only, so a
	// later one is the one in force. Reading a file by name would go stale the day it is narrowed.
	//
	// ⚠ THAT PREMISE HAS A CONDITION, and it is written ONCE, at `failureReasonsInDDL` below rather
	// than restated here: a migration whose `Up` narrows this vocabulary while its `Down` restores the
	// older list would be read WHOLE, and the rule this gate compares the canon against would be the
	// cancelled one. Said by pointer on purpose — a second copy of a condition is a second thing to go
	// stale, which is how this very comment came to state a conclusion its own mechanism had qualified.
	inDDL, from, err := failureReasonsInDDL()
	if err != nil {
		t.Fatal(err)
	}
	for v := range ratified {
		if !inDDL[v] {
			t.Errorf("the canon ratifies failure_reason %q and %s does not allow it: a run that ended that "+
				"way is refused by the database", v, from)
		}
	}
	for v := range inDDL {
		if !ratified[v] {
			t.Errorf("%s allows failure_reason %q and the canon does not ratify it: the schema is ahead of "+
				"the contract", from, v)
		}
	}
}

// failureReasonsInDDL returns the values the newest constraint on `runs.failure_reason` allows, and
// which migration it came from.
func failureReasonsInDDL() (map[string]bool, string, error) {
	dir := filepath.Join(zoneRoot, "internal", "pgstore", "migrations")
	files, err := os.ReadDir(dir)
	if err != nil {
		return nil, "", err
	}
	// Append-only, so the LAST file that mentions the constraint is the one in force. Names sort by
	// their number, which is what makes «last» well defined.
	//
	// ⛔ THE CONDITION UNDER WHICH THAT STOPS HOLDING, written down because the conclusion above is
	// load-bearing: this reads a migration WHOLE and does not tell `+goose Up` from `+goose Down`.
	// Today the two cannot disagree — exactly one migration constrains this column and its down path
	// drops the column rather than re-listing values — so «the last file» and «the rule in force» are
	// the same thing. The day a migration NARROWS the vocabulary in its Up while its Down restores
	// the older list, this function would read the Down's list as current and the gate would compare
	// the canon against a rule nothing enforces. The cure then is to cut each file at its `+goose
	// Down` marker, not to re-aim this at a file by name.
	re := regexp.MustCompile(`failure_reason in \(([^)]*)\)`)
	var newest string
	var match []string
	for _, f := range files {
		body, err := os.ReadFile(filepath.Join(dir, f.Name()))
		if err != nil {
			return nil, "", err
		}
		if m := re.FindStringSubmatch(string(body)); m != nil {
			newest, match = f.Name(), m
		}
	}
	if match == nil {
		// Not «no values»: a zero and a missing constraint are indistinguishable in a result, and one
		// of them means this gate measured nothing.
		return nil, "", fmt.Errorf("no migration constrains runs.failure_reason: this gate is reading the "+
			"wrong directory (%s) or the constraint has been dropped", dir)
	}
	out := map[string]bool{}
	for _, v := range strings.Split(match[1], ",") {
		if v = strings.Trim(strings.TrimSpace(v), "'"); v != "" {
			out[v] = true
		}
	}
	return out, newest, nil
}