package mcpsrv

import (
	"context"
	"database/sql"
	"path/filepath"
	"testing"

	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"

	"sourcecraft.dev/bigbes/sr-ht-ecore/grants"

	"sourcecraft.dev/bigbes/sr-ht-spec/authn"
	"sourcecraft.dev/bigbes/sr-ht-spec/service"
)

// mustGrants parses a grant string or fails the test.
func mustGrants(t *testing.T, s string) grants.Grants {
	t.Helper()
	g, err := grants.Parse(s)
	require.NoError(t, err, "parse grants %q", s)
	return g
}

// instancePrincipal is agentPrincipal as a tokens.sr.ht working token resolves
// it: the same agent, with a grant set behind it.
func instancePrincipal(t *testing.T, grantString string) authn.Principal {
	t.Helper()
	p := agentPrincipal()
	p.Plane = authn.PlaneInstance
	p.Grants = mustGrants(t, grantString)
	return p
}

// localPrincipal is agentPrincipal as spec's own agent_token resolves it.
func localPrincipal() authn.Principal {
	p := agentPrincipal()
	p.Plane = authn.PlaneLocal
	return p
}

// Every tool that serves content asks for spec:read, and asks for it per tool
// rather than at the Gate — /mcp carries the write tools too, and a surface-wide
// read grant would refuse a propose-only token at `initialize`, before it named
// anything.
func TestReadToolsRequireTheReadGrant(t *testing.T) {
	refused := instancePrincipal(t, "spec:propose")

	t.Run("spec_read", func(t *testing.T) {
		ctx := authn.WithPrincipal(context.Background(), refused)
		_, err := readHandler(ctx, Backend{}, readInput{Space: "~bigbes/rfcs", Document: "SPEC-0007"})
		assert.ErrorIs(t, err, authn.ErrMissingGrant)
	})

	t.Run("spec_list", func(t *testing.T) {
		ctx := authn.WithPrincipal(context.Background(), refused)
		_, err := listHandler(ctx, Backend{}, listInput{})
		assert.ErrorIs(t, err, authn.ErrMissingGrant)
	})

	t.Run("spec_search", func(t *testing.T) {
		ctx := authn.WithPrincipal(context.Background(), refused)
		_, err := searchHandler(ctx, Backend{}, searchInput{Query: "storage"})
		assert.ErrorIs(t, err, authn.ErrMissingGrant)
	})

	t.Run("spec_comment", func(t *testing.T) {
		ctx := authn.WithPrincipal(context.Background(), refused)
		_, err := commentHandler(ctx, commentFixture(t), commentInput{Proposal: 7})
		assert.ErrorIs(t, err, authn.ErrMissingGrant)
	})
}

// And every credential that carries no grants passes untouched, which is what
// keeps the agents configured today working: the local agent token and the
// owner's cookie have nothing to check.
func TestReadToolsPassEveryUngrantedCredential(t *testing.T) {
	for name, p := range map[string]authn.Principal{
		"local agent token":            localPrincipal(),
		"owner cookie":                 {Kind: authn.KindOwner, Owner: "bigbes"},
		"instance token, spec:read":    instancePrincipal(t, "spec:read"),
		"instance token, universal":    instancePrincipal(t, "*"),
		"instance token, both actions": instancePrincipal(t, "spec:read spec:propose"),
	} {
		t.Run(name, func(t *testing.T) {
			ctx := authn.WithPrincipal(context.Background(), p)
			assert.NoError(t, requireRead(ctx))

			// Listing threads goes all the way through with a fake service.
			out, err := commentHandler(ctx, commentFixture(t), commentInput{Proposal: 7})
			require.NoError(t, err)
			assert.NotEmpty(t, out.Threads)
		})
	}
}

// realWriter builds an actual *service.Service over a database nothing answers
// on, so that spec_propose's grant check here is service.Propose's own and not a
// copy of it. Propose refuses a principal before it opens anything, which is
// what makes an unreachable pool enough.
func realWriter(t *testing.T) *service.Service {
	t.Helper()
	root := t.TempDir()
	pool, err := sql.Open("postgres",
		"postgres://nobody@127.0.0.1:1/nothing?sslmode=disable&connect_timeout=1")
	require.NoError(t, err)
	t.Cleanup(func() { pool.Close() })

	svc, err := service.New(service.Config{
		Repos:            filepath.Join(root, "repos"),
		Cache:            filepath.Join(root, "cache"),
		Origin:           "https://spec.srht.bigb.es",
		ConnectionString: "postgres://nobody@127.0.0.1:1/nothing",
		Instance: authn.Instance{
			OwnerName:  "bigbes",
			OwnerEmail: "bigbes@gmail.com",
			AgentEmail: "agent@spec.srht.bigb.es",
		},
	}, pool)
	require.NoError(t, err)
	return svc
}

// proposeCall is one well-formed spec_propose, so the only thing a test varies
// is the credential behind it.
func proposeCall() proposeInput {
	return proposeInput{
		Space:     "~bigbes/rfcs",
		IfMatch:   "1f0c1d1a1e2b3c4d5e6f708192a3b4c5d6e7f809",
		Title:     "Add a note",
		Message:   "write it",
		Documents: []proposeDoc{{Path: "notes/a.md", Content: "---\nid: N-1\n---\n"}},
	}
}

// spec_propose asks for spec:propose, through the same service.Propose the REST
// surface calls — the rule is spelled once, below both write surfaces, and MCP
// gets it by going through it rather than by repeating it here.
func TestProposeToolRequiresTheProposeGrant(t *testing.T) {
	svc := realWriter(t)

	for _, grantString := range []string{"spec:read", "bench:upload"} {
		t.Run(grantString, func(t *testing.T) {
			ctx := authn.WithPrincipal(context.Background(), instancePrincipal(t, grantString))
			_, err := proposeHandler(ctx, svc, proposeCall())
			require.Error(t, err)
			assert.ErrorIs(t, err, service.ErrForbidden,
				"the refusal is the one this surface already uses for an unauthorised call")
			assert.ErrorIs(t, err, authn.ErrMissingGrant)
		})
	}
}

// And every credential that may propose clears it — the local agent token above
// all, which carries no grants and must keep working exactly as it does today.
func TestProposeToolAcceptsTheGrantedCredentials(t *testing.T) {
	svc := realWriter(t)

	for name, p := range map[string]authn.Principal{
		"local agent token":            localPrincipal(),
		"instance token, spec:propose": instancePrincipal(t, "spec:propose"),
		"instance token, universal":    instancePrincipal(t, "*"),
	} {
		t.Run(name, func(t *testing.T) {
			ctx := authn.WithPrincipal(context.Background(), p)
			// The write cannot land — there is no space and no database — but it
			// must not be turned away at the ACL.
			_, err := proposeHandler(ctx, svc, proposeCall())
			require.Error(t, err, "the fixture has no space, so this cannot succeed")
			assert.NotErrorIs(t, err, service.ErrForbidden, "%s must clear the write ACL", name)
			assert.NotErrorIs(t, err, authn.ErrMissingGrant)
		})
	}
}

// A grant is not a substitute for provenance. An instance token with the widest
// grant there is still cannot write without saying who wrote it — the refusal
// changes from authorization to provenance, and does not go away.
func TestProposeToolStillDemandsProvenanceOnBothPlanes(t *testing.T) {
	svc := realWriter(t)

	for name, p := range map[string]authn.Principal{
		"local":    localPrincipal(),
		"instance": instancePrincipal(t, "*"),
	} {
		t.Run(name, func(t *testing.T) {
			noSession := p
			noSession.Session = ""
			ctx := authn.WithPrincipal(context.Background(), noSession)

			_, err := proposeHandler(ctx, svc, proposeCall())
			require.Error(t, err)
			assert.NotErrorIs(t, err, service.ErrForbidden,
				"a missing session is a provenance failure, not an authorization one")

			_, err = noSession.AgentWriteFor("1f0c1d1a1e2b3c4d5e6f708192a3b4c5d6e7f809")
			assert.ErrorIs(t, err, authn.ErrMissingProvenance)
		})
	}
}