package agent

import (
	"context"
	"encoding/json"
	"errors"
	"path/filepath"
	"reasonix/internal/state/sessionstore"
	"strings"
	"testing"

	"reasonix/internal/base/testenv"
	"reasonix/internal/contract/event"
	"reasonix/internal/contract/provider"
	"reasonix/internal/contract/tool"
)

func TestProjectionValidRejectsEditedPrefix(t *testing.T) {
	msgs := []provider.Message{
		{Role: provider.RoleSystem, Content: "sys"},
		{Role: provider.RoleUser, Content: "task-v1"},
		{Role: provider.RoleAssistant, Content: "done"},
		{Role: provider.RoleUser, Content: "next"},
	}
	st := sessionstore.CompactionState{
		TranscriptVersion: 2,
		PromptCacheKey:    "ws|sess|model",
		Projection: sessionstore.ContextProjection{
			Messages: []provider.Message{
				{Role: provider.RoleSystem, Content: "sys"},
				{Role: provider.RoleUser, Content: "summary"},
			},
			TranscriptVersion: 2,
			CoveredCount:      3,
			CoveredPrefixHash: sessionstore.CoveredPrefixHash(msgs, 3),
		},
	}
	if !projectionValid(st, msgs, "ws|sess|model", nil) {
		t.Fatal("expected valid projection for matching prefix")
	}
	// Append-only growth still valid.
	grown := append(append([]provider.Message(nil), msgs...), provider.Message{Role: provider.RoleAssistant, Content: "more"})
	if !projectionValid(st, grown, "ws|sess|model", nil) {
		t.Fatal("append-only growth should keep projection valid")
	}
	// Prefix edit invalidates.
	edited := append([]provider.Message(nil), msgs...)
	edited[1].Content = "task-EDITED"
	if projectionValid(st, edited, "ws|sess|model", nil) {
		t.Fatal("edited covered prefix must invalidate projection")
	}
}

func TestProjectionValidRejectsCacheKeyMismatch(t *testing.T) {
	msgs := []provider.Message{
		{Role: provider.RoleSystem, Content: "sys"},
		{Role: provider.RoleUser, Content: "task"},
	}
	hash := sessionstore.CoveredPrefixHash(msgs, 2)
	st := sessionstore.CompactionState{
		TranscriptVersion: 1,
		PromptCacheKey:    "ws|sess|model-a",
		Projection: sessionstore.ContextProjection{
			Messages:          []provider.Message{{Role: provider.RoleSystem, Content: "sys"}},
			CoveredCount:      2,
			CoveredPrefixHash: hash,
			TranscriptVersion: 1,
		},
	}
	if projectionValid(st, msgs, "ws|sess|model-b", nil) {
		t.Fatal("model/lineage key mismatch must invalidate projection")
	}
	if !projectionValid(st, msgs, "ws|sess|model-a", nil) {
		t.Fatal("matching key should be valid")
	}
	// Fail closed: blank stored key is rejected when current key is known.
	st.PromptCacheKey = ""
	if projectionValid(st, msgs, "ws|sess|model-a", nil) {
		t.Fatal("missing sidecar cache key must invalidate when lineage is known")
	}
	// Missing prefix hash is always rejected.
	st.PromptCacheKey = "ws|sess|model-a"
	st.Projection.CoveredPrefixHash = ""
	if projectionValid(st, msgs, "ws|sess|model-a", nil) {
		t.Fatal("missing CoveredPrefixHash must invalidate projection")
	}
}

func TestCoveredPrefixHashIncludesProviderVisibleFields(t *testing.T) {
	base := []provider.Message{{
		Role:               provider.RoleAssistant,
		Content:            "answer",
		ReasoningContent:   "think",
		ReasoningID:        "rid-1",
		ReasoningStatus:    "completed",
		ReasoningSignature: "sig-1",
		Images:             []string{"data:image/png;base64,AAA"},
		ToolCalls: []provider.ToolCall{{
			ID: "c1", Name: "f", Arguments: `{}`, ThoughtSignature: "ts-1",
		}},
		ResponsesItems: []json.RawMessage{json.RawMessage(`{"type":"web_search_call"}`)},
	}}
	h1 := sessionstore.CoveredPrefixHash(base, 1)
	if h1 == "" {
		t.Fatal("empty fingerprint")
	}
	// Each provider-visible field change must move the hash.
	cases := []struct {
		name string
		mut  func([]provider.Message)
	}{
		{"images", func(m []provider.Message) { m[0].Images = []string{"data:image/png;base64,BBB"} }},
		{"reasoning_id", func(m []provider.Message) { m[0].ReasoningID = "rid-2" }},
		{"reasoning_status", func(m []provider.Message) { m[0].ReasoningStatus = "in_progress" }},
		{"reasoning_signature", func(m []provider.Message) { m[0].ReasoningSignature = "sig-2" }},
		{"thought_signature", func(m []provider.Message) { m[0].ToolCalls[0].ThoughtSignature = "ts-2" }},
		{"responses_items", func(m []provider.Message) {
			m[0].ResponsesItems = []json.RawMessage{json.RawMessage(`{"type":"other"}`)}
		}},
	}
	for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
			mutated := []provider.Message{base[0]}
			mutated[0].ToolCalls = append([]provider.ToolCall(nil), base[0].ToolCalls...)
			mutated[0].Images = append([]string(nil), base[0].Images...)
			mutated[0].ResponsesItems = append([]json.RawMessage(nil), base[0].ResponsesItems...)
			tc.mut(mutated)
			if sessionstore.CoveredPrefixHash(mutated, 1) == h1 {
				t.Fatalf("%s change did not alter sessionstore.CoveredPrefixHash", tc.name)
			}
		})
	}
}

func TestLoadProjectionSidecarRebindsMatchingContentAcrossLineage(t *testing.T) {
	dir := testenv.TempDir(t)
	path := filepath.Join(dir, "s.jsonl")
	msgs := []provider.Message{
		{Role: provider.RoleSystem, Content: "sys"},
		{Role: provider.RoleUser, Content: "task"},
	}
	hash := sessionstore.CoveredPrefixHash(msgs, 2)
	if err := sessionstore.SaveCompactionState(path, sessionstore.CompactionState{
		SchemaVersion:     sessionstore.CompactionStateSchemaV1,
		PromptCacheKey:    "ws|s|other-model",
		TranscriptVersion: 1,
		Projection: sessionstore.ContextProjection{
			Messages:          []provider.Message{{Role: provider.RoleSystem, Content: "sys summary"}},
			CoveredCount:      2,
			CoveredPrefixHash: hash,
		},
	}); err != nil {
		t.Fatal(err)
	}
	sess := sessionstore.NewSession("sys")
	sess.Add(provider.Message{Role: provider.RoleUser, Content: "task"})
	a := New(nil, nil, sess, Options{
		SessionPath: path,
		WorkspaceID: "ws",
		ModelRef:    "this-model",
	}, event.Discard)
	// New() already called LoadProjectionSidecar; the projection body matches
	// the canonical covered prefix, so it must be rebound to the current key
	// instead of being dropped (upgrade / model-switch path).
	if len(a.sess.win.compactionState.Projection.Messages) == 0 {
		t.Fatal("matching projection body was dropped on lineage change")
	}
	wantKey := promptCacheKey("ws", sessionstore.BranchID(path), "this-model")
	if a.sess.win.compactionState.PromptCacheKey != wantKey {
		t.Fatalf("PromptCacheKey = %q, want %q", a.sess.win.compactionState.PromptCacheKey, wantKey)
	}
	if a.sess.win.checkpointState != "restored" {
		t.Fatalf("checkpointState = %q, want restored", a.sess.win.checkpointState)
	}
	// The rebind must be persisted so the next launch does not re-downgrade.
	disk, ok, err := sessionstore.LoadCompactionState(path)
	if err != nil || !ok {
		t.Fatalf("sidecar should remain on disk: ok=%v err=%v", ok, err)
	}
	if disk.PromptCacheKey != wantKey {
		t.Fatalf("persisted PromptCacheKey = %q, want %q", disk.PromptCacheKey, wantKey)
	}
}

func TestLoadProjectionSidecarDropsForeignCacheKey(t *testing.T) {
	dir := testenv.TempDir(t)
	path := filepath.Join(dir, "s.jsonl")
	msgs := []provider.Message{{Role: provider.RoleSystem, Content: "sys"}}
	// Content validation must fail despite a model-only key change: lineage
	// rebinding cannot resurrect a projection whose canonical prefix differs.
	foreign := []provider.Message{{Role: provider.RoleSystem, Content: "sys-old"}}
	if err := sessionstore.SaveCompactionState(path, sessionstore.CompactionState{
		SchemaVersion:  sessionstore.CompactionStateSchemaV1,
		PromptCacheKey: "ws|s|other-model",
		Projection: sessionstore.ContextProjection{
			Messages:          msgs,
			CoveredCount:      1,
			CoveredPrefixHash: sessionstore.CoveredPrefixHash(foreign, 1),
		},
	}); err != nil {
		t.Fatal(err)
	}
	a := New(nil, nil, sessionstore.NewSession("sys"), Options{
		SessionPath: path,
		WorkspaceID: "ws",
		ModelRef:    "this-model",
	}, event.Discard)
	// New() already called LoadProjectionSidecar; mismatched content must drop
	// the projection body and keep the sidecar file for the other model.
	if len(a.sess.win.compactionState.Projection.Messages) != 0 {
		t.Fatalf("foreign projection loaded: %+v", a.sess.win.compactionState.Projection)
	}
	if _, ok, err := sessionstore.LoadCompactionState(path); err != nil || !ok {
		t.Fatalf("sidecar should remain on disk: ok=%v err=%v", ok, err)
	}
}

func TestForceThresholdNoopReturnsCompactionRequired(t *testing.T) {
	// Huge tool result is entirely in the recent tail → no fold region, but
	// estimate exceeds force; preflight must refuse (not mid-turn).
	huge := strings.Repeat("word ", 5000)
	sess := &sessionstore.Session{Messages: []provider.Message{
		{Role: provider.RoleSystem, Content: "sys"},
		{Role: provider.RoleUser, Content: "task"},
		{Role: provider.RoleAssistant, ToolCalls: []provider.ToolCall{{ID: "1", Name: "read", Arguments: "{}"}}},
		{Role: provider.RoleTool, ToolCallID: "1", Name: "read", Content: huge},
	}}
	a := New(&fakeProvider{reply: "unused"}, tool.NewRegistry(), sess, Options{
		ContextWindow: 200,
		CompactRatio:  0.5,
	}, event.Discard)

	_, err := a.window().contextManager().Prepare(context.Background(), ContextPreparePolicy{Trigger: CompactionTriggerPressure})
	if err == nil {
		t.Fatal("expected ErrCompactionRequired when force threshold has no fold region")
	}
	if !errors.Is(err, ErrCompactionRequired) {
		t.Fatalf("err = %v, want ErrCompactionRequired", err)
	}
}

func TestCompactInstallsCoveredPrefixHash(t *testing.T) {
	fp := &fakeProvider{reply: "digest"}
	sess := sessionstore.NewSession("sys")
	for range 8 {
		sess.Add(provider.Message{Role: provider.RoleUser, Content: strings.Repeat("u", 80)})
		sess.Add(provider.Message{Role: provider.RoleAssistant, Content: strings.Repeat("a", 600)})
	}
	dir := testenv.TempDir(t)
	path := filepath.Join(dir, "s.jsonl")
	a := New(fp, tool.NewRegistry(), sess, Options{
		ContextWindow: 2000,
		ArchiveDir:    dir,
		SessionPath:   path,
		WorkspaceID:   "ws",
		ModelRef:      "m",
	}, event.Discard)
	if _, err := a.CompactNow(context.Background(), CompactRequest{}); err != nil {
		t.Fatal(err)
	}
	st := a.sess.win.compactionState
	if st.Projection.CoveredPrefixHash == "" {
		t.Fatal("CoveredPrefixHash not set")
	}
	if st.PromptCacheKey != promptCacheKey("ws", sessionstore.BranchID(path), "m") {
		t.Fatalf("PromptCacheKey = %q", st.PromptCacheKey)
	}
	msgs, _ := sess.SnapshotMessagesVersion()
	if !projectionValid(st, msgs, st.PromptCacheKey, nil) {
		t.Fatal("fresh projection should validate")
	}
}

func TestLoadProjectionSidecarSaysWhyAFoldWasNotReused(t *testing.T) {
	cases := []struct {
		name   string
		key    string
		covers []provider.Message
		want   ProjectionDrop
	}{
		{"history rewritten under the same lineage", "", []provider.Message{{Role: provider.RoleSystem, Content: "sys-old"}}, ProjectionDropHistory},
		{"history rewritten under another lineage", "ws|s|other-model", []provider.Message{{Role: provider.RoleSystem, Content: "sys-old"}}, ProjectionDropLineage},
		{"still valid", "", []provider.Message{{Role: provider.RoleSystem, Content: "sys"}}, ProjectionDropNone},
	}
	for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
			path := filepath.Join(testenv.TempDir(t), "s.jsonl")
			key := tc.key
			if key == "" {
				key = promptCacheKey("ws", sessionstore.BranchID(path), "this-model")
			}
			if err := sessionstore.SaveCompactionState(path, sessionstore.CompactionState{
				SchemaVersion:  sessionstore.CompactionStateSchemaV1,
				PromptCacheKey: key,
				Projection: sessionstore.ContextProjection{
					Messages:          []provider.Message{{Role: provider.RoleSystem, Content: "summary"}},
					CoveredCount:      1,
					CoveredPrefixHash: sessionstore.CoveredPrefixHash(tc.covers, 1),
				},
			}); err != nil {
				t.Fatal(err)
			}
			a := New(nil, nil, sessionstore.NewSession("sys"), Options{SessionPath: path, WorkspaceID: "ws", ModelRef: "this-model"}, event.Discard)
			if got := a.ProjectionDropped(); got != tc.want {
				t.Fatalf("ProjectionDropped = %q, want %q", got, tc.want)
			}
		})
	}
}

func TestProjectionDroppedIsClearedByANewBinding(t *testing.T) {
	path := filepath.Join(testenv.TempDir(t), "s.jsonl")
	if err := sessionstore.SaveCompactionState(path, sessionstore.CompactionState{
		SchemaVersion:  sessionstore.CompactionStateSchemaV1,
		PromptCacheKey: promptCacheKey("ws", sessionstore.BranchID(path), "m"),
		Projection: sessionstore.ContextProjection{
			Messages: []provider.Message{{Role: provider.RoleSystem, Content: "summary"}}, CoveredCount: 1,
			CoveredPrefixHash: sessionstore.CoveredPrefixHash([]provider.Message{{Role: provider.RoleSystem, Content: "other"}}, 1),
		},
	}); err != nil {
		t.Fatal(err)
	}
	a := New(nil, nil, sessionstore.NewSession("sys"), Options{SessionPath: path, WorkspaceID: "ws", ModelRef: "m"}, event.Discard)
	if a.ProjectionDropped() != ProjectionDropHistory {
		t.Fatalf("setup: ProjectionDropped = %q", a.ProjectionDropped())
	}
	a.BindSessionPath(filepath.Join(testenv.TempDir(t), "fresh.jsonl"), true)
	if got := a.ProjectionDropped(); got != ProjectionDropNone {
		t.Fatalf("a session with no sidecar still reports %q", got)
	}
}