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package acp

import (
	"bufio"
	"context"
	"encoding/json"
	"errors"
	"io"
	"strings"
	"testing"
	"time"

	"mm/internal/config"
	history "mm/internal/session"

	sdk "github.com/coder/acp-go-sdk"
	"github.com/firebase/genkit/go/ai"
)

// A prompt mixes text and attached files (resource_link): the text is kept
// as-is and the attachment becomes a path the model can read with its tools —
// bob has no embeddedContext capability, so the content itself never travels.
func TestFlattenTextAndResourceLink(t *testing.T) {
	got := flatten([]sdk.ContentBlock{
		sdk.TextBlock("fix the greeting"),
		sdk.ResourceLinkBlock("main.go", "file:///work/project/hello/main.go"),
	})
	want := "fix the greeting\n[attached file: /work/project/hello/main.go]"
	if got != want {
		t.Errorf("flatten:\n got %q\nwant %q", got, want)
	}
}

// Unknown kinds must render, not fail: the kind only drives the client's
// display, so "execute" is the safe default.
func TestToolKindDefaultsToExecute(t *testing.T) {
	cases := map[string]sdk.ToolKind{
		"read":    sdk.ToolKindRead,
		"edit":    sdk.ToolKindEdit,
		"execute": sdk.ToolKindExecute,
		"":        sdk.ToolKindExecute,
		"exotic":  sdk.ToolKindExecute,
	}
	for in, want := range cases {
		if got := toolKind(in); got != want {
			t.Errorf("toolKind(%q) = %q, want %q", in, got, want)
		}
	}
}

// The list the editor is shown must be exactly what session/prompt
// intercepts — no more (a /quit or /abort promised here would reach the model
// as a question; the editor's own stop key cancels a turn) and no less (a
// command that works but is not listed is one the user never finds). Names
// are bare: ACP clients add the slash.
func TestAvailableCommandsMatchWhatPromptIntercepts(t *testing.T) {
	want := []string{history.NewCommandName, "compact"}
	cmds := availableCommands()
	if len(cmds) != len(want) {
		t.Fatalf("availableCommands: %d command(s), want %d: %+v", len(cmds), len(want), cmds)
	}
	for i, c := range cmds {
		if c.Name != want[i] {
			t.Errorf("command %d is %q, want %q", i, c.Name, want[i])
		}
		if c.Description == "" {
			t.Errorf("%q has no description: the editor would show a bare name", c.Name)
		}
		if c.Input != nil {
			t.Errorf("%q takes no input, but an input spec is advertised", c.Name)
		}
		// Each advertised name must be recognised when it comes back as "/name".
		typed := "/" + c.Name
		if !history.IsNewCommand(typed) && !isCommand(typed, compactCommand) {
			t.Errorf("%q is advertised but session/prompt would hand it to the model", typed)
		}
	}
}

// Same rule as /new: the command is the whole line, spaces aside.
func TestIsCommandTrimsAndRequiresExactMatch(t *testing.T) {
	cases := map[string]bool{
		"/compact":        true,
		"  /compact\n":    true,
		"/compact now":    false,
		"/compacts":       false,
		"please /compact": false,
	}
	for in, want := range cases {
		if got := isCommand(in, compactCommand); got != want {
			t.Errorf("isCommand(%q) = %v, want %v", in, got, want)
		}
	}
}

// resetSession is what /new does to a session: the history goes back to the
// system prompt alone, the count says how much was dropped, and everything
// that is NOT the history — cwd, the "allow always" grants — survives, because
// the editor still sees the same session.
func TestResetSessionKeepsIdentityDropsHistory(t *testing.T) {
	s := &session{
		cwd:         "/work/project",
		messages:    history.Fresh("you are bob"),
		allowAlways: map[string]bool{"bash": true},
	}
	s.messages = append(s.messages, ai.NewUserTextMessage("ls"), ai.NewModelTextMessage("main.go"))

	if got := resetSession(s, "you are bob"); got != 2 {
		t.Errorf("forgotten = %d, want 2", got)
	}
	if len(s.messages) != 1 || s.messages[0].Role != ai.RoleSystem || s.messages[0].Text() != "you are bob" {
		t.Errorf("history after reset: %+v, want the system prompt alone", s.messages)
	}
	if s.cwd != "/work/project" {
		t.Errorf("cwd changed to %q", s.cwd)
	}
	if !s.allowAlways["bash"] {
		t.Error("the 'allow always' grant for bash was dropped")
	}

	// A second /new on a fresh session forgets nothing — and says so.
	if got := resetSession(s, "you are bob"); got != 0 {
		t.Errorf("forgotten on a fresh session = %d, want 0", got)
	}
}

// The command is recognised from a flattened prompt — the editor sends it as
// a text block, exactly as typed.
func TestNewCommandIsRecognisedFromPromptBlocks(t *testing.T) {
	if !history.IsNewCommand(flatten([]sdk.ContentBlock{sdk.TextBlock("/new")})) {
		t.Error("a text block '/new' is not recognised as the command")
	}
	if history.IsNewCommand(flatten([]sdk.ContentBlock{sdk.TextBlock("/new"), sdk.ResourceLinkBlock("main.go", "file:///w/main.go")})) {
		t.Error("'/new' with an attached file is a question about that file, not the command")
	}
}

// responseSessionID must recognise exactly the line the commands hook waits
// for: a response whose result carries a sessionId. A notification (no id)
// or a prompt response (no sessionId) must not fire the hook — the first
// would announce the commands before the editor knows the session, the
// second would never come from session/new at all.
func TestResponseSessionIDMatchesOnlySessionResponses(t *testing.T) {
	cases := map[string]struct {
		line string
		want sdk.SessionId
	}{
		"session/new response":   {`{"jsonrpc":"2.0","id":1,"result":{"sessionId":"bob-1-1"}}`, "bob-1-1"},
		"string id":              {`{"jsonrpc":"2.0","id":"a","result":{"sessionId":"bob-1-2"}}`, "bob-1-2"},
		"prompt response":        {`{"jsonrpc":"2.0","id":2,"result":{"stopReason":"end_turn"}}`, ""},
		"session/update":         {`{"jsonrpc":"2.0","method":"session/update","params":{"sessionId":"bob-1-1","update":{}}}`, ""},
		"request from the agent": {`{"jsonrpc":"2.0","id":3,"method":"session/request_permission","params":{"sessionId":"bob-1-1"}}`, ""},
		"garbage":                {`not json`, ""},
	}
	for name, c := range cases {
		got, ok := responseSessionID([]byte(c.line))
		if ok != (c.want != "") || got != c.want {
			t.Errorf("%s: responseSessionID = (%q, %v), want (%q, %v)", name, got, ok, c.want, c.want != "")
		}
	}
}

// The order on the wire is the whole point: the editor must read the
// session/new response — and so learn the session id — before the
// available_commands_update that names it. This drives the real SDK over
// pipes, playing the client by hand, and reads the raw lines back.
func TestAvailableCommandsAreSentAfterTheSessionNewResponse(t *testing.T) {
	clientToAgentR, clientToAgentW := io.Pipe()
	agentToClientR, agentToClientW := io.Pipe()
	t.Cleanup(func() {
		_ = clientToAgentW.Close()
		_ = agentToClientR.Close()
	})
	newFront(nil, "system prompt", nil, agentToClientW, clientToAgentR)

	go func() {
		_, _ = io.WriteString(clientToAgentW, `{"jsonrpc":"2.0","id":7,"method":"session/new","params":{"cwd":"/work","mcpServers":[]}}`+"\n")
	}()

	lines := make(chan string)
	go func() {
		sc := bufio.NewScanner(agentToClientR)
		for sc.Scan() {
			lines <- sc.Text()
		}
		close(lines)
	}()
	next := func() string {
		select {
		case l, ok := <-lines:
			if !ok {
				t.Fatal("agent closed its output before sending both lines")
			}
			return l
		case <-time.After(5 * time.Second):
			t.Fatal("timed out waiting for the agent's next line")
		}
		return ""
	}

	first, second := next(), next()

	sid, ok := responseSessionID([]byte(first))
	if !ok {
		t.Fatalf("first line is not the session/new response:\n%s", first)
	}
	var upd struct {
		Method string `json:"method"`
		Params struct {
			SessionId sdk.SessionId `json:"sessionId"`
			Update    struct {
				SessionUpdate     string                 `json:"sessionUpdate"`
				AvailableCommands []sdk.AvailableCommand `json:"availableCommands"`
			} `json:"update"`
		} `json:"params"`
	}
	if err := json.Unmarshal([]byte(second), &upd); err != nil {
		t.Fatalf("second line is not JSON: %v\n%s", err, second)
	}
	if upd.Method != "session/update" || upd.Params.Update.SessionUpdate != "available_commands_update" {
		t.Fatalf("second line is not an available_commands_update:\n%s", second)
	}
	if upd.Params.SessionId != sid {
		t.Errorf("commands announced for session %q, response created %q", upd.Params.SessionId, sid)
	}
	want := availableCommands()
	if len(upd.Params.Update.AvailableCommands) != len(want) {
		t.Fatalf("announced %d command(s), want %d: %+v", len(upd.Params.Update.AvailableCommands), len(want), upd.Params.Update.AvailableCommands)
	}
	for i, c := range upd.Params.Update.AvailableCommands {
		if c.Name != want[i].Name {
			t.Errorf("announced command %d is %q, want %q", i, c.Name, want[i].Name)
		}
	}
}

// --- /compact and /abort --------------------------------------------------------

// oneTurn is a question answered after one bash command: the smallest unit
// compaction cuts on.
func oneTurn(q string) []*ai.Message {
	return []*ai.Message{
		ai.NewUserTextMessage(q),
		ai.NewModelMessage(ai.NewToolRequestPart(&ai.ToolRequest{Ref: q, Name: "bash", Input: map[string]any{"command": "echo " + q}})),
		ai.NewMessage(ai.RoleTool, nil, ai.NewToolResponsePart(&ai.ToolResponse{Ref: q, Name: "bash", Output: q})),
		ai.NewModelMessage(ai.NewTextPart("done " + q)),
	}
}

func sessionWithTurns(qs ...string) *session {
	s := &session{cwd: "/work", messages: history.Fresh("You are Bob."), allowAlways: map[string]bool{"bash": true}}
	for _, q := range qs {
		s.messages = append(s.messages, oneTurn(q)...)
	}
	return s
}

// The three outcomes of /compact, in the REPL's words. Only the first one
// touches the history; the two others leave it — and the server's token
// count, which the caller resets on `compressed` alone — exactly as they were.
func TestCompactHistoryOutcomes(t *testing.T) {
	cfg := config.ContextConfig{Enabled: true, KeepLastTurns: 1, Threshold: 75, SummaryMaxTokens: 100}
	summary := func(context.Context, []*ai.Message) (string, error) { return "the user ran a and b", nil }
	explain := func(err error) string { return "explained: " + err.Error() }

	t.Run("compresses the turns older than the kept ones", func(t *testing.T) {
		s := sessionWithTurns("a", "b", "c")
		before := len(s.messages)
		line, compressed := compactHistory(context.Background(), s, cfg, summary, explain)
		if !compressed {
			t.Fatalf("compressed = false, line %q", line)
		}
		if !strings.HasPrefix(line, "🗜️ compressed 8 messages → 1 summary + 4 kept") {
			t.Errorf("report %q does not open with the REPL's words and the right counts", line)
		}
		if len(s.messages) >= before {
			t.Errorf("history has %d messages after compaction, %d before", len(s.messages), before)
		}
		if s.messages[0].Role != ai.RoleSystem || s.allowAlways["bash"] != true || s.cwd != "/work" {
			t.Error("compaction touched something other than the turns")
		}
	})

	t.Run("nothing to compact is said, not swallowed", func(t *testing.T) {
		s := sessionWithTurns("a")
		before := len(s.messages)
		line, compressed := compactHistory(context.Background(), s, cfg, summary, explain)
		if compressed || len(s.messages) != before {
			t.Errorf("compressed = %v, %d messages (was %d): a single kept turn must not move", compressed, len(s.messages), before)
		}
		if line != "🗜️ nothing to compact: 5 message(s), no turn older than the last 1" {
			t.Errorf("line %q", line)
		}
	})

	t.Run("a failed summary keeps the history and names the cause", func(t *testing.T) {
		s := sessionWithTurns("a", "b", "c")
		before := len(s.messages)
		failing := func(context.Context, []*ai.Message) (string, error) { return "", errors.New("server down") }
		line, compressed := compactHistory(context.Background(), s, cfg, failing, explain)
		if compressed || len(s.messages) != before {
			t.Errorf("compressed = %v, %d messages (was %d): a failure must leave the history alone", compressed, len(s.messages), before)
		}
		if line != "[compact: failed, history kept: explained: server down]" {
			t.Errorf("line %q", line)
		}
	})
}