// Copyright (c) 2026 Storm Dragon
// SPDX-License-Identifier: GPL-3.0-or-later

// Package codex presents completed messages supplied by the opt-in Codex bridge.
package codex

import (
	"fmt"
	"slices"
	"strings"

	"git.stormux.org/storm/fenrir/internal/applicationoverrides"
	"git.stormux.org/storm/fenrir/internal/command"
	"git.stormux.org/storm/fenrir/internal/config"
	"git.stormux.org/storm/fenrir/internal/i18n"
	"git.stormux.org/storm/fenrir/internal/presentation"
	"git.stormux.org/storm/fenrir/internal/screen"
)

// Event is a versioned, terminal-addressed packet, never a reader command.
// Message chunks are committed only after the entire completed message arrives.
type Event struct {
	Version  int    `json:"version"`
	Window   string `json:"window"`
	Terminal int    `json:"terminal"`
	Session  string `json:"session"`
	Epoch    int64  `json:"epoch"`
	Kind     string `json:"kind"`
	Status   string `json:"status,omitempty"`
	ID       string `json:"id,omitempty"`
	Text     string `json:"text,omitempty"`
	Part     int    `json:"part,omitempty"`
	Parts    int    `json:"parts,omitempty"`
	Baseline bool   `json:"baseline,omitempty"`
}

type storedMessage struct{ id, text string }

type Adapter struct {
	session, status string
	epoch           int64
	history         []storedMessage
	pending         []presentation.Message
	chunkID         string
	chunks          []string
	chunkBytes      int
	chunkParts      int
	closed          bool
}

func (*Adapter) Name() string { return "Codex" }
func (*Adapter) Configure(settings *config.Settings) {
	settings.Review.LeaveReviewOnCursorChange = true
}

// Suspension discards automatic announcements, retaining history and deduplication.
func (a *Adapter) Reset() { a.pending = nil }
func (a *Adapter) Close() { *a = Adapter{} }

func (a *Adapter) Accept(event Event) error {
	if event.Version != 1 || event.Session == "" || len(event.Session) > 128 || event.Epoch < 1 {
		return fmt.Errorf("invalid Codex event version or session")
	}
	if event.Epoch < a.epoch || a.session != "" && a.session != event.Session && (event.Kind != "status" || event.Epoch <= a.epoch) {
		return fmt.Errorf("another Codex session is attached")
	}
	if event.Kind == "status" {
		switch event.Status {
		case "idle", "working", "permission", "question", "done", "interrupted", "closed", "error":
		default:
			return fmt.Errorf("invalid Codex status")
		}
	} else if event.Kind != "message" || event.ID == "" || len(event.ID) > 256 || event.Parts < 1 || event.Parts > 4096 || event.Part < 0 || event.Part >= event.Parts || len(event.Text) > 6000 {
		return fmt.Errorf("invalid Codex message chunk")
	}
	if a.session != event.Session {
		*a = Adapter{session: event.Session, epoch: event.Epoch}
	}
	a.epoch = event.Epoch
	if event.Kind == "status" {
		a.status, a.closed = event.Status, event.Status == "closed"
		return nil
	}
	if slices.ContainsFunc(a.history, func(message storedMessage) bool { return message.id == event.ID }) {
		return nil
	}
	if event.Part == 0 {
		a.chunkID, a.chunks, a.chunkBytes = event.ID, nil, 0
		a.chunkParts = event.Parts
	}
	if a.chunkID != event.ID || len(a.chunks) != event.Part || a.chunkParts != event.Parts {
		return fmt.Errorf("Codex chunks must arrive in order")
	}
	a.chunkBytes += len(event.Text)
	if a.chunkBytes > 1024*1024 {
		a.chunkID, a.chunks, a.chunkBytes = "", nil, 0
		return fmt.Errorf("Codex message exceeds 1 MiB")
	}
	a.chunks = append(a.chunks, event.Text)
	if len(a.chunks) != event.Parts {
		return nil
	}
	text := strings.TrimSpace(strings.Join(a.chunks, ""))
	a.chunkID, a.chunks, a.chunkBytes = "", nil, 0
	if text == "" {
		return nil
	}
	a.history = append([]storedMessage{{event.ID, text}}, a.history...)
	if len(a.history) > 9 {
		a.history = a.history[:9]
	}
	if !event.Baseline {
		a.pending = append(a.pending, presentation.Message{Text: text})
	}
	return nil
}

func (a *Adapter) Observe(next screen.Snapshot) applicationoverrides.Frame {
	frame := applicationoverrides.Frame{Recognized: !a.closed, OwnsPresentation: !a.closed, InputCursor: true, Activity: !a.closed && a.status == "working"}
	// Only the composer can produce automatic typing/deletion echo. Tool output
	// and transcript rows must never be interpreted as text typed by the user.
	for row := next.Rows - 1; row >= max(0, next.Rows-12); row-- {
		line := string(next.Line(row))
		if col := strings.IndexRune(line, '›'); col >= 0 && strings.TrimSpace(line[:col]) == "" {
			left := len([]rune(line[:col])) + 2
			if next.Y >= row && next.Y < next.Rows && next.X >= left {
				frame.Input = &screen.Region{Left: left, Top: row, Right: next.Cols - 1, Bottom: next.Y}
			}
			break
		}
	}
	frame.Updates, a.pending = a.pending, nil
	return frame
}

func (a *Adapter) Command(id command.ID) (presentation.CommandResult, bool) {
	ids := []command.ID{command.ReadLiveRegion1, command.ReadLiveRegion2, command.ReadLiveRegion3, command.ReadLiveRegion4, command.ReadLiveRegion5, command.ReadLiveRegion6, command.ReadLiveRegion7, command.ReadLiveRegion8, command.ReadLiveRegion9}
	if slot := slices.Index(ids, id); slot >= 0 {
		text := i18n.T("No Codex message received")
		if slot < len(a.history) {
			text = a.history[slot].text
		}
		return presentation.CommandResult{Text: text}, true
	}
	if id == command.ListReadingRegions {
		return presentation.CommandResult{Text: i18n.T("Codex regions: 1 to 9 recent messages, newest first; 0 status")}, true
	}
	if id == command.ReadLiveRegion10 {
		text := i18n.T("Waiting for Codex bridge")
		switch a.status {
		case "idle":
			text = i18n.T("Codex ready")
		case "working":
			text = i18n.T("Codex working")
		case "permission":
			text = i18n.T("Codex waiting for approval")
		case "question":
			text = i18n.T("Codex waiting for an answer")
		case "done":
			text = i18n.T("Codex finished")
		case "interrupted":
			text = i18n.T("Codex interrupted")
		case "error":
			text = i18n.T("Codex bridge error")
		}
		return presentation.CommandResult{Text: text}, true
	}
	return presentation.CommandResult{}, false
}