package app

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"sync"
	"time"
	"unicode/utf8"

	"finance-duck/internal/analytics"
	"finance-duck/internal/banking"
	"finance-duck/internal/classification"
	"finance-duck/internal/domain"
	"finance-duck/internal/journal"
	"finance-duck/internal/quotes"
)

// Settings holds preferences only, never credentials. ClassifyOnImport controls
// whether newly imported transactions are sent to the model at all; merchant
// rules always apply. PrivateNames is a semicolon-separated household redaction
// list when persisted in config.toml.
type Settings struct {
	Model            string   `json:"model"`
	ClassifyOnImport bool     `json:"classify_on_import"`
	PrivateNames     []string `json:"private_names"`
}
type Status struct {
	SyncError  string `json:"sync_error"`
	IndexError string `json:"index_error"`
	LastSync   string `json:"last_sync"`
	// SyncRetryAt is set only when every sync failure is a bank rate limit that
	// clears on its own; it is the earliest time an automatic retry is allowed.
	SyncRetryAt       string `json:"sync_retry_at,omitempty"`
	BankingConfigured bool   `json:"banking_configured"`
	AIConfigured      bool   `json:"ai_configured"`
}
type State struct {
	Data         domain.Dataset    `json:"data"`
	Revision     string            `json:"revision"`
	Status       Status            `json:"status"`
	Settings     Settings          `json:"settings"`
	Sessions     []banking.Session `json:"sessions"`
	CallbackURL  string            `json:"callback_url"`
	BankingAppID string            `json:"banking_app_id"`
	Connections  []Connection      `json:"connections"`
}
type operational struct {
	Sessions     []banking.Session  `json:"sessions"`
	LastSync     string             `json:"last_sync"`
	SyncError    string             `json:"sync_error"`
	SyncRetryAt  string             `json:"sync_retry_at,omitempty"`
	Consents     map[string]Consent `json:"consents"`
	AccountSync  map[string]string  `json:"account_sync"`
	BankingScope string             `json:"banking_scope"`
}
type App struct {
	mu               sync.Mutex
	dir              string
	journal          *journal.Store
	index            *analytics.Store
	indexed          string
	indexError       string
	settings         Settings
	ops              operational
	bank             banking.Provider
	classifier       classification.Client
	previews         map[string]Preview
	previewRun       *previewJob
	taxonomies       map[string]TaxonomyPreview
	csvImports       map[string]CSVImport
	authStates       map[string]authorization
	callbackURL      string
	bankingSettings  bankingSettings
	verifiedModels   []classification.VerifiedModel
	verifiedModelsAt time.Time
	// quotes needs no configuration: it reads a public endpoint, so its zero
	// value is the working client and tests replace it with a stub.
	quotes        quotes.Client
	syncRequested chan struct{}
}

// Settings this application has retired. They are read and discarded: a
// config.toml written by an older binary must never stop the new one from
// starting, and the next SaveSettings rewrites the file without them. An
// unrecognised key is still refused, so a typo cannot silently lose a
// preference.
var retiredSettings = map[string]bool{"include_amount": true}

func Open(dir string) (*App, error) {
	j, err := journal.Open(dir)
	if err != nil {
		return nil, err
	}
	a := &App{dir: dir, journal: j, previews: make(map[string]Preview), taxonomies: make(map[string]TaxonomyPreview), csvImports: make(map[string]CSVImport), authStates: make(map[string]authorization), syncRequested: make(chan struct{}, 1)}
	// Configurations written before this preference existed keep classifying
	// imports; only an explicit key switches it off.
	a.settings.ClassifyOnImport = true
	fail := func(e error) (*App, error) { j.Close(); return nil, e }
	if err = os.MkdirAll(filepath.Join(dir, "state"), 0700); err != nil {
		return fail(err)
	}
	if err = os.MkdirAll(filepath.Join(dir, "cache"), 0700); err != nil {
		return fail(err)
	}
	if b, e := os.ReadFile(filepath.Join(dir, "config.toml")); e == nil {
		for n, line := range strings.Split(string(b), "\n") {
			line = strings.TrimSpace(line)
			if line == "" || strings.HasPrefix(line, "#") {
				continue
			}
			k, v, ok := strings.Cut(line, "=")
			if !ok {
				return fail(fmt.Errorf("config.toml:%d: expected key = value", n+1))
			}
			k = strings.TrimSpace(k)
			v = strings.TrimSpace(v)
			switch k {
			case "classification_model":
				a.settings.Model, err = strconv.Unquote(v)
			case "private_names":
				a.settings.PrivateNames, err = parseNames(v)
			case "classify_on_import":
				a.settings.ClassifyOnImport, err = strconv.ParseBool(v)
			default:
				if !retiredSettings[k] {
					err = fmt.Errorf("unknown setting %q", k)
				}
			}
			if err != nil {
				return fail(fmt.Errorf("config.toml:%d: %w", n+1, err))
			}
		}
	} else if !os.IsNotExist(e) {
		return fail(e)
	}
	if b, e := os.ReadFile(filepath.Join(dir, "state", "sync-state.json")); e == nil {
		if err = json.Unmarshal(b, &a.ops); err != nil {
			return fail(fmt.Errorf("sync state: %w", err))
		}
	} else if !os.IsNotExist(e) {
		return fail(e)
	}
	if a.ops.Consents == nil {
		a.ops.Consents = make(map[string]Consent)
	}
	if a.ops.AccountSync == nil {
		a.ops.AccountSync = make(map[string]string)
	}
	apiKey, err := loadOpenRouterKey(filepath.Join(dir, "state", "openrouter.json"))
	if err != nil {
		return fail(err)
	}
	a.classifier = classification.Client{APIKey: apiKey, Model: a.settings.Model, PrivateNames: append([]string{}, a.settings.PrivateNames...)}
	if err = a.loadBankingSettings(); err != nil {
		return fail(err)
	}
	a.index, err = analytics.Open(filepath.Join(dir, "cache", "finance.duckdb"))
	if err != nil {
		return fail(err)
	}
	if _, err = a.snapshot(context.Background()); err != nil {
		a.index.Close()
		return fail(err)
	}
	return a, nil
}
func (a *App) Close() error {
	a.mu.Lock()
	defer a.mu.Unlock()
	return errors.Join(a.index.Close(), a.journal.Close())
}
func (a *App) snapshot(ctx context.Context) (State, error) {
	d, rev, err := a.journal.Load()
	if err != nil {
		return State{}, err
	}
	if rev != a.indexed {
		if err = a.index.Rebuild(ctx, d); err != nil {
			a.indexError = err.Error()
		} else {
			a.indexed = rev
			a.indexError = ""
		}
	}
	status := Status{SyncError: a.ops.SyncError, SyncRetryAt: a.ops.SyncRetryAt, LastSync: a.ops.LastSync, IndexError: a.indexError, BankingConfigured: a.bank != nil, AIConfigured: a.classifier.APIKey != ""}
	return State{Data: d, Revision: rev, Settings: a.settings, Sessions: copySessions(a.ops.Sessions), CallbackURL: a.callbackURL, BankingAppID: a.bankingSettings.AppID, Connections: a.connections(d), Status: status}, nil
}
func (a *App) Snapshot(ctx context.Context) (State, error) {
	a.mu.Lock()
	defer a.mu.Unlock()
	return a.snapshot(ctx)
}
func (a *App) commit(ctx context.Context, rev string, d domain.Dataset) (State, error) {
	if rev == "" {
		return State{}, errors.New("revision is required")
	}
	if _, err := a.journal.Commit(rev, d); err != nil {
		return State{}, err
	}
	return a.snapshot(ctx)
}
func (a *App) Mutate(ctx context.Context, rev string, fn func(*domain.Dataset) error) (State, error) {
	a.mu.Lock()
	defer a.mu.Unlock()
	s, err := a.snapshot(ctx)
	if err != nil {
		return State{}, err
	}
	if rev != s.Revision {
		return State{}, errors.New("revision conflict: reload before editing")
	}
	if err = fn(&s.Data); err != nil {
		return State{}, err
	}
	return a.commit(ctx, rev, s.Data)
}
func (a *App) Dashboard(ctx context.Context, f analytics.Filter) (analytics.Dashboard, error) {
	a.mu.Lock()
	defer a.mu.Unlock()
	if _, err := a.snapshot(ctx); err != nil {
		return analytics.Dashboard{}, err
	}
	if a.indexError != "" {
		return analytics.Dashboard{}, errors.New(a.indexError)
	}
	return a.index.Query(ctx, f)
}
func (a *App) Rebuild(ctx context.Context) (State, error) {
	a.mu.Lock()
	defer a.mu.Unlock()
	a.indexed = ""
	return a.snapshot(ctx)
}
func atomicFile(path string, b []byte) error {
	f, err := os.CreateTemp(filepath.Dir(path), ".state-*")
	if err != nil {
		return err
	}
	name := f.Name()
	defer os.Remove(name)
	if err = f.Chmod(0600); err == nil {
		_, err = f.Write(b)
	}
	if err == nil {
		err = f.Sync()
	}
	err = errors.Join(err, f.Close())
	if err != nil {
		return err
	}
	if err = os.Rename(name, path); err != nil {
		return err
	}
	dir, err := os.Open(filepath.Dir(path))
	if err != nil {
		return err
	}
	defer dir.Close()
	return dir.Sync()
}
func (a *App) saveOps() error {
	b, err := json.MarshalIndent(a.ops, "", "  ")
	if err != nil {
		return err
	}
	return atomicFile(filepath.Join(a.dir, "state", "sync-state.json"), append(b, '\n'))
}

func normalizeOpenRouterKey(key string) (string, error) {
	key = strings.TrimSpace(key)
	const invalid = "OpenRouter API key must be at most 4096 bytes and contain only non-whitespace ASCII characters"
	if len(key) > 4096 {
		return "", errors.New(invalid)
	}
	for i := range len(key) {
		if key[i] < 0x21 || key[i] > 0x7e {
			return "", errors.New(invalid)
		}
	}
	return key, nil
}

func normalizePrivateNames(values []string) ([]string, error) {
	out := make([]string, 0, len(values))
	for _, raw := range values {
		if !utf8.ValidString(raw) {
			return nil, errors.New("private names must be valid UTF-8")
		}
		name := strings.Join(strings.Fields(raw), " ")
		if name == "" {
			continue
		}
		if utf8.RuneCountInString(name) > 200 || strings.ContainsRune(name, ';') {
			return nil, errors.New("private names must be at most 200 characters and cannot contain semicolons")
		}
		out = append(out, name)
	}
	return out, nil
}

func parseNames(v string) ([]string, error) {
	raw, err := strconv.Unquote(v)
	if err != nil {
		return nil, err
	}
	return normalizePrivateNames(strings.Split(raw, ";"))
}

func loadOpenRouterKey(path string) (string, error) {
	f, err := os.Open(path)
	if os.IsNotExist(err) {
		return normalizeOpenRouterKey(os.Getenv("OPENROUTER_API_KEY"))
	}
	if err != nil {
		return "", errors.New("cannot read saved OpenRouter credential")
	}
	defer f.Close()
	// Bound encoded storage too, allowing JSON escapes for a maximum-size key.
	b, err := io.ReadAll(io.LimitReader(f, 32*1024+1))
	if err != nil {
		return "", errors.New("cannot read saved OpenRouter credential")
	}
	invalid := errors.New("invalid saved OpenRouter credential")
	if len(b) > 32*1024 {
		return "", invalid
	}
	// Require exactly one case-sensitive string field, rejecting duplicates,
	// unknown fields, null, and trailing JSON rather than silently disabling AI.
	dec := json.NewDecoder(bytes.NewReader(b))
	if token, err := dec.Token(); err != nil || token != json.Delim('{') {
		return "", invalid
	}
	if token, err := dec.Token(); err != nil || token != "api_key" {
		return "", invalid
	}
	token, err := dec.Token()
	key, ok := token.(string)
	if err != nil || !ok {
		return "", invalid
	}
	if token, err := dec.Token(); err != nil || token != json.Delim('}') {
		return "", invalid
	}
	if _, err := dec.Token(); err != io.EOF {
		return "", invalid
	}
	key, err = normalizeOpenRouterKey(key)
	if err != nil {
		return "", invalid
	}
	return key, nil
}

func (a *App) SaveOpenRouterKey(ctx context.Context, key string) (State, error) {
	a.mu.Lock()
	defer a.mu.Unlock()
	key, err := normalizeOpenRouterKey(key)
	if err != nil {
		return State{}, err
	}
	b, err := json.Marshal(struct {
		APIKey string `json:"api_key"`
	}{APIKey: key})
	if err != nil {
		return State{}, errors.New("cannot encode OpenRouter credential")
	}
	if err := atomicFile(filepath.Join(a.dir, "state", "openrouter.json"), append(b, '\n')); err != nil {
		return State{}, errors.New("cannot save OpenRouter credential")
	}
	a.classifier.APIKey = key
	return a.snapshot(ctx)
}

func (a *App) SaveSettings(ctx context.Context, s Settings) (State, error) {
	a.mu.Lock()
	defer a.mu.Unlock()
	s.Model = strings.TrimSpace(s.Model)
	if len(s.Model) > 200 {
		return State{}, errors.New("model name is too long")
	}
	names, err := normalizePrivateNames(s.PrivateNames)
	if err != nil {
		return State{}, err
	}
	s.PrivateNames = names
	b := []byte("# Preferences only. Manage secrets in Settings or environment variables, never this file.\n" +
		"classification_model = " + strconv.Quote(s.Model) + "\n" +
		"private_names = " + strconv.Quote(strings.Join(s.PrivateNames, "; ")) + "\n" +
		"classify_on_import = " + strconv.FormatBool(s.ClassifyOnImport) + "\n")
	if err := atomicFile(filepath.Join(a.dir, "config.toml"), b); err != nil {
		return State{}, err
	}
	a.settings = s
	a.classifier.Model = s.Model
	a.classifier.PrivateNames = append([]string{}, s.PrivateNames...)
	return a.snapshot(ctx)
}