// Package store persists proxy history to SQLite in WAL mode. Request
// and response bytes are stored as-received where possible (see the
// Exact fields) rather than re-serialized from a parsed representation.
// An FTS5 index (history_fts) mirrors method/host/path and the raw
// request/response text for full-text search - see Search.
package store

import (
	"database/sql"
	"fmt"
	"strings"
	"time"

	_ "modernc.org/sqlite"
)

const schema = `
CREATE TABLE IF NOT EXISTS history (
	id             INTEGER PRIMARY KEY AUTOINCREMENT,
	started_at     INTEGER NOT NULL,
	duration_ms    INTEGER NOT NULL,
	method         TEXT NOT NULL,
	scheme         TEXT NOT NULL,
	host           TEXT NOT NULL,
	path           TEXT NOT NULL,
	status_code    INTEGER,
	request_raw    BLOB NOT NULL,
	response_raw   BLOB,
	request_exact  INTEGER NOT NULL,
	response_exact INTEGER NOT NULL,
	error          TEXT NOT NULL DEFAULT '',
	source         TEXT NOT NULL DEFAULT 'proxy'
);

CREATE VIRTUAL TABLE IF NOT EXISTS history_fts USING fts5(
	method, host, path, request_text, response_text,
	tokenize = 'unicode61 remove_diacritics 2'
);
`

// Store is a handle to the history database. Safe for concurrent use.
type Store struct {
	db *sql.DB
}

// Open opens (creating if needed) the SQLite database at path in WAL mode.
func Open(path string) (*Store, error) {
	db, err := sql.Open("sqlite", path)
	if err != nil {
		return nil, fmt.Errorf("open db: %w", err)
	}
	// modernc.org/sqlite has no real connection pooling benefit here and
	// SQLite only supports one writer at a time; serializing access
	// through a single connection avoids SQLITE_BUSY entirely.
	db.SetMaxOpenConns(1)

	for _, pragma := range []string{
		"PRAGMA journal_mode = WAL",
		"PRAGMA synchronous = NORMAL",
		"PRAGMA foreign_keys = ON",
	} {
		if _, err := db.Exec(pragma); err != nil {
			db.Close()
			return nil, fmt.Errorf("%s: %w", pragma, err)
		}
	}
	if _, err := db.Exec(schema); err != nil {
		db.Close()
		return nil, fmt.Errorf("create schema: %w", err)
	}
	// Added after the initial schema; ignore the "duplicate column" error
	// on databases that already have it.
	db.Exec("ALTER TABLE history ADD COLUMN source TEXT NOT NULL DEFAULT 'proxy'")
	// Backfill history_fts for rows inserted before it existed. A no-op
	// once caught up, since every Insert keeps both tables in sync.
	if _, err := db.Exec(`
		INSERT INTO history_fts (rowid, method, host, path, request_text, response_text)
		SELECT id, method, host, path, CAST(request_raw AS TEXT), COALESCE(CAST(response_raw AS TEXT), '')
		FROM history WHERE id NOT IN (SELECT rowid FROM history_fts)
	`); err != nil {
		db.Close()
		return nil, fmt.Errorf("backfill search index: %w", err)
	}
	return &Store{db: db}, nil
}

// Close closes the underlying database.
func (s *Store) Close() error {
	return s.db.Close()
}

// Entry is one captured request/response pair.
type Entry struct {
	ID            int64
	StartedAt     time.Time
	Duration      time.Duration
	Method        string
	Scheme        string
	Host          string
	Path          string
	StatusCode    int // 0 if no response was received
	RequestRaw    []byte
	ResponseRaw   []byte // nil if no response was received
	RequestExact  bool   // true if RequestRaw is wire-exact, false if reconstructed (e.g. HTTP/2)
	ResponseExact bool
	Error         string // network/transport error, if the request never got a response
	Source        string // "proxy" or "repeater"
}

// Summary is the lightweight metadata used for the history list view -
// no request/response bodies.
type Summary struct {
	ID         int64
	StartedAt  time.Time
	Duration   time.Duration
	Method     string
	Scheme     string
	Host       string
	Path       string
	StatusCode int
	ReqSize    int
	RespSize   int
	Error      string
	Source     string
}

// Insert stores e (and indexes it for search) and returns its assigned ID.
func (s *Store) Insert(e *Entry) (int64, error) {
	var statusCode any
	if e.StatusCode != 0 {
		statusCode = e.StatusCode
	}
	source := e.Source
	if source == "" {
		source = "proxy"
	}

	tx, err := s.db.Begin()
	if err != nil {
		return 0, fmt.Errorf("begin insert: %w", err)
	}
	defer tx.Rollback()

	res, err := tx.Exec(
		`INSERT INTO history
			(started_at, duration_ms, method, scheme, host, path, status_code,
			 request_raw, response_raw, request_exact, response_exact, error, source)
		 VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
		e.StartedAt.UnixMilli(), e.Duration.Milliseconds(), e.Method, e.Scheme, e.Host, e.Path,
		statusCode, e.RequestRaw, e.ResponseRaw, boolToInt(e.RequestExact), boolToInt(e.ResponseExact), e.Error, source,
	)
	if err != nil {
		return 0, fmt.Errorf("insert history entry: %w", err)
	}
	id, err := res.LastInsertId()
	if err != nil {
		return 0, fmt.Errorf("insert history entry: %w", err)
	}

	if _, err := tx.Exec(
		`INSERT INTO history_fts (rowid, method, host, path, request_text, response_text)
		 VALUES (?, ?, ?, ?, ?, ?)`,
		id, e.Method, e.Host, e.Path, string(e.RequestRaw), string(e.ResponseRaw),
	); err != nil {
		return 0, fmt.Errorf("index history entry: %w", err)
	}

	if err := tx.Commit(); err != nil {
		return 0, fmt.Errorf("commit insert: %w", err)
	}
	return id, nil
}

// List returns up to limit history summaries older than beforeID (or the
// most recent if beforeID is 0), newest first.
func (s *Store) List(limit int, beforeID int64) ([]Summary, error) {
	if limit <= 0 || limit > 1000 {
		limit = 200
	}
	if beforeID <= 0 {
		beforeID = 1<<63 - 1
	}
	rows, err := s.db.Query(
		`SELECT id, started_at, duration_ms, method, scheme, host, path,
		        COALESCE(status_code, 0), length(request_raw), COALESCE(length(response_raw), 0), error, source
		 FROM history WHERE id < ? ORDER BY id DESC LIMIT ?`,
		beforeID, limit,
	)
	if err != nil {
		return nil, fmt.Errorf("list history: %w", err)
	}
	defer rows.Close()

	var out []Summary
	for rows.Next() {
		var sum Summary
		var startedAt, durationMs int64
		if err := rows.Scan(&sum.ID, &startedAt, &durationMs, &sum.Method, &sum.Scheme, &sum.Host, &sum.Path,
			&sum.StatusCode, &sum.ReqSize, &sum.RespSize, &sum.Error, &sum.Source); err != nil {
			return nil, fmt.Errorf("scan history row: %w", err)
		}
		sum.StartedAt = time.UnixMilli(startedAt)
		sum.Duration = time.Duration(durationMs) * time.Millisecond
		out = append(out, sum)
	}
	return out, rows.Err()
}

// Search returns up to limit history summaries older than beforeID (or
// the most recent if beforeID is 0) matching query, newest first among
// equally-ranked matches, best-relevance first otherwise. query is
// mostly plain text - "example.com", "x-forwarded-for", "192.168.1.1"
// all just work - plus a little FTS5 syntax for power users: AND/OR/NOT,
// and column filters like host:example.com. See prepareFTSQuery for why
// plain terms need help: FTS5's query grammar treats characters like
// '.', '-', '/', '@' as syntax, so an unquoted domain name is a parse
// error, not a search term, unless quoted first.
func (s *Store) Search(query string, limit int, beforeID int64) ([]Summary, error) {
	if limit <= 0 || limit > 1000 {
		limit = 200
	}
	if beforeID <= 0 {
		beforeID = 1<<63 - 1
	}
	query = prepareFTSQuery(query)
	// history_fts must appear unaliased for MATCH/bm25 to resolve against
	// it - this SQLite build doesn't support querying FTS5 through a
	// table alias (confirmed directly against the sqlite3 CLI: aliasing
	// it raises "no such column").
	rows, err := s.db.Query(
		`SELECT h.id, h.started_at, h.duration_ms, h.method, h.scheme, h.host, h.path,
		        COALESCE(h.status_code, 0), length(h.request_raw), COALESCE(length(h.response_raw), 0),
		        h.error, h.source
		 FROM history_fts
		 JOIN history h ON h.id = history_fts.rowid
		 WHERE history_fts MATCH ? AND h.id < ?
		 ORDER BY bm25(history_fts), h.id DESC LIMIT ?`,
		query, beforeID, limit,
	)
	if err != nil {
		return nil, fmt.Errorf("search history: %w", err)
	}
	defer rows.Close()

	var out []Summary
	for rows.Next() {
		var sum Summary
		var startedAt, durationMs int64
		if err := rows.Scan(&sum.ID, &startedAt, &durationMs, &sum.Method, &sum.Scheme, &sum.Host, &sum.Path,
			&sum.StatusCode, &sum.ReqSize, &sum.RespSize, &sum.Error, &sum.Source); err != nil {
			return nil, fmt.Errorf("scan search row: %w", err)
		}
		sum.StartedAt = time.UnixMilli(startedAt)
		sum.Duration = time.Duration(durationMs) * time.Millisecond
		out = append(out, sum)
	}
	return out, rows.Err()
}

// Get returns the full entry (including raw bytes) for id.
func (s *Store) Get(id int64) (*Entry, error) {
	row := s.db.QueryRow(
		`SELECT id, started_at, duration_ms, method, scheme, host, path,
		        COALESCE(status_code, 0), request_raw, response_raw,
		        request_exact, response_exact, error, source
		 FROM history WHERE id = ?`,
		id,
	)
	var e Entry
	var startedAt, durationMs int64
	var reqExact, respExact int
	if err := row.Scan(&e.ID, &startedAt, &durationMs, &e.Method, &e.Scheme, &e.Host, &e.Path,
		&e.StatusCode, &e.RequestRaw, &e.ResponseRaw, &reqExact, &respExact, &e.Error, &e.Source); err != nil {
		return nil, fmt.Errorf("get history entry %d: %w", id, err)
	}
	e.StartedAt = time.UnixMilli(startedAt)
	e.Duration = time.Duration(durationMs) * time.Millisecond
	e.RequestExact = reqExact != 0
	e.ResponseExact = respExact != 0
	return &e, nil
}

// prepareFTSQuery makes free text safe to hand to FTS5's MATCH, whose
// query grammar reserves a wide range of punctuation ('.', '-', '/',
// '@', '(', ')', and more - confirmed empirically, not just from docs)
// as syntax. A bareword containing any of it is a parse error, not a
// literal search term, which would make searching for the most common
// things in HTTP traffic (domains, paths, hyphenated headers, IPs) fail
// by default. So: quote every plain token as an FTS5 phrase, which is
// syntactically valid regardless of its contents, while still
// recognizing AND/OR/NOT and column:value filters for anyone using them
// deliberately.
//
// Known limitation: this splits on whitespace, so a query the user
// already wrote as a multi-word "quoted phrase" gets re-split and each
// word individually re-quoted (still a valid query, just no longer an
// exact-adjacency phrase match). Fine for the common case of typing
// plain, unquoted search terms, which is what this exists for.
func prepareFTSQuery(q string) string {
	fields := strings.Fields(q)
	for i, f := range fields {
		switch strings.ToUpper(f) {
		case "AND", "OR", "NOT":
			continue
		}
		if col, val, ok := strings.Cut(f, ":"); ok && col != "" && val != "" {
			fields[i] = col + `:"` + strings.ReplaceAll(val, `"`, `""`) + `"`
			continue
		}
		fields[i] = `"` + strings.ReplaceAll(f, `"`, `""`) + `"`
	}
	return strings.Join(fields, " ")
}

func boolToInt(b bool) int {
	if b {
		return 1
	}
	return 0
}