package store

import (
	"database/sql"
	"fmt"
	"strconv"
	"strings"
)

// Series filter names (issue #140): the seven repair filters are ordered
// permanent-then-fixable — the repairs nothing will ever undo first, the
// ones a Poll can make right after. SeriesFilterFinished is not part of
// that ordering: a finished Series is a deliberate state, not a repair, so
// it sits last, informational. A name is the repair a row needs, not the
// SQL that finds it; the values are the wire form the Series list URL
// carries (#142). "all" is the absent and unknown case: every Series.
const (
	SeriesFilterAll          = "all"
	SeriesFilterNoURL        = "no_series_url"
	SeriesFilterNoChapter    = "never_read_a_chapter"
	SeriesFilterNoReaders    = "no_readers"
	SeriesFilterNeverChecked = "never_checked"
	SeriesFilterStale        = "stale"
	SeriesFilterNoCover      = "no_cover"
	SeriesFilterReaderReport = "reader_report"
	SeriesFilterFinished     = "finished"
	SeriesFilterFailing      = "failing"
	SeriesFilterUnverified   = "unverified"
)

// SeriesFilter is one named filter predicate over the whole library. Site
// and Kind narrow the row read; Name picks the predicate; Cutoff is the
// staleness boundary the age-based filters — "stale" and the failing pair —
// compare against, supplied by the caller's clock — the store has no clock;
// Page is 1-based.
type SeriesFilter struct {
	Site   string // "" = every Site
	Kind   string // "" = both library buckets' series
	Name   string // one of the SeriesFilter* constants; "" = SeriesFilterAll
	Cutoff int64  // unix ms; the age-based filters read it, the store never does
	Page   int    // 1-based page of the row read; default 1
}

// adminSeriesColumns is the owner's library-wide Series projection in
// scanAdminSeries order. It is the privacy boundary: a Series' row carries
// the Reader id that raised its Latest Chapter (latest_raised_by), and that id
// must never leave the store package — so the projection does not select it,
// and only the anonymous boolean in raisedByReaderAnswer crosses it.
const adminSeriesColumns = `s.site, s.series_id, s.title, s.series_url, s.cover_address,
	s.kind, s.latest_chapter, s.latest_chapter_num, s.latest_checked_at, s.force_poll_at,
	s.latest_corrected_at, s.finished_at`

// raisedByReaderAnswer answers "did a Reader's report set this number" without
// naming which Reader. Kept apart from adminSeriesColumns so the column list —
// the shape scanAdminSeries is fed — stays free of the Sighting-raiser
// identity, and the owner learns which rows to act on and nothing about the
// Reader behind them.
const raisedByReaderAnswer = `(s.latest_raised_by IS NOT NULL) AS raised_by_reader`

// failureAnswer is the poll-failures row's answer (issue #165), kept apart
// from adminSeriesColumns like raisedByReaderAnswer: outcome and failing_since
// are not Series columns, and the COALESCE keeps the row scannable when the
// LEFT JOIN finds no failure row.
const failureAnswer = `COALESCE(f.outcome, ''), COALESCE(f.failing_since, 0)`

// seriesPageSize is the row read's page length. The tie-break in the query's
// ORDER BY is what makes this a stable page boundary — see SeriesPage.
const seriesPageSize = 50

// AdminSeries is one Series as the owner's library-wide view sees it: a
// Series-level fact plus an anonymous Reader count. ReaderCount being zero is
// the orphan marker. RaisedByReader is the only trace of the Sighting
// mechanism here; the Reader id behind it never reaches this type.
type AdminSeries struct {
	Site             string
	SeriesID         string
	Title            string
	SeriesURL        string
	CoverAddress     string // "" = no Cover yet
	Kind             string
	LatestChapter    string
	LatestChapterNum *float64 // nil until first captured
	LatestCheckedAt  int64
	// ForcePollAt is the owner's "check now" request stamp (issue #146), zero
	// meaning never asked. Pending is derived, never stored: a request is
	// pending while ForcePollAt is newer than LatestCheckedAt.
	ForcePollAt int64
	// LatestCorrectedAt is the correction stamp (issue #149): non-zero means
	// the Latest Chapter is the owner's, zero means never corrected. The
	// provenance line (#152) derives from it, so the zero-means-never meaning
	// is load-bearing.
	LatestCorrectedAt int64
	ReaderCount       int
	RaisedByReader    bool // a Reader's report set LatestChapterNum
	// FailureOutcome is the outcome word of the Series' standing failure, ""
	// when no failure row stands. FailingSince is when the run of failures
	// began, zero with no row. Both come from the LEFT JOIN, not the Series
	// row (issue #165: the row's existence is the state).
	FailureOutcome string
	FailingSince   int64
	// FinishedAt is the owner's finish stamp: unix ms, zero while the Series is
	// not finished — the same shape as the Correction stamp, and its own undo.
	FinishedAt int64
}

// SeriesPage is one page of the owner's filtered Series list plus the count
// of every Series matching the same filter — a window number, not the page's
// len, so the landing page's figure and the list heading come from one query.
type SeriesPage struct {
	Rows  []AdminSeries
	Total int
}

// SiteSeriesShape is one Site's share of the Series matching a filter: how
// many, and the manga/novel split. One grouped pass, then library-wide totals
// are summed in Go over the rows — the landing page's per-Site table reads
// this and never pays for the rows the list discards.
type SiteSeriesShape struct {
	Site  string
	Total int
	Manga int
	Novel int
}

// Key returns the canonical identity in bookmark-key form ("<site>:<series_id>").
func (a AdminSeries) Key() string { return a.Site + ":" + a.SeriesID }

// adminFilter maps a filter's named predicate to its compile-time WHERE and
// HAVING clauses and their bound parameters — the name never reaches query
// text, and Site and Kind bind as parameters. Shared by the row read and the
// per-Site aggregate so the two cannot disagree on what a filter means.
//
// The WHERE set is: no URL (an empty URL only — the host-failing-the-fetch-
// gate case is invisible to SQL, needs the Site registry in Go, and belongs to
// a later repair), never-read-a-chapter and never-checked as disjoint halves
// (non-zero versus zero check stamp), stale, no cover, finished (the
// retirement stamp, read directly), Reader-report, and the failing pair —
// failing (the failure row exists, a chapter exists, and failing_since is
// past the cutoff) and unverified (the Reader-attributed subset of failing).
// failing's chapter IS NOT NULL is the exact complement of never-read-a-
// chapter's IS NULL half, so the two are disjoint by construction.
// no_readers is the one HAVING predicate: it is the orphan test, an aggregate
// over the LEFT JOIN, where a bare WHERE has no row to test.
//
// The clock-versus-outcome split decides which predicates exclude finished
// Series (`s.finished_at = 0` in each of the four): the clock-driven one —
// never-checked, stale, no-chapter, no-cover — keep ticking after the last
// Poll, so they would report a retired row as a problem no Poll is coming to
// fix; the outcome-driven ones — no-URL, no-readers, Reader-report, failing,
// unverified — read stored facts that simply stop arriving, so a finished
// Series needing a genuine repair still shows up under them. The failing pair
// carries no finished guard for exactly that contrast: a failure row is a
// stored outcome, not a ticking clock.
//
// stale is the checked-but-old half of the stamp partition — because the
// verdict line wants "not checked in twelve hours" as one figure, and a never
// checked Series is already counted on its own "waiting"/never-checked
// filter, folding it in would double-report it. The landing page computes the
// inclusive number as stale + never-checked.
func adminFilter(f SeriesFilter) (where, having string, args []any, err error) {
	var clauses []string
	if f.Kind != "" {
		args = append(args, f.Kind)
		clauses = append(clauses, "s.kind = $"+strconv.Itoa(len(args)))
	}
	switch f.Name {
	case "", SeriesFilterAll:
	case SeriesFilterNoURL:
		clauses = append(clauses, `s.series_url = ''`)
	case SeriesFilterNoChapter:
		clauses = append(clauses, `s.latest_checked_at <> 0 AND s.latest_chapter_num IS NULL AND s.finished_at = 0`)
	case SeriesFilterNeverChecked:
		clauses = append(clauses, `s.latest_checked_at = 0 AND s.finished_at = 0`)
	case SeriesFilterStale:
		clauses = append(clauses, `s.latest_checked_at > 0 AND s.latest_checked_at < $`+strconv.Itoa(len(args)+1)+` AND s.finished_at = 0`)
		args = append(args, f.Cutoff)
	case SeriesFilterNoCover:
		clauses = append(clauses, `s.cover_address = '' AND s.finished_at = 0`)
	case SeriesFilterReaderReport:
		clauses = append(clauses, `s.latest_raised_by IS NOT NULL`)
	case SeriesFilterFailing:
		clauses = append(clauses, `f.site IS NOT NULL AND s.latest_chapter_num IS NOT NULL AND f.failing_since < $`+strconv.Itoa(len(args)+1))
		args = append(args, f.Cutoff)
	case SeriesFilterUnverified:
		clauses = append(clauses, `f.site IS NOT NULL AND s.latest_chapter_num IS NOT NULL AND f.failing_since < $`+strconv.Itoa(len(args)+1)+` AND s.latest_raised_by IS NOT NULL`)
		args = append(args, f.Cutoff)
	case SeriesFilterFinished:
		clauses = append(clauses, `s.finished_at > 0`)
	case SeriesFilterNoReaders:
		having = `HAVING COUNT(b.reader_id) = 0`
	default:
		return "", "", nil, fmt.Errorf("unknown series filter %q", f.Name)
	}
	if len(clauses) > 0 {
		where = "WHERE " + strings.Join(clauses, " AND ")
	}
	return where, having, args, nil
}

// SeriesPage returns one page of the Series matching the filter, least
// recently checked first. The LEFT JOIN to Bookmarks is what surfaces the
// orphans that hygiene has to find — an inner join would hide them, exactly
// as the Lane's join does. Every bookmark keeps its Series polled now that
// finished is a Series flag, so this plain ReaderCount agrees with the Lane
// queries (issue #157).
//
// The tie-break is mandatory, not decorative: every unpollable Series shares a
// zero check stamp, so ordering on that column alone gives no stable page
// boundary and rows would repeat or vanish across pages. (site, series_id) is
// the primary key, hence total. The filtered total is a window count in the
// same query — window functions run after grouping and before the limit, so
// one where-clause cannot disagree with a second copy of itself.
func (s *Store) SeriesPage(f SeriesFilter) (SeriesPage, error) {
	where, having, args, err := adminFilter(f)
	if err != nil {
		return SeriesPage{}, err
	}
	if f.Page < 1 {
		f.Page = 1
	}
	// Site narrowing is the row read's own; the aggregate must see every Site.
	if f.Site != "" {
		args = append(args, f.Site)
		clause := "s.site = $" + strconv.Itoa(len(args))
		if where == "" {
			where = "WHERE " + clause
		} else {
			where += " AND " + clause
		}
	}
	base := len(args)
	args = append(args, seriesPageSize, seriesPageSize*(f.Page-1))
	rows, err := s.db.Query(`
		SELECT `+adminSeriesColumns+`, `+raisedByReaderAnswer+`, `+failureAnswer+`,
		       COUNT(b.reader_id) AS reader_count,
		       COUNT(*) OVER () AS filtered_total
		FROM series s
		LEFT JOIN bookmarks b ON b.site = s.site AND b.series_id = s.series_id
		LEFT JOIN poll_failures f ON f.site = s.site AND f.series_id = s.series_id
		`+where+`
		GROUP BY s.site, s.series_id, s.title, s.series_url, s.cover_address,
		         s.kind, s.latest_chapter, s.latest_chapter_num, s.latest_checked_at,
		         s.force_poll_at, s.latest_corrected_at, s.finished_at, s.latest_raised_by,
		         f.outcome, f.failing_since
		`+having+`
		ORDER BY s.latest_checked_at, s.site, s.series_id
		LIMIT $`+strconv.Itoa(base+1)+` OFFSET $`+strconv.Itoa(base+2), args...)
	if err != nil {
		return SeriesPage{}, fmt.Errorf("query series page: %w", err)
	}
	defer rows.Close()

	out := SeriesPage{}
	for rows.Next() {
		a, total, err := scanAdminSeries(rows.Scan)
		if err != nil {
			return SeriesPage{}, fmt.Errorf("scan series page: %w", err)
		}
		out.Rows = append(out.Rows, a)
		out.Total = total
	}
	return out, rows.Err()
}

// SeriesShapes returns each Site's share of the Series matching the filter,
// one grouped pass. Site and Page are row-read concerns and are ignored; the
// Landing page reads this per Site and sums the totals in Go for the
// library-wide figure.
func (s *Store) SeriesShapes(f SeriesFilter) ([]SiteSeriesShape, error) {
	where, having, args, err := adminFilter(f)
	if err != nil {
		return nil, err
	}
	rows, err := s.db.Query(`
		SELECT site,
		       COUNT(*) AS total,
		       COUNT(*) FILTER (WHERE kind = 'manga') AS manga,
		       COUNT(*) FILTER (WHERE kind = 'novel') AS novel
		FROM (
			SELECT s.site, s.kind
			FROM series s
			LEFT JOIN bookmarks b ON b.site = s.site AND b.series_id = s.series_id
			LEFT JOIN poll_failures f ON f.site = s.site AND f.series_id = s.series_id
			`+where+`
			GROUP BY s.site, s.series_id, s.kind
			`+having+`
		) shape
		GROUP BY site
		ORDER BY site`, args...)
	if err != nil {
		return nil, fmt.Errorf("query series shapes: %w", err)
	}
	defer rows.Close()

	out := []SiteSeriesShape{}
	for rows.Next() {
		var sh SiteSeriesShape
		if err := rows.Scan(&sh.Site, &sh.Total, &sh.Manga, &sh.Novel); err != nil {
			return nil, fmt.Errorf("scan series shape: %w", err)
		}
		out = append(out, sh)
	}
	return out, rows.Err()
}

// scanAdminSeries reads one row in adminSeriesColumns + raisedByReaderAnswer +
// failureAnswer order, plus the query's reader_count and filtered_total
// columns, and returns the window total alongside the row. latest_chapter_num
// is NULL until first captured — the "never read a chapter" state. The
// Sighting-raiser column is never among the scanned columns.
func scanAdminSeries(scan func(...any) error) (AdminSeries, int, error) {
	var (
		a                AdminSeries
		latestChapterNum sql.NullFloat64
		total            int
	)
	if err := scan(
		&a.Site, &a.SeriesID, &a.Title, &a.SeriesURL, &a.CoverAddress,
		&a.Kind, &a.LatestChapter, &latestChapterNum, &a.LatestCheckedAt,
		&a.ForcePollAt, &a.LatestCorrectedAt, &a.FinishedAt,
		&a.RaisedByReader, &a.FailureOutcome, &a.FailingSince, &a.ReaderCount, &total,
	); err != nil {
		return AdminSeries{}, 0, err
	}
	if latestChapterNum.Valid {
		a.LatestChapterNum = &latestChapterNum.Float64
	}
	return a, total, nil
}