package db

import (
	"context"
	"fmt"
	"sort"
)

// Groups of a RegistryBreakdown: egress checks are grouped by target, ingress
// ones by prober site.
const (
	BreakdownTarget = "target"
	BreakdownSite   = "site"
)

// BreakdownRow is one group of a RegistryBreakdown: Key is the checks.target
// (egress) or the checks.source (ingress, "inbound-site-N"), Total the checks
// recorded for it and OK the successful ones.
type BreakdownRow struct {
	Key   string
	Total int
	OK    int
}

// Breakdown counts the checks of one direction and protocol per target or site.
type Breakdown struct {
	Group     string // BreakdownTarget or BreakdownSite
	Addresses int    // addresses of the filter, the same as ListRegistryPage's total
	Rows      []BreakdownRow
}

// breakdownChecks is `FROM … JOIN checks c … WHERE …` over the checks of the
// addresses f selects (registryFilterSQL), in the slice of f: the address's cycle
// in the run or its newest one, narrowed by Level and Family, which must be
// set. It also returns the column the checks are grouped by. CROSS JOIN keeps
// the checks as the inner table, so the addresses drive the lookups over the
// checks indexes whatever the table statistics say.
func (d *DB) breakdownChecks(ctx context.Context, f RegistryFilter) (q, group string, args []any, err error) {
	sl := registrySlice{RunID: f.RunID, Level: f.Level, Family: f.Family}
	if err := sl.validate(); err != nil {
		return "", "", nil, err
	}
	if sl.Level == "" || sl.Family == "" {
		return "", "", nil, fmt.Errorf("direction and protocol are required: %w", ErrValidation)
	}
	from, cond, args, err := d.registryFilterSQL(ctx, f, sl)
	if err != nil {
		return "", "", nil, err
	}
	group = "c.target"
	if sl.Level == LevelIngress {
		group = "c.source"
	}
	sc, scArgs := sl.scopeCond()
	q = from + `CROSS JOIN checks c ON c.registry_id = r.id AND c.cycle_id = `
	if sl.RunID > 0 {
		q += `rr.cycle_id WHERE ` + cond + ` AND c.run_id = ? AND ` + sc
		args = append(args, sl.RunID)
	} else {
		q += `(SELECT MAX(c2.cycle_id) FROM checks c2 WHERE c2.registry_id = r.id) WHERE ` + cond + ` AND ` + sc
	}
	return q, group, append(args, scArgs...), nil
}

// RegistryBreakdown counts the recorded checks of f.Level and f.Family (both
// required, else ErrValidation) per target (egress) or site (ingress), over
// the same slice and the same addresses — all under the filter, not one page —
// as ListRegistryPage. Rows are sorted by successful checks, most first, then by
// key. It counts checks, not addresses: an address can have several checks per
// site (tcp-22 and tcp-443).
func (d *DB) RegistryBreakdown(ctx context.Context, f RegistryFilter) (*Breakdown, error) {
	from, group, args, err := d.breakdownChecks(ctx, f)
	if err != nil {
		return nil, err
	}
	b := &Breakdown{Group: BreakdownTarget}
	if f.Level == LevelIngress {
		b.Group = BreakdownSite
	}
	rows, err := d.QueryContext(ctx, `SELECT `+group+`, COUNT(*), COALESCE(SUM(c.success), 0) `+from+` GROUP BY `+group, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	for rows.Next() {
		var r BreakdownRow
		if err := rows.Scan(&r.Key, &r.Total, &r.OK); err != nil {
			return nil, err
		}
		b.Rows = append(b.Rows, r)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}
	sort.Slice(b.Rows, func(i, j int) bool {
		if b.Rows[i].OK != b.Rows[j].OK {
			return b.Rows[i].OK > b.Rows[j].OK
		}
		return b.Rows[i].Key < b.Rows[j].Key
	})

	// The addresses of the filter, as ListRegistryPage counts them.
	sl := registrySlice{RunID: f.RunID, Level: f.Level, Family: f.Family}
	afrom, cond, aargs, err := d.registryFilterSQL(ctx, f, sl)
	if err != nil {
		return nil, err
	}
	if err := d.QueryRowContext(ctx, `SELECT COUNT(*)`+afrom+`WHERE `+cond, aargs...).Scan(&b.Addresses); err != nil {
		return nil, err
	}
	return b, nil
}

// RegistryBreakdownList returns the checks behind one row of RegistryBreakdown:
// those whose target (egress) or source (ingress) is key, with the address
// (IPAddress), type, validator, latency, detail and time, failures first, then
// by registry order. A key without checks is ErrNotFound.
func (d *DB) RegistryBreakdownList(ctx context.Context, f RegistryFilter, key string) ([]Check, error) {
	from, group, args, err := d.breakdownChecks(ctx, f)
	if err != nil {
		return nil, err
	}
	rows, err := d.QueryContext(ctx, `
		SELECT r.ip_address, c.validator_id, c.source, c.check_type, c.target, c.success, c.latency_ms, c.detail, c.checked_at `+
		from+` AND `+group+` = ? ORDER BY c.success, r.first_seen_at, r.id, c.check_type, c.source, c.target`, append(args, key)...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var out []Check
	for rows.Next() {
		var c Check
		var checkedAt string
		if err := rows.Scan(&c.IPAddress, &c.ValidatorID, &c.Source, &c.CheckType, &c.Target, &c.Success, &c.LatencyMS, &c.Detail, &checkedAt); err != nil {
			return nil, err
		}
		if c.CheckedAt, err = dbToTime(checkedAt); err != nil {
			return nil, err
		}
		out = append(out, c)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}
	if len(out) == 0 {
		return nil, fmt.Errorf("breakdown key %q: %w", key, ErrNotFound)
	}
	return out, nil
}