package cardsim

import (
	"fmt"
	"strings"
)

// An InfoPanel displays some set of stats to the player. It does
// not consume an action. It must not advance the state of the game
// in any way.
type InfoPanel[C StatsCollection] interface {
	// Title returns the title of this InfoPanel, which is also used as the
	// label presented to the player to access this panel.
	Title(p *Player[C]) (Message, error)

	// Info returns the displayable contents of this InfoPanel. A nil Message
	// in the output is interpreted as a paragraph break.
	Info(p *Player[C]) ([]Message, error)
}

// A StatFilter decides whether to show a specific stat in a BasicStatsPanel
// (and maybe other kinds of stats panels, if they choose to support this).
type StatFilter[C StatsCollection] func(p *Player[C], s Stat) bool

// BasicStatsPanel shows some or all of the stats output by C, under
// a fixed name, introduced by a specific prompt. Stats are shown as a two
// column table with the name, then the value.
type BasicStatsPanel[C StatsCollection] struct {
	// Name stores the name of this stats panel, which is also shown in the menu.
	Name Message

	// Intro stores a message to always display before the stats. Optional.
	Intro Message

	// Filter stores a function to decide what stats to show. If this is not
	// provided, the BasicStatsPanel uses VisibleOrDebug by default.
	Filter StatFilter[C]
}

// VisibleOrDebug returns whether s is Visible or p is in debug mode,
// so a debug-mode player shows all stats.
func VisibleOrDebug[C StatsCollection](p *Player[C], s Stat) bool {
	return p.DebugLevel > 0 || s.Visible()
}

// Title implements `InfoPanel[C]` by returning b's `Name`.
func (b *BasicStatsPanel[C]) Title(p *Player[C]) (Message, error) {
	return b.Name, nil
}

// Info implements `InfoPanel[C]` by dumpiing p.Stats, showing those items for
// whch b.Filter returns true.
func (b *BasicStatsPanel[C]) Info(p *Player[C]) ([]Message, error) {
	stats := p.Stats.Stats()
	cached := make([]cachedStat, 0, len(stats))
	longestName := 0
	filter := b.Filter
	if filter == nil {
		filter = VisibleOrDebug[C]
	}

	for _, s := range stats {
		if !filter(p, s) {
			continue
		}
		name := s.StatName()
		if len(name) > longestName {
			longestName = len(name)
		}
		cached = append(cached, cachedStat{name, s.String(), s.Visible()})
	}

	if len(cached) == 0 {
		return []Message{b.Intro, nil, MsgStr("No stats available")}, nil
	}

	ret := make([]Message, 0, 2+len(cached))
	ret = append(ret, b.Intro, nil)
	for _, s := range cached {
		ret = append(ret, MsgStr(s.output(longestName)))
	}
	return ret, nil
}

// cachedStat is an implementation detail of BasicStatsPanel.Info. It stores the
// values out of a stat so they do not need to be recalculated, in case they
// are expensive to calculate or the filter deciding which stats to output
// was expensive.
type cachedStat struct {
	name    string
	value   string
	visible bool
}

// output returns a string representing this stat, right-aligning the name in
// a nameWidth-wide field and prefixing it with a bullet: "•" for a visible
// stat and "◦" for an invisible stat. If nameWidth is 0, the name and
// colon are omitted. If it is negative, the name is emitted as-is with
// no alignment. If it is too short for the name and it is nonzero,
// it is truncated with "⋯".
func (c cachedStat) output(nameWidth int) string {
	bullet := "◦"
	if c.visible {
		bullet = "•"
	}

	if nameWidth == 0 {
		return fmt.Sprintf("%s %s", bullet, c.value)
	}

	name := c.name
	if len(name) < nameWidth {
		name = strings.Repeat(" ", nameWidth-len(name)) + name
	}
	if len(name) > nameWidth && nameWidth > 0 {
		name = name[:nameWidth-1] + "⋯"
	}

	return fmt.Sprintf("%s %s: %s", bullet, name, c.value)
}

// StatsNamed returns a StatFilter[C] matching any stat with a listed name.
func StatsNamed[C StatsCollection](names ...string) StatFilter[C] {
	nameSet := make(map[string]bool)
	for _, n := range names {
		nameSet[n] = true
	}
	return func(_ *Player[C], s Stat) bool {
		return nameSet[s.StatName()]
	}
}

// VisibleOrDebugStatsNamed returns a StatFilter[C] matching any visible stat
// with a listed name, or any stat with a listed name if the player is in
// debug mode.
func VisibleOrDebugStatsNamed[C StatsCollection](names ...string) StatFilter[C] {
	return All(VisibleOrDebug[C], StatsNamed[C](names...))
}

// All returns a StatFilter[C] that requires a Stat to match all provided
// filters. If no filters are provided, All matches every Stat (it's very easy
// to meet every requirement when there are no requirements).
func All[C StatsCollection](ff ...StatFilter[C]) StatFilter[C] {
	return func(p *Player[C], s Stat) bool {
		for _, f := range ff {
			if !f(p, s) {
				return false
			}
		}
		return true
	}
}

// Any returns a StatFilter[C] that requires a Stat to match any one or more of
// the filters provided. If no filters are provided, Any never matches a stat
// (it's very hard to meet at least one requirement out when there are no
// requirements).
func Any[C StatsCollection](ff ...StatFilter[C]) StatFilter[C] {
	return func(p *Player[C], s Stat) bool {
		for _, f := range ff {
			if f(p, s) {
				return true
			}
		}
		return false
	}
}