// SPDX-License-Identifier: GPL-3.0-or-later

package config

import (
	"fmt"
	"slices"
	"time"

	"git.labunix.xyz/krino/internal/sexp"
)

// CaseMode says whether name, path and content matching ignores case.
type CaseMode int

const (
	CaseIgnore CaseMode = iota
	CaseStrict
)

// Conflict is what to do when an action's target already exists.
type Conflict int

const (
	ConflictSuffix Conflict = iota
	ConflictSkip
	ConflictOverwrite
)

// String is the word a CaseMode is written as in a configuration.
func (m CaseMode) String() string {
	switch m {
	case CaseIgnore:
		return "ignore"
	case CaseStrict:
		return "strict"
	}
	return fmt.Sprintf("CaseMode(%d)", int(m))
}

// String is the word a Conflict policy is written as in a configuration.
func (c Conflict) String() string {
	switch c {
	case ConflictSuffix:
		return "suffix"
	case ConflictSkip:
		return "skip"
	case ConflictOverwrite:
		return "overwrite"
	}
	return fmt.Sprintf("Conflict(%d)", int(c))
}

// Settings holds what one level of config sets; nil means not set there.
type Settings struct {
	Case       *CaseMode
	Fold       *bool
	Recursive  *bool
	MaxDepth   *int
	MinAge     *time.Duration
	MaxRead    *int64
	MaxSize    *int64
	Busy       *[]string
	OnConflict *Conflict
}

// Resolved is a complete set of settings.
type Resolved struct {
	Case       CaseMode
	Fold       bool
	Recursive  bool
	MaxDepth   int // 0 means unlimited
	MinAge     time.Duration
	MaxRead    int64
	MaxSize    int64 // 0 means unlimited
	Busy       []string
	OnConflict Conflict
}

// Builtin is what applies when nothing is set.
func Builtin() Resolved {
	return Resolved{
		Case:       CaseIgnore,
		Fold:       true,
		MinAge:     2 * time.Minute,
		MaxRead:    50 << 20,
		Busy:       []string{".part", ".aria2", ".crdownload"},
		OnConflict: ConflictSuffix,
	}
}

// Over returns base with every setting that s sets replaced.
func (s Settings) Over(base Resolved) Resolved {
	r := base
	if s.Case != nil {
		r.Case = *s.Case
	}
	if s.Fold != nil {
		r.Fold = *s.Fold
	}
	if s.Recursive != nil {
		r.Recursive = *s.Recursive
	}
	if s.MaxDepth != nil {
		r.MaxDepth = *s.MaxDepth
	}
	if s.MinAge != nil {
		r.MinAge = *s.MinAge
	}
	if s.MaxRead != nil {
		r.MaxRead = *s.MaxRead
	}
	if s.MaxSize != nil {
		r.MaxSize = *s.MaxSize
	}
	if s.Busy != nil {
		r.Busy = *s.Busy
	}
	if s.OnConflict != nil {
		r.OnConflict = *s.OnConflict
	}
	return r
}

var settingNames = []string{"case", "fold", "recursive", "max-depth", "min-age", "max-read", "max-size", "busy", "on-conflict"}

// ruleSettings are the settings a rule may override.
var ruleSettings = map[string]bool{"case": true, "fold": true, "on-conflict": true}

func isSetting(name string) bool { return slices.Contains(settingNames, name) }

var settingHint = map[string]string{
	"case":        "(case ignore) or (case strict)",
	"fold":        "(fold yes) or (fold no)",
	"recursive":   "(recursive yes) or (recursive no)",
	"max-depth":   "a number, like (max-depth 3)",
	"min-age":     "a duration, like (min-age 2m)",
	"max-read":    "a size, like (max-read 50M)",
	"max-size":    "a size, like (max-size 1G)",
	"on-conflict": "(on-conflict suffix), skip or overwrite",
}

// parse reads the setting form n into s, reporting problems to d. seen
// catches a setting given twice at the same level.
func (s *Settings) parse(n *sexp.Node, d *diags, seen map[string]*sexp.Node) {
	name := n.Head()
	if first, ok := seen[name]; ok {
		d.at(n, "%s set twice (first at line %d)", name, first.Pos.Line)
		return
	}
	seen[name] = n
	args := n.Args()
	if name == "busy" {
		list := []string{}
		for _, a := range args {
			if a.Kind != sexp.String {
				d.at(a, `busy takes strings, like ".part"; got %s`, a)
				continue
			}
			list = append(list, a.Text)
		}
		s.Busy = &list
		return
	}
	if len(args) == 1 && args[0].Kind == sexp.String {
		d.at(args[0], "%s values are bare words: write (%s %s)", name, name, args[0].Text)
		return
	}
	if len(args) != 1 || args[0].Kind != sexp.Symbol {
		d.at(n, "%s takes one value: %s", name, settingHint[name])
		return
	}
	v, at := args[0].Text, args[0]
	switch name {
	case "case":
		switch v {
		case "ignore":
			c := CaseIgnore
			s.Case = &c
		case "strict":
			c := CaseStrict
			s.Case = &c
		default:
			d.at(at, "case is ignore or strict, not %s", v)
		}
	case "fold", "recursive":
		b, ok := yesNo(v)
		if !ok {
			d.at(at, "%s is yes or no, not %s", name, v)
		} else if name == "fold" {
			s.Fold = &b
		} else {
			s.Recursive = &b
		}
	case "max-depth":
		depth, err := parseCount(v)
		if err != nil || depth < 1 || depth > 1<<20 {
			d.at(at, "max-depth is a whole number from 1, not %s", v)
			return
		}
		i := int(depth)
		s.MaxDepth = &i
	case "min-age":
		dur, err := ParseDuration(v)
		if err != nil {
			d.at(at, "min-age: %v", err)
			return
		}
		s.MinAge = &dur
	case "max-read":
		size, err := ParseSize(v)
		if err != nil {
			d.at(at, "max-read: %v", err)
			return
		}
		s.MaxRead = &size
	case "max-size":
		size, err := ParseSize(v)
		if err != nil {
			d.at(at, "max-size: %v", err)
			return
		}
		s.MaxSize = &size
	case "on-conflict":
		c, ok := map[string]Conflict{"suffix": ConflictSuffix, "skip": ConflictSkip, "overwrite": ConflictOverwrite}[v]
		if !ok {
			d.at(at, "on-conflict is suffix, skip or overwrite, not %s", v)
			return
		}
		s.OnConflict = &c
	}
}

func yesNo(v string) (bool, bool) {
	switch v {
	case "yes":
		return true, true
	case "no":
		return false, true
	}
	return false, false
}