package diary

import (
	"context"
	"fmt"
	"io"
	"log/slog"
	"path/filepath"
	"runtime"
	"strconv"
	"strings"
	"sync"
	"sync/atomic"
	"time"
	"unicode"

	"git.golem15.com/golem15/summercms/modules/bonfire"
	"charm.land/lipgloss/v2"
	"github.com/charmbracelet/colorprofile"
)

// componentWidth is the column width of the component prefix.
const componentWidth = 10

// ConsoleOptions configures NewConsoleHandler.
type ConsoleOptions struct {
	// Level is the minimum level; nil means info.
	Level slog.Leveler
	// Profile is the color profile applied to the output; NoTTY writes no
	// escape codes at all.
	Profile colorprofile.Profile
	// AddSource appends the caller's file:line to each line.
	AddSource bool
}

// NewConsoleHandler returns a slog.Handler that writes one styled line per
// record to w in bonfire's palette: time, level, the component attribute as
// a fixed-width prefix, the message, then key=value attributes with groups
// as dotted key prefixes. Control characters other than tab are removed from
// the message and attribute values, so logged data cannot inject terminal
// escape sequences. Each line is written with one Write call, serialized
// across the handler and its WithAttrs and WithGroup clones.
func NewConsoleHandler(w io.Writer, opts ConsoleOptions) slog.Handler {
	source := new(atomic.Bool)
	source.Store(opts.AddSource)
	return newConsoleHandler(w, opts, source)
}

func newConsoleHandler(w io.Writer, opts ConsoleOptions, source *atomic.Bool) *consoleHandler {
	level := opts.Level
	if level == nil {
		level = slog.LevelInfo
	}
	return &consoleHandler{
		out:     &colorprofile.Writer{Forward: w, Profile: opts.Profile},
		mu:      new(sync.Mutex),
		level:   level,
		source:  source,
		palette: bonfire.DefaultPalette(),
	}
}

type consoleAttr struct {
	key   string
	value string
}

type consoleHandler struct {
	out       io.Writer
	mu        *sync.Mutex
	level     slog.Leveler
	source    *atomic.Bool
	palette   bonfire.Palette
	component string
	attrs     []consoleAttr
	groups    []string
}

func (h *consoleHandler) Enabled(_ context.Context, l slog.Level) bool {
	return l >= h.level.Level()
}

func (h *consoleHandler) clone() *consoleHandler {
	c := *h
	c.attrs = h.attrs[:len(h.attrs):len(h.attrs)]
	c.groups = h.groups[:len(h.groups):len(h.groups)]
	return &c
}

func (h *consoleHandler) WithAttrs(attrs []slog.Attr) slog.Handler {
	if len(attrs) == 0 {
		return h
	}
	c := h.clone()
	prefix := groupPrefix(c.groups)
	for _, a := range attrs {
		if len(c.groups) == 0 && a.Key == ComponentKey && a.Value.Kind() == slog.KindString {
			c.component = a.Value.String()
			continue
		}
		c.attrs = appendAttr(c.attrs, prefix, a)
	}
	return c
}

func (h *consoleHandler) WithGroup(name string) slog.Handler {
	if name == "" {
		return h
	}
	c := h.clone()
	c.groups = append(c.groups, name)
	return c
}

func (h *consoleHandler) Handle(_ context.Context, r slog.Record) error {
	component := h.component
	prefix := groupPrefix(h.groups)
	var recAttrs []consoleAttr
	r.Attrs(func(a slog.Attr) bool {
		if len(h.groups) == 0 && a.Key == ComponentKey && a.Value.Kind() == slog.KindString {
			component = a.Value.String()
			return true
		}
		recAttrs = appendAttr(recAttrs, prefix, a)
		return true
	})

	p := h.palette
	var b strings.Builder
	if !r.Time.IsZero() {
		b.WriteString(p.Muted.Render(r.Time.Format(time.TimeOnly)))
		b.WriteByte(' ')
	}
	label, style := levelLabel(r.Level, p)
	b.WriteString(style.Render(label))
	b.WriteString(strings.Repeat(" ", max(0, 5-len(label))+1))
	name := sanitize(component)
	if name != "" {
		b.WriteString(p.Header.Render(name))
	}
	b.WriteString(strings.Repeat(" ", max(0, componentWidth-len(name))+1))
	b.WriteString(sanitize(r.Message))
	for _, list := range [][]consoleAttr{h.attrs, recAttrs} {
		for _, a := range list {
			b.WriteByte(' ')
			b.WriteString(p.Muted.Render(a.key + "="))
			b.WriteString(a.value)
		}
	}
	if h.source != nil && h.source.Load() && r.PC != 0 {
		frame, _ := runtime.CallersFrames([]uintptr{r.PC}).Next()
		if frame.File != "" {
			b.WriteByte(' ')
			b.WriteString(p.Muted.Render(filepath.Base(frame.File) + ":" + strconv.Itoa(frame.Line)))
		}
	}
	b.WriteByte('\n')

	h.mu.Lock()
	defer h.mu.Unlock()
	_, err := io.WriteString(h.out, b.String())
	return err
}

func levelLabel(l slog.Level, p bonfire.Palette) (string, lipgloss.Style) {
	switch {
	case l < slog.LevelInfo:
		return l.String(), p.Muted
	case l < slog.LevelWarn:
		return l.String(), p.Current
	case l < slog.LevelError:
		return l.String(), p.Warning
	default:
		return l.String(), p.ErrorBold
	}
}

func groupPrefix(groups []string) string {
	if len(groups) == 0 {
		return ""
	}
	return strings.Join(groups, ".") + "."
}

// appendAttr flattens a into key=value pairs: empty attributes are skipped,
// groups add their key as a dotted prefix, and groups with an empty key are
// inlined (testing/slogtest semantics).
func appendAttr(out []consoleAttr, prefix string, a slog.Attr) []consoleAttr {
	a.Value = a.Value.Resolve()
	if a.Equal(slog.Attr{}) {
		return out
	}
	if a.Value.Kind() == slog.KindGroup {
		group := a.Value.Group()
		if len(group) == 0 {
			return out
		}
		inner := prefix
		if a.Key != "" {
			inner = prefix + a.Key + "."
		}
		for _, g := range group {
			out = appendAttr(out, inner, g)
		}
		return out
	}
	return append(out, consoleAttr{key: sanitize(prefix + a.Key), value: formatValue(a.Value)})
}

func formatValue(v slog.Value) string {
	var s string
	switch v.Kind() {
	case slog.KindString:
		s = v.String()
	case slog.KindTime:
		s = v.Time().Format(time.RFC3339)
	case slog.KindAny:
		if err, ok := v.Any().(error); ok {
			s = err.Error()
		} else {
			s = fmt.Sprintf("%+v", v.Any())
		}
	default:
		s = v.String()
	}
	s = sanitize(s)
	if s == "" || strings.ContainsAny(s, " \t\"=") {
		return strconv.Quote(s)
	}
	return s
}

// sanitize removes control characters other than tab; line breaks become
// spaces so a multi-line value stays on one line.
func sanitize(s string) string {
	clean := true
	for _, r := range s {
		if r != '\t' && unicode.IsControl(r) {
			clean = false
			break
		}
	}
	if clean {
		return s
	}
	var b strings.Builder
	for _, r := range s {
		switch {
		case r == '\n' || r == '\r':
			b.WriteByte(' ')
		case r != '\t' && unicode.IsControl(r):
		default:
			b.WriteRune(r)
		}
	}
	return b.String()
}