package commandkit

import (
	"bytes"
	"errors"
	"fmt"
	"strconv"
	"unicode"
)

func newConfigShowCommand[C any](prepared *preparedConfigSuite[C]) (Command, error) {
	spec := CommandSpec[configInput[C]]{
		Name:    string(ConfigShow),
		Summary: "Show effective configuration as YAML.",
		Flags:   configInputFlags(prepared.suite, "yaml"),
		CheckInput: func(input configInput[C]) error {
			_, err := preflightConfig(prepared, input, ConfigShow)
			return err
		},
		Run: func(invocation Invocation, input configInput[C]) Outcome {
			return runConfigShow(invocation, prepared, input)
		},
	}
	return NewCommand(spec)
}

type effectiveDocument struct {
	name string
	view ConfigView
}

func runConfigShow[C any](invocation Invocation, prepared *preparedConfigSuite[C], input configInput[C]) Outcome {
	if err := invocation.Context.Err(); err != nil {
		return Failure(err)
	}
	scopeNames, err := selectConfigScopes(prepared, input, ConfigShow)
	if err != nil {
		return Failure(err)
	}
	contexts := contextsForScopes(prepared, input, scopeNames)
	documents := make([]effectiveDocument, 0, len(scopeNames))
	diagnostics := make([]Diagnostic, 0)
	for _, name := range scopeNames {
		scope, ok := findConfigScope(prepared, name)
		if !ok || scope.Acquire == nil {
			return showFailure(fmt.Errorf("configuration scope %q has no acquisition callback", name), diagnostics, false)
		}
		if err := invocation.Context.Err(); err != nil {
			return showFailure(err, diagnostics, false)
		}
		acquired, acquireErr := scope.Acquire(invocation.Context, ConfigRequest{Operation: ConfigShow, Selection: input.Selection}, contexts[name])
		diagnostics = append(diagnostics, acquired.Diagnostics...)
		if acquireErr != nil {
			return showFailure(acquireErr, diagnostics, false)
		}
		if err := invocation.Context.Err(); err != nil {
			return showFailure(err, diagnostics, false)
		}

		if acquired.Value.Effective == nil {
			return showFailure(fmt.Errorf("configuration scope %q did not provide an effective configuration writer", name), diagnostics, false)
		}
		documents = append(documents, effectiveDocument{name: name, view: acquired.Value})
	}

	if err := invocation.Context.Err(); err != nil {
		return showFailure(err, diagnostics, false)
	}
	if len(documents) == 1 && input.Scope != "all" {
		checked := &checkedWriter{writer: invocation.Streams.Out}
		renderErr := documents[0].view.Effective.WriteEffective(checked)
		if checked.failure != nil {
			if renderErr == nil {
				renderErr = checked.failure
			} else {
				renderErr = errors.Join(renderErr, checked.failure)
			}
		}
		if renderErr != nil {
			outcome := showFailure(renderErr, diagnostics, true)
			outcome.DeliveryError = checked.failure
			return outcome
		}
		outcome := Success()
		outcome.Diagnostics = diagnostics
		return outcome
	}

	written := false
	for index, document := range documents {
		if err := invocation.Context.Err(); err != nil {
			return showFailure(err, diagnostics, written)
		}
		var native bytes.Buffer
		if err := document.view.Effective.WriteEffective(&native); err != nil {
			return showFailure(err, diagnostics, written)
		}
		if err := invocation.Context.Err(); err != nil {
			return showFailure(err, diagnostics, written)
		}
		framed, hasDirective := frameEffectiveYAML(document.name, native.Bytes())
		if index > 0 && hasDirective {
			if err := writeReport(invocation.Streams.Out, []byte("...\n")); err != nil {
				outcome := showFailure(err, diagnostics, true)
				outcome.DeliveryError = err
				return outcome
			}
		}
		if index < len(documents)-1 && len(framed) > 0 && framed[len(framed)-1] != '\n' {
			framed = append(framed, '\n')
		}
		if err := writeReport(invocation.Streams.Out, framed); err != nil {
			outcome := showFailure(err, diagnostics, true)
			outcome.DeliveryError = err
			return outcome
		}
		written = true
	}
	outcome := Success()
	outcome.Diagnostics = diagnostics
	return outcome
}

type yamlPreamble struct {
	markerStart  int
	markerEnd    int
	markerFound  bool
	inlineMarker bool
	preambleEnd  int
	hasDirective bool
}

func analyzeYAMLPreamble(native []byte) yamlPreamble {
	var analysis yamlPreamble
	for start := 0; start < len(native); {
		end := len(native)
		if newline := bytes.IndexByte(native[start:], '\n'); newline >= 0 {
			end = start + newline + 1
		}
		lineEnd := end
		if lineEnd > start && native[lineEnd-1] == '\n' {
			lineEnd--
		}
		trimmed := bytes.TrimSpace(native[start:lineEnd])
		if isYAMLDocumentStart(trimmed) {
			content := bytes.TrimSpace(trimmed[3:])
			analysis.markerStart = start
			analysis.markerEnd = end
			analysis.markerFound = true
			analysis.inlineMarker = len(content) > 0 && content[0] != '#'
			return analysis
		}
		if bytes.HasPrefix(trimmed, []byte("%YAML ")) || bytes.HasPrefix(trimmed, []byte("%TAG ")) {
			analysis.hasDirective = true
		}
		if len(trimmed) == 0 || trimmed[0] == '#' || bytes.HasPrefix(trimmed, []byte("%YAML ")) || bytes.HasPrefix(trimmed, []byte("%TAG ")) {
			analysis.preambleEnd = end
		} else {
			return analysis
		}
		start = end
	}
	return analysis
}

func frameEffectiveYAML(scope string, native []byte) ([]byte, bool) {
	analysis := analyzeYAMLPreamble(native)
	label := scope
	for _, r := range scope {
		if unicode.IsControl(r) {
			label = strconv.Quote(scope)
			break
		}
	}
	comment := []byte("# scope: " + label + "\n")
	if analysis.markerFound {
		out := make([]byte, 0, len(native)+len(comment))
		// Inline content may be a block scalar; place the label before
		// its marker rather than interrupting the native value.
		if analysis.inlineMarker {
			out = append(out, native[:analysis.markerStart]...)
			out = append(out, comment...)
			out = append(out, native[analysis.markerStart:]...)
			return out, analysis.hasDirective
		}
		out = append(out, native[:analysis.markerEnd]...)
		if analysis.markerEnd > analysis.markerStart && native[analysis.markerEnd-1] != '\n' {
			out = append(out, '\n')
		}
		out = append(out, comment...)
		out = append(out, native[analysis.markerEnd:]...)
		return out, analysis.hasDirective
	}
	result := make([]byte, 0, len(native)+len(comment)+5)
	if analysis.hasDirective {
		result = append(result, native[:analysis.preambleEnd]...)
	}
	result = append(result, []byte("---\n")...)
	result = append(result, comment...)
	if analysis.hasDirective {
		result = append(result, native[analysis.preambleEnd:]...)
	} else {
		result = append(result, native...)
	}
	return result, analysis.hasDirective
}

func showFailure(cause error, diagnostics []Diagnostic, reportStarted bool) Outcome {
	outcome := Failure(cause)
	outcome.Diagnostics = diagnostics
	outcome.ReportIncomplete = reportStarted
	return outcome
}

func isYAMLDocumentStart(line []byte) bool {
	return bytes.HasPrefix(line, []byte("---")) && (len(line) == 3 || line[3] == ' ' || line[3] == '\t')
}