package Torello.Browser;

import Torello.Java.ReadOnly.ReadOnlyList;
import Torello.Java.StringParse;
import Torello.Java.UnreachableError;

import java.util.function.IntFunction;

class ParamRec
{
    // ********************************************************************************************
    // ********************************************************************************************
    // Fields
    // ********************************************************************************************
    // ********************************************************************************************


    // Maximum width used when wrapping the generated diagnostic text.
    private static final int MAX_LINE_LINE = 100;

    // Accumulates the text generated during one complete toString pass.
    final StringBuilder sb = new StringBuilder();

    // The object currently being printed; either a BaseType<?> or an AbstractBuilder<?> subclass.
    final Object THIS;

    // Descriptor metadata for either class fields or command/type builder parameters.
    final AbstractDescriptor descriptor;


    // Retrieves an actual value using an index
    // BaseType         => value of a field (the 'ith' field)
    // CommandBuilders  => value assigned to a method parameter (the 'ith' parameter)
    // TypeBuilder      => value assigned to a field (the 'ith' field)

    final IntFunction<Object> getValue;


    // Number of descriptor entries:
    // BaseType         => number of fields,
    // CommandBuilders  => number of method parameters
    // TypeBuilder      => number of field-assignments

    final int NUM;


    // BaseType         => BaseType<Instance>.getClass()
    // CommandBuilders  => CommandBuilder.class
    // TypeBuilder      => TypeBuilder.class

    final Class<?> clazz;

    // Current indentation depth, normally increased in multiples of four spaces.
    final int CURRENT_INDENT;

    // Padding width used to align printed field or parameter names.
    final int NAME_PADDING;

    // Remaining first-line width passed to StrPrint.wrapToIndentationPlus().
    final int VAL_PRINT_LEN;

    // Line width available after current indentation.
    final int MAX_LINE_LEN;

    // Cached indentation string: StringParse.nChars(' ', CURRENT_INDENT).
    final String INDENT;


    // Header printed above this block:
    // BaseType input will print:       RunTime.ObjectPreview
    // TypeBuilder input will print:    TypeBuilder for RunTime.ObjectPreview
    // CommandBuilder input will print: CommandBuilder for RunTime.evaluate

    final String printedName;


    // ********************************************************************************************
    // ********************************************************************************************
    // Constructors
    // ********************************************************************************************
    // ********************************************************************************************


    ParamRec(final BaseType<?> bt)
    { this(bt, true, bt.getDescriptor(), 4); }

    ParamRec(final AbstractBuilder<?> ab)
    { this(ab, false, ab.descriptor, 4); }

    ParamRec(final BaseType<?> bt, final ParamRec rec)
    { this(bt, true, bt.getDescriptor(), rec.CURRENT_INDENT + 4); }

    private ParamRec(
            final Object                THIS,
            final boolean               baseType_OR_AbstractBuilder,
            final AbstractDescriptor    descriptor,
            final int                   CURRENT_INDENT
        )
    {
        this.THIS           = THIS;
        this.descriptor     = descriptor;
        this.NUM            = descriptor.names.size();
        this.clazz          = THIS.getClass();
        this.CURRENT_INDENT = CURRENT_INDENT;
        this.NAME_PADDING   = getMaxNameLen(descriptor.names);
        this.VAL_PRINT_LEN  = MAX_LINE_LINE - this.NAME_PADDING - CURRENT_INDENT;
        this.MAX_LINE_LEN   = MAX_LINE_LINE - CURRENT_INDENT;
        this.INDENT         = StringParse.nChars(' ', CURRENT_INDENT);


        // I spent at least 3 hours on this string stuff today.  These comments are essentialy
        // a summary of what I did today.  They are really good, though!  Thanks Chat-GPT!
        // 
        // "printedName" is the human-readable header shown at the top of the
        // generated diagnostic block.
        //
        // BaseType instances print using their nested CDP type name:
        //
        //     RunTime.ObjectPreview
        //
        // Builder instances print using:
        //
        //     TypeBuilder for RunTime.ObjectPreview
        //     CommandBuilder for RunTime.evaluate
        //
        // This distinction exists purely for diagnostics/debugging readability.

        this.printedName = baseType_OR_AbstractBuilder
            ? CDPToString.className(this.clazz)
            : THIS.getClass().getSimpleName() + " for " + descriptor.domain + "." + descriptor.name;


        // The "getValue" function-pointer abstracts the only meaningful behavioral
        // difference between:
        //
        //     BaseType<?>
        //     AbstractBuilder<?>
        //
        // BaseType values are retrieved reflectively from public fields.
        //
        // Builder values are retrieved directly from the internal assignments[] array.
        //
        // The remainder of the formatting pipeline is identical for both pathways.

        this.getValue = baseType_OR_AbstractBuilder
            ? this::getValueBaseType
            : this::getValueAbstractDescriptor;
    }


    // ********************************************************************************************
    // ********************************************************************************************
    // Helper
    // ********************************************************************************************
    // ********************************************************************************************


    private Object getValueBaseType(final int i)
    {
        try
            { return this.clazz.getField(this.descriptor.names.get(i)).get(this.THIS); }

        catch (NoSuchFieldException e)
            { throw new UnreachableError(); }

        catch (IllegalAccessException e)
            { throw new UnreachableError(); }
    }

    @SuppressWarnings("unchecked")
    private Object getValueAbstractDescriptor(final int i)
    { return ((AbstractBuilder) this.THIS).assignments[i]; }

    private static int getMaxNameLen(final ReadOnlyList<String> names)
    {
        int maxNameLen  = 0;

        for (final String name : names)
            if (name.length() > maxNameLen)
                maxNameLen = name.length();

        return maxNameLen + 2; // ": ".length() => 2
    }

}