/*
 * Copyright 2010, Ingo Weinhold, ingo_weinhold@gmx.de.
 * Distributed under the terms of the MIT License.
 */


#include "pager.h"

#include <ctype.h>
#include <string.h>

#include <algorithm>

#include <boot/platform/generic/text_console.h>


// #pragma mark - PagerTextSource


PagerTextSource::~PagerTextSource()
{
}


// #pragma mark -


static size_t
next_line(const PagerTextSource& textSource, size_t width, size_t offset,
        char* buffer, size_t bufferSize)
{
        size_t bytesRead = textSource.Read(offset, buffer, bufferSize - 1);
        if (bytesRead == 0)
                return 0;

        buffer[bytesRead] = '\0';

        // replace all '\0's by spaces
        for (size_t i = 0; i < bytesRead; i++) {
                if (buffer[i] == '\0')
                        buffer[i] = ' ';
        }

        if (const char* lineEnd = strchr(buffer, '\n'))
                bytesRead = lineEnd - buffer;

        if (bytesRead > (size_t)width)
                bytesRead = width;

        // replace unprintables by '.'
        for (size_t i = 0; i < bytesRead; i++) {
                if (!isprint(buffer[i]))
                        buffer[i] = '.';
        }

        bool lineBreak = buffer[bytesRead] == '\n';

        buffer[bytesRead] = '\0';

        return bytesRead + (lineBreak ? 1 : 0);
}


static int32
count_lines(const PagerTextSource& textSource, size_t width, char* buffer,
        size_t bufferSize)
{
        int32 lineCount = 0;
        size_t offset = 0;

        while (true) {
                size_t bytesRead = next_line(textSource, width, offset, buffer,
                        bufferSize);
                if (bytesRead == 0)
                        break;

                offset += bytesRead;
                lineCount++;
        }

        return lineCount;
}


static size_t
offset_of_line(const PagerTextSource& textSource, size_t width, char* buffer,
        size_t bufferSize, int32 line)
{
        int32 lineCount = 0;
        size_t offset = 0;

        while (true) {
                if (line == lineCount)
                        return offset;

                size_t bytesRead = next_line(textSource, width, offset, buffer,
                        bufferSize);
                if (bytesRead == 0)
                        break;

                offset += bytesRead;
                lineCount++;
        }

        return offset;
}


// #pragma mark -


void
pager(const PagerTextSource& textSource)
{
        console_set_cursor(0, 0);

        int32 width = console_width();
        int32 height = console_height();

        char lineBuffer[256];

        int32 lineCount = count_lines(textSource, width, lineBuffer,
                sizeof(lineBuffer));
        int32 topLine = 0;

        bool quit = false;
        while (!quit) {
                // get the text offset for the top line
                size_t offset = offset_of_line(textSource, width, lineBuffer,
                        sizeof(lineBuffer), topLine);

                // clear the screen and print the lines
                console_clear_screen();

                int32 screenLine = 0;
                while (screenLine + 1 < height) {
                        size_t bytesRead = next_line(textSource, width, offset, lineBuffer,
                                sizeof(lineBuffer));
                        if (bytesRead == 0)
                                break;

                        console_set_cursor(0, screenLine);
                        puts(lineBuffer);

                        offset += bytesRead;
                        screenLine++;
                }

                // print the statistics line at the bottom
                console_set_cursor(0, height - 1);
                console_set_color(BLACK, GRAY);
                int32 bottomLine = std::min(topLine + height - 2, lineCount - 1);
                printf("%" B_PRId32 " - %" B_PRId32 "  %" B_PRId32 "%%",
                        topLine, bottomLine, (int32)((bottomLine + 1) * 100 / lineCount));
                console_set_color(WHITE, BLACK);

                // wait for a key that changes the position
                int32 previousTopLine = topLine;

                while (!quit && topLine == previousTopLine) {
                        switch (console_wait_for_key()) {
                                case TEXT_CONSOLE_KEY_ESCAPE:
                                case 'q':
                                case 'Q':
                                        // quit
                                        quit = true;
                                        break;

                                case TEXT_CONSOLE_KEY_DOWN:
                                case TEXT_CONSOLE_KEY_RETURN:
                                case 'j':
                                case 'J':
                                        // next line
                                        topLine++;
                                        break;

                                case TEXT_CONSOLE_KEY_UP:
                                case 'k':
                                case 'K':
                                        // previous line
                                        topLine--;
                                        break;

                                case TEXT_CONSOLE_KEY_PAGE_UP:
                                        // previous page
                                        topLine -= height - 1;
                                        break;

                                case TEXT_CONSOLE_KEY_PAGE_DOWN:
                                        // next page
                                        topLine += height - 1;
                                        break;

                                case TEXT_CONSOLE_KEY_HOME:
                                        // beginning of text
                                        topLine = 0;
                                        break;

                                case TEXT_CONSOLE_KEY_END:
                                        // end of text
                                        topLine = lineCount;
                                        break;
                        }

                        if (topLine > lineCount - (height - 1))
                                topLine = lineCount - (height - 1);
                        if (topLine < 0)
                                topLine = 0;
                }
        }
}