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/* Copyright (C) 2023 Purism SPC
 * SPDX-License-Identifier: LGPL-2.1-or-later
 */

/*! Configuration management.

Fill in Select with fixed values.

Call camera::which(Select, Param) and get a list of possibilities for the chosen Param. Repeat until satisfied.
Choose one, and call camera::select(Select) to get a set of matching configs.
Choose one, and use it to configure the camera.

`which` can be used to fix config parameters one by one. `select` fills in all remaining parameters, but may not give an exhaustive list of possibilities.
*/

use std::collections::HashSet;

type Resolution = (u32, u32);
#[derive(PartialEq, Eq, Clone, Copy, Hash, Debug)]
enum PixelFormat {
    Bayer,
    RGB,
}

#[derive(Clone, Hash, Debug, PartialEq, Eq)]
struct Config {
    resolution: Resolution,
    pixel_format: PixelFormat,
}

#[derive(Clone, Hash, Debug, PartialEq, Eq)]
struct Select {
    resolution: Option<Resolution>,
    pixel_format: Option<PixelFormat>,
}

enum Param {
    Resolution,
    PixelFormat,
}


#[derive(PartialEq)]
struct Response {
    resolution: Vec<Resolution>,
}

#[cfg(test)]
mod test {
    use super::*;
    
    const OPTIONS: &[(Resolution, PixelFormat)] = &[
        ((640, 480), PixelFormat::Bayer),
        ((640, 480), PixelFormat::RGB),
        ((1024, 480), PixelFormat::Bayer),
    ];
    
    fn check<T: PartialEq>(fix: &Option<T>, known: &T) -> bool {
        fix.as_ref().map(|f| f == known).unwrap_or(true)
    }

    fn select(fixed: Select) -> HashSet<Config> {
        OPTIONS.iter()
            .filter(|(r, pf)| {
                check(&fixed.resolution, r)
                && check(&fixed.pixel_format, pf)
            })
            .map(|(r, pf)| Config {
                resolution: *r,
                pixel_format: *pf,
            })
            .collect::<HashSet<_>>()
    }
    
    fn which(fixed: Select, wanted: Param) -> HashSet<Select> {
        let matching = OPTIONS.iter()
            .filter(|(r, pf)| {
                check(&fixed.resolution, r)
                && check(&fixed.pixel_format, pf)
            });
            
        match wanted {
            Param::Resolution => {
                matching
                    .map(|(r, _)| Select {
                        resolution: Some(*r),
                        ..fixed
                    })
                    .collect::<HashSet<_>>()
            },
            Param::PixelFormat => {
                matching
                    .map(|(r, _)| Select {
                        resolution: Some(*r),
                        ..fixed
                    })
                    .collect::<HashSet<_>>()
            }
        }
    }
    
    #[test]
    fn q1() {
        let base = Select {
            resolution: None,
            pixel_format: None,
        };
        let bases = which(base, Param::Resolution);
        assert_eq!(
            bases,
            HashSet::from([
                Select {
                    resolution: Some((640, 480)),
                    pixel_format: None,
                },
                Select {
                    resolution: Some((1024, 480)),
                    pixel_format: None,
                },
            ]),
        )
    }

    #[test]
    fn q2() {
        let base = Select {
            resolution: None,
            pixel_format: Some(PixelFormat::RGB),
        };
        let bases = which(base, Param::Resolution);
        assert_eq!(
            bases,
            HashSet::from([
                Select {
                    resolution: Some((640, 480)),
                    pixel_format: Some(PixelFormat::RGB),
                },
            ]),
        )
    }
    
    #[test]
    fn s1() {
        let base = Select {
            resolution: None,
            pixel_format: Some(PixelFormat::RGB),
        };
        let selected = select(base);
        assert_eq!(
            selected,
            HashSet::from([
                Config {
                    resolution: (640, 480),
                    pixel_format: PixelFormat::RGB,
                },
            ]),
        )
    }
    
    #[test]
    fn s2() {
        let base = Select {
            resolution: Some((1024, 480)),
            pixel_format: Some(PixelFormat::RGB),
        };
        let selected = select(base);
        assert_eq!(
            selected,
            HashSet::from([]),
        )
    }
}